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Messages - TrumpetPower!

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Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 07:38:52 PM »
Congratulations! That's the correct answer.  Who are you? start to study the subject then you understand why 2 different yellow hue is better than one,  the time is now 00:59 and we can discuss this subject as much you want. keep your messages short and concise.
and and stop being rude to people who have  knowledge and requires three sentences instead of a bunch of bladder bludder
Talk to Lindbloom as  you referar to and you understand why there will be less errors

nighty nighty and cheers

Mikael, you are so hopeless I wonder why I bother.

First, you demonstrate the most appalling ignorance and incompetence. Then, when I and others correct the misinformation you spew, you never actually attempt to address any of the points I or anybody else makes, and instead you keep beating your same old tired Nikon DR / DxO / QPcard drums, always without content with any more depth than "two stops more physics better."

Who I am is utterly meaningless. Address my facts or not at all.

You'll notice that I'm not similarly challenging you, Mikael, to provide your own bona fides. Even if you've got a PhD in DxO, who you are is meaningless. It's your ideas that matter here, and your ideas suck almost as much as they're incoherent.

I've repeatedly explained in great detail why the gamut of the target is so important, even going so far as to include an example of somebody who uses a virtual target with the largest theoretically possible gamut. That you're suggesting that I haven't explained the importance of target gamut size -- that you're probably still not aware as you read these words that I just explained the importance of the choice of the yellow patches in question -- just goes to show that you're so far out of your league that you're the poster child for the Dunning-Kruger effect.

Really, this is every bit as bad as your attempts to "compare" dynamic range with an architectural shot completely devoid of detail because it was grossly unfocussed and shot at f/1.4, presumably hand-held. I keep trying to bring you up to speed on the most basic of matters, things that you absolutely must know to even be able to understand the discussion -- let alone contribute to it -- and all you can do is whine that I'm trying to tell you too much about things you don't understand.

I'm sure I've told you before about the First Rule of Holes. Your reputation here really couldn't possibly get worse, so even it might no longer apply...but, really. You're in the deepest hole I've ever seen an Internet troll work himself into, and yet you still keep digging as fast and furiously as you possibly can. Do you really think you're going to escape to China that way or something equally bizarre?



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 06:21:56 PM »
passport has higher saturated yellow color

Congratulations! That's the correct answer.

It's also, incidentally, the answer for the rest of the saturated patches as well.

and it has no meaning in terms of measurement

BZZZZT! Worng answer. Very, very, very, very worng answer.

Profiling is all about sampling the color space. The larger the sample space, the more sample points, and the greater the density around critical areas, the more the model can know about the behavior of the device. The more saturated the colors in the target (for those colors at the edge of the sample space), the larger the sample space and the less extrapolation the model needs to predict the response of even more saturated colors. Colors within the volume encompassed by the ColorChecker will be pretty accurately known but will have to be guessed at through extrapolation if you use the QPcard.

Indeed, there are people who are getting superlative profiling results using a tunable monochromatic light source and no lens -- and, obviously, not using traditional targets! (And, since I have no doubt but that you have no clue what that sentence means, it means that they're generating perfectly pure, perfectly saturated colors using some very expensive equipment and photographing the colors the instrument generates one at a time and building the profile from measurements of all the images of all the different purely saturated colors the instrument can produce.)

have you tried  if you get better accuracy with passport than with two yellow hues in op-card?

Why would I waste money on such a clearly inferior product sold by people whose marketing departments (and probably engineers) are clueless about color science?

ps Lindbloom knows what this means, less metamerism errors

Thank you for demonstrating that you have no clue what "metamerism" means and its application to color profiling.

The only way that you could generically deal with metameric mismatches would be if you were capturing complete spectral information -- ideally of the metamers themselves, though you could fake it pretty well with a camera and a spectrometric recording of the illuminant.

Which is why it's not even pretended to be dealt with in ICC profiling. Instead, you just build a profile with an image of the target taken in the same illumination as you're shooting in. If the camera is reasonably close to satisfying the Luther Condition -- and all modern cameras are, though none (of course!) is perfect -- and your target is good enough (and neither the QPcard nor the Passport have nearly enough patches to really do this right, though the Passport is significantly better while still being inadequate) then the profiled image the camera makes will match the appearance of the metamer in that scene.

Can you then transform that image to simulate different viewing conditions? Of course not! Not without complete spectral readings and some very sophisticated math. There are folks at the Smithsonian who could do it, but not very many others.

However, with a well-profiled image, you can then make a print that, when viewed in standard conditions will match what the original scene looked like. And, if you can get a spectral reading of the original scene, you can make another, different print that will match the original scene when viewed in those conditions. But -- again of course -- since no printer uses (significantly) metameric inks (for very good reason!), you're obviously not going to get a single print that would match the original objet in any lighting.

Really, why it should even occur to you to bring metamerism into this is beyond me. Or did you just latch onto the first strange-sounding word you came across in a random Google search and hoped it'd somehow confound me and get me to stop pointing out your ignorance?



Lenses / Re: 50mm 1.2L vs 35mm 1.4L for events photography...
« on: April 25, 2013, 05:48:03 PM »
I'm surprised nobody's mentioned this.

Use one of those EXIF analyzer tools to figure out what focal length you use the most. Buy the lens closest to that focal length.

And, as others have mentioned, the Sigma 35 and the Canon 50 f/1.4 both deserve serious consideration. Don't automatically assume that the Canon red ring means it's the best lens, or especially the best lens for your purposes. The red ring generally means it's a very good lens...but, in the case of the 50s, the 50 f/1.4 is 90% as good as the L at a quarter of the price, giving the f/1.4 perhaps the best price : performance ratio in Canon's lineup and the L the worst. If that last 10% means something to you and is worth a thousand bucks (and you can afford it), by all means, go for it. Just go for it with your eyes open.

And the Sigma really does appear, by every account I've come across so far, to be marginally better than the Canon in pretty much every way that matters. Not enough better to warrant selling the Canon (unless you're desperate for cash), but certainly enough better to warrant buying the Sigma instead. Some are worried about future compatibility citing some infamous past problems, but with that USB dock that's also a non-issue. Long-term resale value might still be a concern, but that's a moot point if you buy your lenses to use for photography as opposed to financial investment instruments.



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 05:20:25 PM »
trumpet Power, as usual you mix many things, and why are you writing so long text, no one can follow you, that the people behind qp-card dont know what they are doing, well that is sure a statement from your side.

who are you?

<sigh />

So sorry for confusing you with things like facts and details.

Let's try something simple.

That page you linked to has reference files for the QPcard.

Robin Myers did a superlative review of the ColorChecker Passport that you can read here:

He includes even more information about the Passport in his review than QPcard does on their Web page.

Compare the D50 Lab values for the two. Which chart has the most saturated colors?

Here -- I'll make it even easier for you.

The lower left patch on the QP203 is a saturated yellow. According to their reference file, it's L*=86.1, a*=5.2, b*=80.7. The ColorChecker Passport includes a similar yellow, third from the bottom on the leftmost column. According to Robin Myers (whose numbers very closely match my own measurements), it's D50 L*=87.02, A*=3.38, b*=86.80.

Which of those two colors is a more saturated, more pure yellow? Which is farthest from the neutral axis and closest to the spectrum locus?

That isn't a difficult or confusing or advanced or misleading or tricky question. It's not that different from asking which lens is faster or has the most reach.

If you know enough about color to answer those questions, we might be able to have a productive discussion. If not, kindly stop pretending you know so much about color -- and please stop pretending you know enough about color to evaluate the claims of the QPcard marketing department.



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 04:47:32 PM »
you have many remarkable statements ,   and what do  you know about the color fields  in qp-card  and how they are  produced? .   In reality Profoto handle all colors and nuances  except some cyans in mathematic model and who have no interest .

What do I know about color? Not much, granted -- especially in comparison with true digital color scientists such as Graeme Gill and Bruce Lindbloom. But I know a hell of a lot more than whoever wrote that page you link to, which has real doozies like this on it:

Manual white balancing, using a neutral gray target in the scene, is the best way to achieve neutral grays in the picture. However, it doesn't matter if the gray target is manufactured by Kodak, Datacolor, X-rite or QPcard; the end result is the same.

First, using a chart with a single gray patch on it to achieve gray balance is, by definition, the worst possible empirical method for the task. A chart with two gray patches is much superior, and a full-sized color chart is ideal.

Second, the notion that the manufacturer doesn't matter and that all produce the same results is ludicrous. If you are going to use the click method, the uniformity of the spectral reflectivity of the target is paramount, and none of the targets on the market are as spectrally uniform as even a styrofoam coffee cup. (Well, with one notable exception: anything from LabSphere made of Spectralon. But those targets cost as much as an L lens.) I know -- I've got many of them and I've measured many of the rest with a spectrophotometer. I've actually got a can of paint from Home Depot that's much better than average, thanks to a helpful response to a query I made to their technical support group.

Anyway, that's just the easy and trivially obvious misinformation on that page. They also suffer from misconceptions such as this:

The color samples are divided into four groups. The primary groups have 9 saturated samples of red, green and blue picked to accurately determine the spectral midpoints of the on-sensor filters.

It's a nice-sounding idea, but completely worthless. Neither ICC nor DNG profiles give a damn what the spectral midpoints of the filters are. If you had a complete map of the complete spectral sensitivity of each filter, you could probably generate a model of the camera's response well enough to create not-bad profiles from that information...but you'd need not just the spectral midpoint but enough other points on the curve to plot the entire thing. The green-filtered photosites are sensitive to red and to blue light, but not very sensitive. Knowing how sensitive they actually are would be essential to the type of modeling they're trying to make you think they're performing (and that perhaps they themselves even think they're performing), but you're not going to get that in any useful form from photographing the chart they're selling.

At best, they're well-intentioned but not very clueful. Maybe they're trying to reinvent the wheel without bothering with learning the fundamentals. Or maybe whoever is writing their marketing materials is clueless. Or maybe they're just blowing smoke up everybody's asses with technical-sounding bafflegab and a run-of-the-mill product.

Regardless, you've fell for their hype, hook, line, and sinker.

Considering that your knowledge of color science is so limited that you aren't aware of all the quantization and color shift and other problems associated with ProPhoto, it's not surprising that you'd be taken in by that kind of salesmanship. Color science is a deep and obscure field, and it's easy to get confused, which makes it even easier for people to intentionally or unknowingly confuse others, including for personal monetary gain.

But QPcard truly is, at best, a run-of-the-mill product. That the hype surrounding it makes it seem like the greatest thing since sliced bred when it truly isn't is enough reason to not give them any financial support by buying their products, even if they're truly sincere about the hype.

If you want a better color target than any you can buy today, it's not hard. Start with a classic ColorChecker; take it to your local paint store and have them match each of the colors. You might need to go to the newest paint store in town, as some of the colors are too saturated for those with older formulations to match. But the matches will be good spectral matches within the observed variation of the official targets over the years.

Next, go to your local art store and get a sample sheet / book / whatever of artist's paints. Golden Fluid Acrylics works well for this purpose, but they're hardly the only ones. Measure the samples with your spectrophotometer and pick a dozen or so samples with a representative mix of spectra. Buy those paints as well as a bit of white.

Now lay out your chart in Photoshop. You'll want the ColorChecker somewhere in the middle. You'll want each of your artist's paints in a few shades (mixed with white). You'll also want a number of patches that you'll print, including a dozen or so neutral patches as well as at least a hundred, preferably twice or more, patches distributed uniformly throughout perceptual space -- and, obviously, you'll need to have a good profile of the printer and paper you'll be using to generate that patch set. For bonus points, include a bit of PTFE thread tape for your whitest patch, a black trap (make the target a hollow black-lined box with a patch-sized hole for your darkest patch), and samples of real-world objects you'll care about (such as wood chips).

Print the target, paint in all the paints you've assembled, let it dry a day or three, measure the patches with your spectrophotometer, and build your profiles.

If your paint store will sell you pint-sized samples and if you're friendly with an artist who'll let you use her paints, you can build for yourself a color chart that puts everything on the market to shame for not much more than that QPcard will cost, of course, a significant investment in your own time....



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 02:20:11 PM »
What do you mean, Pro Photo  can reproduce all  colors without clipping and you can then  proof in  ProPhoto  color space into a smaller profile/color space as Adobe RGB and then convert to Adobe RGB with good results

Eh, no. Not even vaguely close.

Look at either a CIE chromaticity diagram of ProPhoto -- or, better, a 3-D gamut plot that includes the spectrum locus. Huge swaths of color lie outside of ProPhoto's space...and, worse, ProPhoto's space encompasses huge swaths of imaginary space, colors that simply don't exist.

If you want a much more useful working space, try BetaRGB. No imaginary colors, encompasses all of AdobeRGB, encompasses most of all real-world output devices (which AdobeRGB doesn't), and otherwise very intelligently designed.



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 02:10:31 PM »
The Swedish Photographer ASSOCIATION  did a test of different reference card and software, best was QP-Card

You keep flogging the QPcard. Honestly, it's not all that impressive. A mere 35 patches to begin with...and then they cluster all the patches in small clumps in device space, effectively wasting over half of the patches. A more uniform distribution in device space would produce far better profiling results as you'd sample a much larger portion of device space.

That's what the Passport does. The classic 24 patches are already pretty well distributed in device space. Then you've got all those saturated patches that probe the boundaries of device space; the QPcard doesn't have any saturated patches, meaning it's just sampling the center of device space.

And then the Passport has a number of near-neutral patches that they market for the purposes of creative white balance, but which actually provide tight clustered sampling around the neutral axis, which is perfect for triangulating white balance and one of the two times you're really at an advantage for multiple sample points in a small space when building generic profiles for a device with unknown characteristics. The other, of course, is for neutral points at the extremes of the dynamic range so you can closely probe the shadow and highlight portions of the response curves -- and, hey-presto, the Passport has those patches as well!

Now, might the QPcard DNG profile-building software suck less than the Passport DNG profile-building software? No clue. Don't care. DNG profiles are worthless, sorry jokes when it comes to color management; by the specification's very design and stated intentions, you're never going to get anything close to accurate color out of them. They're meant for "pleasing" color -- and "pleasing," by definition in this case, is in the eye of the software developer writing the profile-building code. And "pleasing" on said software developer's own monitor in said software developer's own office, neither of which is likely to be set up for color critical work.

And, similarly, you're never going to build a quality LUT input profile with a target with only 35 patches -- and not even with the mere 50 patches of the Passport. You need at least a few times as many patches for critical work, and you're just not going to get that in a small, portable target.

But that small, portable target can get you a high-quality matrix profile that you either use to set white balance and exposure or that you apply before applying your studio-created large-patch-count LUT profile.

And, for that, the Passport is very significantly superior to the QPcard. Dramatically so.



Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 01:49:19 PM »
But for me I'm not looking to have 110% right
Color for everything.

Then, in that case, I'd suggest a simplified version of what I described.

First, don't create DNG profiles on the fly for every shot. Instead, create a few carefully-constructed DNG profiles for the types of lighting conditions you care about. Pay particular attention to getting the chart evenly illuminated and avoiding anything that might reflect a color cast onto the chart. A light tent is great for this sort of thing.

When you shoot, still shoot the Passport. First, if you ever do go to a more refined workflow, you'll be able to use that image of the Passport as I described. But, more immediately, you can eyeball / eyedropper the passport to get the proper white balance and exposure much better than you can a simple gray card.

First -- after, of course, selecting your pre-canned DNG profile -- crop the shot to just the Passport. Then, set a preliminary white balance with the eyedropper on the gray patch next to the yellow patch. Now, adjust exposure until, by the numbers, the neutral patches are as close as you can reasonably get them, paying more attention to the midtones than the shadows and highlights (both of which are going to get mutilated with Adobe's rendering engine whether you want them to or not). If nothing else, get the N5 patch to read close to 118/118/118. Then, crank the saturation as high as it will go and fiddle with the white balance until the Passport looks as close to normal as you can. Return the saturation to normal, and double-check that the exposure is still where it should be. If not, repeat both exposure and white balance adjustments. When done, and only when done, you can then move on to the creative adjustments (if you're so inclined).

And don't forget that you're never going to get correct color with clipped highlights...and that Adobe's tools do all sorts of hidden black magic to protect you from clipped highlights so you may well not be aware that they're clipped. There are lots of free tools that'll help you analyze raw files; run your problem images through one or two of them to see if there's any clipping in the raw files themselves. more thought.

All the working spaces, even Lab, have limited color gamuts. It could well be that the raw data isn't clipped but that the colors lie outside of your working space -- let alone your monitor's or printer's color spaces. Try again with ProPhoto, which has all sorts of problems but at least encompasses all output devices you'll be able to work with. Even if that solves the immediate clipping problem, your troubles aren't're still probably not going to be able to output that color, either on your display or in print, and now you've got to deal with Adobe's substantially suboptimal profile conversion routines and hope that their perceptual rendering doesn't just wind up clipping the colors anyway.

Again...good luck....



Why would a professional photographer use a point & shoot as a backup? If I'm shooting a wedding with a 5D3 as primary equipment, what would a point & shoot do for me if I have a problem with the DSLR?

If I'm a photojournalist with a DSLR and a 16-35 or 70-200, what would I do with a point & shoot?

My thoughts exactly. When I'm shooting with the real gear, it's because the iPhone simply isn't going to cut the mustard. In fact, it's not even going to come close.

Might I still whip out the iPhone for a snapshot? Sure -- but mostly just to email a teaser to friends and family on the fly. "Hey, I just made it here to the Grand Canyon. Here's a snapshot of some pretty patches of snow on the cliffs. Can't wait for the Sun to set and the comet to come out!"

If you need backup gear, it should ideally be a duplicate of the real gear, and otherwise no more than one step behind -- though what constitutes a step is going to depend on your particular application. A Rebel-series camera could serve as a suitable backup for a 1DX in some very contrived scenarios, but, more realistically, you'd be looking at a 1DIV or a 5DIII as your backup for the 1DX.

Now, might a mirrorless / P&S / iPhone make a useful supplement for certain types of gigs? Sure. I already mentioned my use of an iPhone to keep friends and family in the loop; I could see a professional landscape / travel photographer making quick blog posts similarly to keep interests up while on the road. If you're not printing too big, some of the P&S cameras make great landscape cameras, especially considering how small and light they are; indeed, they're awesome for scouting expeditions. The EOS-M could make for some really interesting event photography where you wanted to be inconspicuous.

But as replacements for the main gear?




Lenses / Re: Aperture and Light
« on: April 25, 2013, 10:45:40 AM »
The II-version has a lower T-value, measured by dxo.

Look at "transmission".


The old version has perfectly constant transmission across the entire focal length range. The new version is a lot brighter at the wide end but winds up almost as dim as the new version at the telephoto end.

Seems to me that the old version is going to remain the favorite of the cine crowd....


Software & Accessories / Re: ColorChecker passport, what's wrong?
« on: April 25, 2013, 10:38:28 AM »
So, a few things.

First, the Passport is an excellent small and portable chart for field use.

But the DNG profiling software simultaneously sucks and blows, and that's not a compliment.

The first half of the problem is the DNG profiling software's fault: it only uses the classic 24 patches when building profiles; it completely ignores those other 26 patches. Considering that those other patches include both some much-more-saturated patches that really help define the camera's response as well as a number of near-neutral patches that really help nail down where the neutral axis (and therefore white balance) lies, that omission is both incomprehensible and inexcusable.

The second half is Adobe's fault, and that's the incoherent mess that is the DNG color "profiling" process. It's not even remotely theoretically possible to get anything vaguely resembling colorimetric accuracy from DNG profiles, though you can fake it by manually tweaking a DNG profile to be as close as you can get it and then build an ICC profile on top of it. Basically, if your idea of "good" or "pleasing" color means no-holds-barred impressionistic interpretations of color, DNG is for you. But if you want an accurate representation of color, DNG is a cruel and unusual tool for extraordinary rendition.

If you care about accurate color, you simply cannot use Adobe products to develop your raw files. Nor can you use many of the other popular raw development engines, such as Canon's DPP, because they suffer from the same root problem: the programmers have decided that their taste in color palettes is best for you. Accurate color, hell -- you can't even stop any of these raw developers from applying a contrast-boosting (and detail-obliterating) S-curve!

It's a real shame, too, because the hardware itself is quite readily capable of superbly accurate color reproduction. There's no reason why accurate color shouldn't be the default starting position, always available as an option, with the various "secret sauce" recipes only optionally added on top.

So what you're left with is mostly tools that come from the Free / Open Source software crowd, some of which produce superlative results but none of which have user interfaces with the spit-n-polish that Adobe products have. That is, you can use Adobe (etc.) products which are beautiful to look at but which mangle your own images, or you can use other tools that are ugly to look at but which make your own images shine.

If you go that route, you'll want something which is at least loosely based on dcraw for its development engine. My own runaway favorite is Raw Photo Processor, but there are other good options.

And your basic workflow would be to first create high quality quasi-generic ICC profiles in carefully controlled situations. The ColorChecker Passport, as useful as it is in the field, really doesn't have enough patches for that kind of work. There are other charts available for purchase that are usable, but I personally made my own chart; it has a replica of the classic 24 ColorChecker patches, another couple dozen paints, a black trap, some PTFE thread tape, a dozen or so wood chips, and a couple hundred patches printed on an iPF8100. I have some plans for a second version, but it's served me well.

Of course, you'll need a spectrophotometer to build the necessary reference files for any chart; there's enough batch-to-batch variation with any manufacturing process that you'll want to measure your actual chart, even if you buy it from a reputable source. The i1 Pro is an excellent tool for this purpose.

You'll also need software that lets you build these kinds of profiles. X-Rite doesn't include that with the software they bundle with their consumer-level instruments, but they do sell some very good and very expensive software that would work. However, if you're not afraid of the command line, ArgyllCMS produces absolutely amazing results, is free, and is superbly supported by the author on a mailing list.

So, you'd build profiles for each camera with the light sources you most care about; one for each of the camera's pre-canned white balance settings is a pretty good idea. And you might even want to consider building one such profile for each lens, as different lenses have different color characteristics.

Then, when you're shooting, you'd include a shot of the Passport as usual. When you get back to the studio, you'd do a linear gamma UNIWB development of that shot -- basically, just dump the raw file completely unmodified to a TIFF. You'd build a matrix profile from that and do a reverse lookup of D50 white, which will tell you what per-channel multipliers you need both for white balance and to normalize exposure. You'd then use those figures when developing the real shots and apply your most-appropriate custom-built pre-canned ICC profile.

That'll get you as close to perfect color as you're going to get with a DSLR. And, indeed, said color is good enough that, if you've got a similar workflow at the printing end of things, you can make copies of artwork such that the artist herself has to stare a long time at the original and copy side-by-side to be able to spot the differences -- the gamuts of the original and your printer permitting, of course.

One other're having problems with reds and you're mentioning problems with overexposure. Some cameras, especially older ones, are notorious for overexposing reds, especially reds rich in infrared such as flower petals in sunlight. It's impossible to recover an overexposed image, no matter how good your profiling software.

What you can do, however, is underexpose the image sufficiently to prevent the reds from blowing, and still use the Passport to determine how to normalize the white balance and exposure in post. You're essentially applying digital ISO boost in post-production at that point so you have to be careful of noise, but you can boost a 5DIII ISO 100 exposure by a half-dozen stops in post if you're careful so it's not as much of a concern as it used to be.

Good luck, and may the Farce be with you....



Lenses / Re: Aperture and Light
« on: April 25, 2013, 09:49:41 AM »
I just got the new 24-70 to replace my Mark I version of the lens.  Here is my question, given that the new lens has a diameter of 5mm more, does that mean that more light enters the lens?

Any differences there may be will result in negligible changes to exposure. Indeed, if you look at the actual specifications of pretty much any lens, you'll see that the numbers on the barrel are all rounded. A 200 mm lens might actually be a 193 mm lens; an f/4 lens might actually be an f/3.87 lens; and so on.

In addition, glass (and fluorite and the other materials used to make lenses) doesn't transmit 100% of the light coming through. Each lens element absorbs some of the light. A lens might have a focal length : aperture ratio of 1 : 1.4, but the amount of light that makes it through to the camera might only be as much as an impossible theoretically-perfect f/1.8 lens.

Since most people shooting SLRs use the camera's through-the-lens metering and because modern DSLRs have so much dynamic range and therefore exposure flexibility in post-production, those minor variations are insignificant in the real photographic stills world.

However, they are of concern in the motion picture world, where you've got multiple cameras shooting the same scene from multiple angles and whose resulting images will be composited together in such a way that even minor variations in exposure will be apparent and distracting. And that's why cinematography lenses are calibrated in T-stops instead of F-stops. The T-stop is a measured number of the actual light that makes it through the lens. You might have a lens that, as in my previous example, has an F-stop of 1.4 but a T-stop of 1.8.

It would be interesting to compare the T-stops of the two versions of the 24-70, but really only useful if you're a cinematographer. And I'd be surprised if the two of them differed by more than a third of a stop.



Would be nice if this has AF. I love my 35mm f2 Zeiss on my RX1 - solid & sharp.

Will wait for rumor Sigma Art 135mm f1.8 OS ;D

Hi Dylan777, but I think (not sure) the Sigma Art 135 f/1.8 is designed for APSC ?? I use FF (Except I do still have a 1DMK IV), so may not be of much use on FF, but I do own the Sigma Art 35f/1.4 and I find that a very good Lens.

In Sigma Langua DC=APSC, DG=FF so the party is on!

...except, of course, that the Sigma lens is only a rumor, with no official announcement from Sigma.

(Which, incidentally, is exactly how Canon should have handled the 200-400 but didn't....)



IS is nice, if you can afford it...

Agreed...but, when shooting sports, you're going to want to keep the shutter at least in the 1/500 and above range to stop subject motion, and you need some pretty bad Parkinson's for IS to make a visible difference at those shutter speeds.

That's also why you want the fastest lens you can get for sports, so you can get the fastest shutter speeds. An extra stop of lens speed means one stop lower ISO setting, basically. That's not very important outdoors on bright days, but it quickly becomes a factor when the clouds come out and it's your overwhelming concern when the Sun goes down.

...but, of course, ISO speed is closely tied to what you're doing with the image. If you're just posting small pictures to FaceSpace, you can get away with much high ISO settings than if you're a stringer for Sports Illustrated.

There's one other caveat that I've gotta bring up. Those SI guys generally shoot with two lenses on two bodies, and for a very important reason. The secondary setup is with a 70-200 f/2.8. The primary setup is with a 400 f/2.8. They're right there on the sidelines, as close to the action as you can get without being part of it, and they still need 400mm lenses to get the shots they do. The 70-200 is what they (quickly) switch to when the action moves to right in front of them, but most of the time they're using the 400.

So, again, if you're not looking for something to make posters with and if you're not in the nosebleed section, you can shoot from the stands with a 70-200...but you should plan on heavily cropping every image, and you should expect to have the lens always at 200. And you'll especially want the fastest lens you can get, because cropping exaggerates high ISO noise at the same time it makes the image softer.

If, indeed, you are shooting from the stands...well, first, I'd suggest that you adjust your expectations accordingly. And then I'd suggest resigning yourself to the fact that you're not going to get great images no matter how much you spend. And then I'd suggest preparing yourself to be disappointed even after spending lots of money. Starting to get the picture?



Lenses / Re: 300 f/2.8L and 400 f/2.8 at f/2.8
« on: April 24, 2013, 07:21:56 PM »
Carl, your difficulties with autoexposure are exactly why I never use it. Though, granted, I rarely shoot in light that changes very fast.

If you're shooting outdoors, unless it's a partly cloudy day with fast winds aloft, chances are good that autoexposure is going to be much more trouble than it's worth. The light just doesn't change fast enough that you can't keep up with it just fine by yourself.

And at least the full-frame cameras these days have so much dynamic range that, so long as you're shooting raw and the exposure is in the ballpark and you haven't clipped highlights you actually care about, you can recover almost anything.

(If you've missed the exposure by several stops, or if you're looking to turn shadows into highlights, or any of the other insane and wacky things the D800 fans keep bragging they can do, you might have problems. But otherwise, exposure these days is very forgiving, especially at lower ISO settings.)



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