November 29, 2014, 05:07:03 AM

Show Posts

This section allows you to view all posts made by this member. Note that you can only see posts made in areas you currently have access to.


Messages - sarangiman

Pages: 1 [2] 3 4 ... 25
16
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 05:09:44 PM »
Shoot a transmission step wedge. Note the number of gray squares. Keep down sampling it until a black square turns gray. Or, if you prefer, make a really big print and keep backing away from it until black squares turn gray  ;)

Down sampling does not change the range of tones you have. It allows you to reduce the impact of noise and thereby better detect finer detail that is composed of the lowest tones. In that sense you are extending the usable range a bit. But that is all.

Yes it does. It changes the range of usable tones by making darker tones more usable.

You yourself said it: 'reduce the impact of noise'. Reducing noise = increase in SNR, which can lead to an increase in DR.

It'd help if you properly understood what dynamic range is, and how it's calculated, before you went around misinforming people here.

Note: noise can be so severe that it obscures the last patch or two of gray in such a test, whereby downsampling would reveal them. But there's not any where near that much noise at base ISO on any of these cameras.

Clearly you've never shot an actual 13 stop wedge with a Canon DSLR, if you haven't seen any unusable patches with so much noise that SNR drops below 1 or 2. It's not even the last one or two patches - the last ten or so patches drop below SNR = 2 for a Canon 5D III, at the pixel level. Normalized to 8MP it's a little better.

And that's the whole point of normalization. It even helps your beloved Canon sensors. :)

17
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 04:33:18 PM »

No it wouldn't. The difference between the lightest light and darkest dark would be identical so the DR would be the same.

Quote
Dynamic range, abbreviated DR or DNR,[1] is the ratio between the largest and smallest possible values of a changeable quantity,

The largest and smallest values are constant, there is, and can be, no change in DR.

The averaging you are talking about does not result in 'more DR' it results in a greater number of values within that same range, or put another way, greater tonality that is so small in increments it is beyond our eyes capacity to differentiate.


This is where you're going wrong.
 
The 'smallest possible value' is defined by the signal that is just above your SNR threshold (just above the noise floor).

Averaging increases SNR, so darker signals now make it up to your SNR threshold. So you've now increased your range of usable signals or tones, and therefore DR has increased.

Do a side-by-side with the D600 and D800 at equal viewing sizes. Do you really think the D800 has worse DR?

Perhaps a good exercise would be for you to actually measure DR by doing some SNR analyses from wedge shots yourself before you so confidently talk about this stuff? I'm being serious, not trying to be rude. You seem to almost have a grasp of this stuff, and feel you would finally 'get it' if you did some analyses yourself.

18
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 04:27:17 PM »
What it won't do is have a brighter bright or darker dark, and surely that is the measure of DR, not how many divisions that same range is divided into?

No, sensor DR is the difference between the brightest bright it can record (where it clips) and the darkest dark that is not lost in noise.

But surely, if each pixel has the same well capacity, even though the smaller one performs 'better' for its size, the range of light they can both accurately record is the same, therefore the 'true DR' of the sensor* is the same, for instance the highlights will be blown at the same photon numbers.

*True DR would be the difference in light levels between a pixel that only registers black, to when it is full such that one more photon will not register.

Here you're not considering that when you downsize, you average pixels, which increases SNR for the area of pixels averaged. And you do know that areas with SNR < 1 can reach SNR = 1 with enough averaging, right? Therefore, darker tones can be pulled up to SNR = 1, and therefore calculated DR can increase.

Normalization is a nice way of comparing different things, but it doesn't reflect true DR recording capacity, and truthfully shouldn't be labeled DR. This is one of the many reasons there is such a difference of opinion between people who love tests and equations, and people who look at the differences in images.

Nonsense. There are those that can do both: love the math, and correlate the science/math to image quality differences. There's a reason for controlled tests - when done right, they reflect real-world differences in actual images.

Those in sensor design know this.

Noise and banding is what truthfuly diffentiates the current sensors, and that difference is nowhere near this mythical 3.1 stops of "DR". People that regularly use or work files from both know the differences are in the shadows and are closer to two stops, Canon files can be lifted 3 stops in the shadows with very high quality results, Exmor files can be lifted closer to five stops in the shadows but by the intrinsic nature of gamma curves lose a lot of tonality if you need to do that.

Again, no. Do the proper side by side, and it's not a 'mythical' difference. But you have to know how to do the test right. I.e. don't confuse photon shot noise in an exposure 3 EV under for sensor noise.

The respectable Bill Claff's data or a higher SNR cutoff shows a difference of 2.5 EV. So now we're arguing about a half a stop?

The point is that there are almost no tones in the 14-bit D810 file that can't be used b/c of read noise. If you can't use them, it's b/c you didn't collect enough light to begin with down there. That's impressive, b/c it means the only way you can really get anything better is to use a bigger sensor. For the same reason that high ISO performance would increase with a larger sensor - collecting more light.

Furthermore, I've said time and again - it's not about 'how many stops you can push'. It's about what particular tones in the 14-bit file you can and can't work with. You cannot simplify it to 'Exmor can pushed X stops and Canon can be pushed Y stops'. That's just dead wrong, if you're trying to be rigorous or quantitative, anyway.

As was evident in a recent post here with A7R RAW files available, large areas of 5 stop lifted shadow detail holds almost no tonality which mitigates the usefulness of the capability. That doesn't mean Canon shouldn't have it, it just means that when we do have it don't expect to get the same results from a 'normal' exposure and an underexposed image that is then lifted to 'normal', tonality does not work like that, and that was demonstrated in another thread here recently too.

Ok, but that has to do with photon shot noise. It's the same reason some people find extremely high ISO shots unacceptable. Because tones are made with too little light. Same with tones down in the depths of the 14-bit file. They're made with too little light.

So basically what you're arguing now is that you want a DR measure with a higher SNR cutoff. That's fine, but just realize what it is you're actually saying.

Pixel peeping, or taking a crop at 100% is frequently done in the practice, and as you mentioned, then we don't see any increase in DR. So why using a normalized value to compare something that can't be seen in the practice?

B/c it's not fair to show this:



... when in reality actual visual comparisons of DR will not place the D800 behind the D600, so the following, normalized comparison is more accurate:



Again, not sure how we could make it any clearer - you normalize to simulate a comparison at the same viewing size. Downsampling decreases noise, which increases SNR, which means lower tones make it up to your SNR cutoff for DR, which means DR has to increase.

No one's arguing anything about the absolute number and whether or not it reflects exactly the DR someone may actually find usable.

But you have to normalize for comparisons.

19
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 14, 2014, 12:00:58 PM »
So the 11.7 and 14.8 are based on the fact that they do recalc the dynamic range into a 8mp detail equivalent? That means, that higher resolution will always have a advantage, just by the fact that the D810 has 36mp and the 5D3 has 22mp. So, even if the sensors are performing the same, only difference of mp, then the highest mp will have the highest normalized figure.

That does say nothing to my opinion. The highest horsepower/weight does only tell me that they have the best comparision over there, but not that it would be the best engine or car. That's just the same in my opinion for the recalculation to 8mp.

However, I fully agree that the D810 is a very nice camera that Nikon placed on the market. But please, don't use figures like that to compare those cameras.

No, you misunderstand.

You say 'even if the sensors perform the same... then the highest MP sensor will have the highest normalized figure.'

Yes, that's right. And it's absolutely valid.

Think about what it means for a higher resolution sensor - of the same size - to have the 'same (pixel-level) performance' (before normalization). A higher res sensor necessarily has smaller pixels, which means each pixel has a smaller FWC (full-well capacity). For that pixel to have the same pixel-level DR, it'd have to have lower read noise than the lower res sensor's pixels.

Therefore, it's no surprise it also has higher normalized DR.

20
The reason ISO 100 on a Canon has roughly the same DR as ISO 400 is because the read noise drops by about a stop with each progressive increase to ISO. Hence the flattening of the DR curve on Canon sensors.

Well, it's not that the read noise drops, it's just that all other data & noise off the sensor is amplified 4x compared to ISO 100, which lowers the impact of the read noise. So even though you're throwing away 2 stops of highlight range at ISO 400, 4x (2 EV) darker signal is now being amplified to be brought up to your SNR = 1 (or what have you) threshold, leaving DR largely the same. Cameras with very little downstream read noise don't need the sensor signal amplified to overcome the 30+ electrons of read noise in a Canon camera.

It is still Exmor...I just think they removed the black point clipping and restored the bias offset. Based on the Nikon hackers who restored the bias offset for Nikon Exmor cameras, the read noise at ISO 100, after the offset was restored, was around 6e-. I think the A7s ISO starts below ISO 100, where it's read noise is a little higher, however at ISO 100, I believe the A7s is around 6e- as well...given the similarities between the A7s and an offset-restored Nikon D800, I think that's all Sony did: stop clipping.

No... the A7S has significantly more read noise at base ISO than the D800, A7R, etc. Also, the A7R has an offset and doesn't clip its black. Yet it has significantly more DR than the A7S. The A7S has a different architecture, which explains why its read noise has two plateaus - it doesn't just drop as a function of ISO. It drops, flattens out, then drops again, then flattens. Something about this architecture lends it more measured downstream read noise, which limits its DR. It's still significantly better than Canon, but not as good as the A7R, the D800/810, etc.

One tricky thing is that absolute extreme ETTR can make processing tricky as most standard tone curves end leaving you with poor highlight separation and a lot of stock color profiles are twisted so you can get weird color tints and problems.

Good point. Probably explains some of the odd colors I see with 6 EV pushes :)

Precisely! You get more room to manoeuvre in. Less restrictions on which combinations to select from to get what you want and need. So it is, indeed, giving more than just technically better rendition on the pixel level, you get that extra artistic freedom to combine settings that's usable.

Now that's just talking too much sense!

Yeah dialing contrast way down and saturation down a little bit is a good idea too, if you want the regular histogram to give a better picture of what the RAW is doing.

Interesting. I've been trying to find a way to get the histogram to better indicate what's happening in Raw, without much luck. Perhaps 'Flat' profile and Adobe RGB on the D810 would be a good place to start. Thanks for the tip.

21
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: October 08, 2014, 03:46:00 AM »
You want a good test case for high-contrast scenes?  Check your local high school's website and see when they're doing their school play.  Bring your cameras with wide-angle lenses.  During the curtain call, shoot a wide shot of the entire stage.

If that's a joke, I don't get it.

22
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: October 08, 2014, 01:47:22 AM »
It doesn't need to be a controlled scientific test. You gather a random sampling of pictures through the day identical in both bodies. At the end you PP and you have injected your style and your skill level in to the test. The results are yours and you have an answer. I am sure you will find along the way that both body has advantages and disadvantages.

Oh, well if that's all you or I wanted, then I already have my 'data' and answer. I shot with the 5Dc, 5D2, and 5D3 for years and have tens of thousands of images from them. And amongst them, I've run into read noise and banding many-a-time.

Since owning the A7R and D810, I've never seen any offensive noise upon post-processing. Ever.

Side note is that when the D800 was first released I investigated this for myself to see what the benefit might be. That was over 2 years ago and the debates were few at first. It is interesting that it has blown up in to such a huge topic.

Yeah, and at this point Nikon/Sony are even building off of that incredible sensor. The D810 offers a half to 2/3 EV more DR than the D800 even. None of the shadows in any of the numerous sunsets and sunrises I've shot so far with the D810 have any offensive noise. I now leave my 4x6 graduated ND filters at home. I'll typically take at least 3-4 shots though so that on the off-chance I want less shot noise in my shadows, I can just layer them in PS and average them. Which, btw, is easier than HDR.

23
Reviews / Re: Canon 16-35 F4 Review vs. 17-40 Shootout
« on: October 07, 2014, 01:12:43 AM »
Graham - nice work!

I must have owned one of those dud 17-40s; no matter how many times I sent it back to Canon, when it came back it'd be sharp in the corners for a few days/weeks, and then go soft again. Or one entire side would go soft and would never really sharpen up until f/18, at which point I'd have softening from diffraction.

The three 16-35mm f/2.8L II copies I tested were just as bad, if not worse.

The 16-35 f/4L IS changed all that - I really, really love this lens.

I'm curious - you had no issues on your A7R? I believe the sensor or mount on my A7R is pretty off, as I have trouble with most adapted wide angle zooms. Meanwhile, the new Sony FE 16-35 on my A7R works quite well, so it's very confusing. Wish I had a few A7R bodies (and time) to test...

I do wonder, though, about adapting ultra wides to the A7R, b/c of all the sensor glass thickness issues Roger Cicala wrote about over at LensRentals...

Anyway, beautiful images as well; thanks for the comparison!

24
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 07, 2014, 12:46:59 AM »
The 5DIII with 35 f/2 IS is a great combo, both for video and photos. For video, the IS is so good that the shots sometimes look like they are on a tripod. Can't do that with Sony or Nikon, and f/2 gives great low light performance as well as shallow DOF.

Not sure why you say 'can't do that with Sony or Nikon'...

Have you ever tried Sony's 'Active' image stabilization? Granted I believe it only works with certain lenses, but the combination of optical stabilization on the lens with digital image stabilization (from accelerometer data, IIRC) leads to such steady shots you wouldn't believe they were shot on anything other than a Steadicam!

Furthermore, Canon's not alone in getting very well image stabilized lenses in their lineup. Although the 16-35mm f/4L IS is quite stellar (rated to 4 stops IS by CIPA standards, which are pretty stringent, so it really is that good), so's the VR on the Nikon 70-200mm f/4 (also rated to 4 stops CIPA). It's incredibly steady. Oh and the Fuji's 50-140mm has the best IS I've ever seen; rated at 5 stops CIPA, it's so good it's a little unsettling.

Actually, I see IS getting better from generation to generation. Generally, the newer the lens, the better the IS. So with Canon putting out so many stellar lenses of late, yeah there may be an advantage there. And no one will argue that Canon doesn't have an incredible lens family. Just that, e.g., for me that doesn't matter much. B/c there are excellent alternatives in other brands. For example, Sigma now makes the best 35mm and 50mm AF primes, hands down, and is brand agnostic. The Nikon 70-200 f/4 VR is much better than the Canon 70-200 f/4L IS, which has serious left/right softness issues that vary from shot to shot b/c of the IS element (even the Sony FE 70-200 f/4 doesn't have this issue). Etc. etc.

And if we're talking about video, the Sony A7S will do far better with those Canon lenses than a 5DIII would... and will still use the IS on those lenses with the Metabones adapter. Btw the VR on the Sony 16-35 is also incredible.

My point being - there are very credible alternatives from other brands that make such generalizations misleading.

25
Reviews / Re: Tony Northrup - D810 vs. 5D Mk3
« on: October 06, 2014, 02:44:13 AM »
I think for most people, pitting these cameras against each other is sort of a waste of time, though it may be interesting to compare how they compare to each other. I wonder how often users are really trying to decide between a 810 and 5D3. This sort of makes the assumption that they don't have any lens investments or are willing to sell their lens collection (probably at a serious loss) to invest in a new system, when Canon could easily come out with a more compelling camera within a matter of months. The only real advantages I see to the current Nikon system is in landscape photography, where the addition of an A7r + lens adpater could be added.

One of my biggest epiphanies involving gear is that you buy a camera for your lenses, not the other way around.

I always find this viewpoint interesting. I sell my lenses all the time. I usually lose something like 10-20% on my lenses, and once even earned 20% b/c the lens had appreciated.

The bigger issue for me is the time involved in selling lenses. Since I test at least three copies of each lens I buy, the time investment really adds up.

The other thing is you have to spend a lot of time learning all the quirks of the new system. Sometimes this can be a good thing, but it can also be daunting and, who knows, you may end up finding a particular set of quirks that ends up making the whole switch a wash. :)

26
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: September 27, 2014, 04:26:41 AM »
With exmor sensors you don't even have to bother thinking about getting the optimal exposure, you can focus on the other stuff and just shoot.

Yeah, I totally agree. I always have to get just the right amount of ETTR with the 5D III, so I'll usually (with landscapes, I work it a bit different with birds and wildlife) take a couple test shots to make sure I have the exposure right. With the A7r, it just isn't an issue...get the exposure generally right, take the shot. If your off by a third of a stop, either over or under exposed, it doesn't matter. You can usually recover it either way.

Now this is just crazy talk. Stop making excuses for being lazy and sloppy. You should learn to focus on everything all at once. You should even manually focus, like the pros did decades ago. And make sure you don't leave any more than 0.5 EV highlight headroom and then try to show there's noise in the shadows - you'll be lambasted.

Ok, on a more serious note: isn't that what I've been trying to say all along? That equipment getting out of the way opens up creative potential?

Anyway, make sure you don't take 'don't have to bother thinking about getting the optimal exposure' too far... actually depriving the sensor of light (via faster shutter speed or smaller aperture) does cost you image quality, no matter what sensor.

But, yes, it's a very 'free-ing' thing to not have to worry about excessive read noise - generally the only cost you'll pay by underexposing with Exmor is image detail that just looks like it was shot at a higher ISO. And that's usually not exactly devastating, given the ISOs people willingly accept shooting at these days.

27
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: September 26, 2014, 11:51:15 PM »
I for one would be interested in seeing comparisons of pics taken in real situations that photographers face.
The shooter draws a conclusion, provides the RAW files and anyone can see if they draw the same conclusion.

This would be much better than the pointless technical banter that never proves anything or goes anywhere.

This is a very fair, valid request. A little difficult to do, but very worthwhile. What makes it hard is that it's actually very difficult to find sunsets/sunrises that do bottom out a, say D810. So it's hard to show the real difference, i.e. 'what's possible'. And if you do find the right high dynamic range scene, you're probably a landscape photographer who woke up at 2:30 am to shoot a sunrise at a beautiful location, not do a head-to-head test which is fairly challenging to do with the quickly changing light of a good sunrise/sunset. You also have to bracket both cameras all over the place so that you can go back home and then find the one where the highlights are just short of clipping, or where ACR can recover detail/color to taste.

I'm not saying it's impossible, it's usually just hard to do well. Hopefully someone will do it (well). I'll try at some point, maybe, before I sell off my 5D3.

...so here I am. Trying to be a man of my word.

I respect that. Good luck!

28
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: September 26, 2014, 08:23:29 PM »
So it seems the reason I've been seeing posterization issues and Sarangiman hasn't when doing the emulated high ISO trick is due to Sony's compression algorithm.  Good to know I'm not the only person seeing this.

To be fair, I rarely see it with my A7R, so I think some of it may be due to your use of the A7 (IIRC)?

But, yes, Sony's compression is very, very annoying under certain circumstances. And that's a great reference/study you linked to, by the way.

29
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: September 26, 2014, 06:23:49 PM »
I don't need a novel, I need a cohesive thought that can be backed up with supporting information. You think you know but you don't, you think you can explain but you can't, very convincing........

What don't you understand about RGB values in the low single digit percentages being shadow detail?

Why are you still talking about percentages on a histogram that represents the Raw values converted to ProPhoto RGB internal space and then converted to sRGB output and then converted to a percentage?

I analyze *actual* Raw numbers using RawDigger. Quit convoluting this analysis. I don't even know what your point is anymore.

My point is that you can't just do +3 or +4 EV pushes for these sorts of comparisons on brighter tones to demonstrate the differences. If you don't see a difference, you're not pushing deep enough shadows. If you don't have deep enough shadows while you're exposing for highlights, then your scene doesn't have enough DR for it to matter whether or not you're shooting Exmor or Canon.

I never said it's just about how many stops you can push. It's about what tones you're pushing. You seem to be stuck on this 'but XYZ percentage *is* a shadow'... what? First of all, what's a shadow depends on your exposure, and second, my signal of 7 out of 16,000 on a linear scale would be 0.04%. So, no, single digit percentages don't impress me.

I think I know? Not even going to respond to such a patronizing comment considering I do full SNR analyses of sensors...

30
EOS Bodies / Re: Just for Jrista: 2014 Market Data
« on: September 26, 2014, 05:13:09 PM »
No it wouldn't, a +100 shadow lift is a +100 shadow lift, it doesn't matter where the highlights are, or even if there are any. The entire image is as irrelevant as it was in sarangiman's crop which all the DR'ers thought was "amazing", see what you are doing here? Trying to make what you want/expect to see fit into what you actually do see.

This is completely misleading. A +100 shadow lift is not just a +100 shadow lift as you're implying. Whether or not you see banding/noise depends on where the tones you're pushing initially resided in the 16-bit Raw file.

It's pointless to have any other discussions until you at least appreciate that.

Unless you can explain better why that is misleading, after all the RGB values increase exactly the same numbers as an exposure slider lift does, then I agree, you and I have nothing to discuss.

What, specifically, is misleading?

It's not just about the amount of the push. It's (the signal of) what you're pushing.

And, no, I'm sorry, I don't have time to write a novel on this right now. Honestly, I'm not being snarky. Perhaps someone else can explain.

Pages: 1 [2] 3 4 ... 25