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Messages - neuroanatomist

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Software & Accessories / Re: Automatic Microfocus adjustment software
« on: January 09, 2012, 03:22:10 PM »
for a zoom lens ie 24-105 L IS,   it gives you 3 values at 3 different focal lengths, does the camera store all of them or do you have to choose one of them?

You have to choose one. I'd bias the choice toward the long end of the zoom, since that's where DoF will be thinnest and thus AF errors more obvious.

FWIW, the 1D X will store two AFMA values for a zoom lens.  I don't know what it will do with them, i.e. change from one to the other halfway through the zoom range, or progressively change from one to the other over the range.

PowerShot Cameras / Re: Canon PowerShot G1 X Announced
« on: January 09, 2012, 02:52:53 PM »
Next question is how much bigger is it to the G12.

0.2" taller, 0.2" wider, 0.6" thicker.

If it grows by those dimensions again, it'll be the size of a Rebel. Heck, as it is the G1X weighs the same as the T3.

EOS Bodies / Re: 1D X Limitations Fixable?
« on: January 09, 2012, 02:29:54 PM »
I certainly hope that Canon will fix the "Achilles heel" for what otherwise appears to be a stellar camera. Autofocusing at f:8, even if only in the center spot, has been a given for 1D series users for a decade now.  Taking it back seems such a step in the wrong direction and gives us one less reason why these bodies are our first choice.

Well, overall I think it is a stellar camera. I agree with the previous comment that the lack of f/8 AF is a real issue for only a very small percentage users.  (Dare I say it, perhaps more people are complaining about this issue online than there are current 1-series users who would be directly impacted?) 

As discussed, they may not be able to 'fix it' for technical reasons.  Consider - previous 1-series have a center point that's an f/4 line crossed with an f/8 line. The 1D X will have a dual f/2.8 and f/5.6 cross.  It may be that Canon's lines differ from Nikon's - I know Canon uses 48-bit lines of all the same length, but different separation relative to the baseline (wider spacing for f/2.8 than f/5.6).  The exception to that is the previous 1-series, where the lines for the center AF point are closer together (f/4 and f/8 spacing), but the lines are shorter so the higher pixel density regains the accuracy lost to the shorter baseline. That may not have been possible in the new sensor with its higher level of complexity.  I don't know what the sensor lines for Nikon are like, but it may be that they have been using higher density AF Lines all along. Thus, Nikon's f/5.6 points might be more accurate than Canon's f/5.6 points, and that greater accuracy might allow them to work better at apertures narrower than f/5.6. 

It may also depend on exactly why Canon chose to eliminate the f/8 capability.  If it was for marketing rather than technical reasons, they may be setting the stage for a future pro-level crop body, such as a 14-16 MP APS-C, with substantial IQ improvements, where they'll bring back an f/8 capability, expanded to multiple points.

Software & Accessories / Re: Automatic Microfocus adjustment software
« on: January 09, 2012, 12:09:34 PM »
The larger adjustment range is a promised feature at some time in the future.

"And the following tests coming shortly after release:  

Out of range testing - take the AF Micro adjustment value outside of the normal +/-20 range for problematic lenses.

Yes, I read that, too - that was the point of my question. When I read that, it suggests to me that the testing will be capable of going beyond the normal range, but it does not indicate that it will be possible to actually set an in-camera AFMA outside the normal range.  Do you think the latter would be possible without altering the firmware? 

Looking at the plots you posted, I'd bet the shape of the curves would be pretty similar for a given lens, or perhaps class of lenses. So, given sufficient data on those lenses, if a curve is 'trending up but starting to approach a peak' between, say, +14 and +20, but hasn't peaked yet, the software will extrapolate the curve and report that you'd need a +23 adjustment, even though it didn't test +23. Alternatively, since the software can measure the time between initiating focus and focus lock each time, and also the direction, it could apply a 'manual focus' adjustment equal to one AFMA unit for values beyond 20, and measure the sharpness at those expanded settings, providing real data for the plots.

But, I think the only way an out-of-range adjustment could actually be applied and used when the camera isn't connected to FoCal would be a ML-type firmware hack.  I'd be very interested to hear other opinions, or examples of other custom functions having their available parameters changed externally.

.... If I understood neuro's tech posts correctly, the DOF will be more shallow on FF for the same subject distance and framing.
I thought for the same subject distance, the Crop has more OOF blur, but for the same framing the FF has more OOF blur...

Yes but what if you have both the same subject distance and the same framing, i.e. only a different focal length?
I will defer that one to Neuro  ;D

If you have the same distance and same framing, but different focal length, the FF will have shallower DoF for the same aperture, because it will need a longer focal length. Example - 85mm f/2 on APS-C at the same distance will frame like 135mm f/2 on FF.

K-amps, you're correct that if you keep everything the same but the sensor - same aperture, same distance, same focal length, the crop sensor will actually have shallower DoF.  But we don't usually care much about that because it's a different picture. So, if you're taking a head shot on FF, you could get more OOF blur (shallower DoF) by switching to a crop body and shooting with the same lens at the same distance - but then you'd have a shot of just the subject's eyes and nose (so, you'd move back to frame the head, and then your DoF would be deeper than with FF).

Lenses / Re: 24mm 1.4L ii vs 35mm 1.4L vs 50mm 1.2L
« on: January 09, 2012, 11:41:09 AM »
I guess I should clarify a bit more Neuro.  I would have expected your explaination if all the test shots at f/1.8 were a little OOF than the f/1.2 shots.  In all but this one instance, the f/1.2 shot was sharper than the f/1.8 shot.  I also have to confess, I was looking at these images at 200% and I'm probably a closet pixel peeper.

Apologies, but I don't understand your clarification. Are you saying that in general, f/1.2 was sharper than f/1.8, or in one specific shot, f/1.2 was sharper, but the rest of the time, f/1.8 was sharper? 

What I'm saying is that with correct focus, f/1.8 will always be sharper than f/1.2, that's just basic optics - you stop down from wide open and the lens gets sharper.  MTF tests and/or ISO 12233 test shots, which when properly done are perfectly focused (either with 10x Live View, or better yet by focus bracketing and picking the best shot post hoc).  But, what I'm also saying is that if you are using AF for your shots, f/1.2 will usually be sharper than f/1.8, because the f/1.2 shots will be correctly focused, while f/1.8 will be back focused because of the focus shift (focus shift does not apply wide open).  However, that also assumes the lens is properly calibrated on your body - for example, if it actually front-focuses at f/1.2, then the focus shift at f/1.8 may result in correct focus (two wrongs making a right, so to speak).

PowerShot Cameras / Re: Canon PowerShot G1 X Announced
« on: January 09, 2012, 11:17:51 AM »
Extensive accessories

But apparently no wide or tele adapters.  One 'accessory' they provide for free is the 'cap keeper'.  The G1X has an actual lens cap - no auto-retracting cover. Canon helpfully includes an attachment string, so the cap can dangle around while you shoot (hmmm, what's that loud click-click-click on that video I just shot?).

Despite having a physical cap, there are no filter threads on the lens. You can buy an optional adapter to hold a filter (58mm), or a lens hood.  Note - that's OR - you can't use both a filter and a hood together.

PowerShot Cameras / Re: *UPDATE 3* Canon PowerShot G1X Revealed
« on: January 09, 2012, 11:09:01 AM »
Considering how much bigger the sensor is I think we'll be ok. The pic from dpreview gives you a better idea of how giant that thing is. And considering about the amazing amount of detail everyone goes in about how important pixel / sensor size is whenever that subject comes up I think we have a lot to be happy about with Canon in their general direction.

Well, yes, sensor size is important. But even more than hammering on 'bigger sensors are better', we hammer on 'glass before body'. A good lens on a smaller sensor (e.g. a 70-200 L-series on APS-C) will far outperform a poor lens on a larger sensor (e.g. the cheap 75-300mm III on a 5DII).  With a sensor nearly the size of APS-C, but a lens smaller than the 18-55mm kit lens, I do have some concerns about IQ. Not that the 18-55mm is horrible, but compared to lenses like the 17-55mm or 15-85mm, it's not in the same class, and a bigger sensor exposes more flaws in a lens.

When out and about with a P&S for emergency photographic opportunities we may not have a lot of time to set up and compose a shot.  The large DoF of the P&S means we can be quicker and still be sure the subject will be in focus.

Yep. Oh, and with the G1X, you'll have to factor in time to remove the lens cap - no auto-retracting cover. Canon helpfully includes an attachment string, so the cap can dangle around while you shoot (hmmm, what's that loud click-click-click on that video I just shot?).

PowerShot Cameras / Re: *UPDATE 3* Canon PowerShot G1X Revealed
« on: January 09, 2012, 10:38:23 AM »
Still - the big sensor makes it interesting, and justifies the price tag!

But will you buy one neuro?  You may recall my previously stated gear buying policy.

LOL. No, I don't plan to buy one.  For me, it's still too big - larger than truly pocketable (and I don't count cargo pants or coats for that), I'll just bring a dSLR. 

There's one thing that might change my mind - if the AF speed and shutter lag approach those of a dSLR, then I'd consider it.  That's one of the biggest downsides to a P&S, and one of the reasons I bring a dSLR unless I just can't.  I'm sure that someday, contrast-detect AF will get fast enough, but I don't think it's there yet.  In that regard, the bigger sensor is a disadvantage - the S100 has a fast burst rate, and because the DoF is deep, the lack of AF between shots isn't a big deal. But with a shallower DoF, a moving subject can more easily move out of the DoF.  In fact, I often set my S100 to MF and rely on the deep DoF you get even with a wide aperture to eliminate the need for (and more importantly, the time it takes to) AF. 

EDIT: one thing I just noticed - an optional 40m waterproof case.  The ISO capabilities of a large sensor might make this a great option for diving.  But then again, the combined price of the G1X and the housing will start to approach the cost of an Ikelite dSLR housing, and 28mm isn't really wide enough, and the 'extensive accessories' don't include a WA adapter.

Lenses / Re: Should I purchase the 15-85mm f/3.5-5.0?
« on: January 09, 2012, 10:10:59 AM »
I've found myself liking less and less the wide angle look for most most walk-around shots; my pictures seem better this way.

Wide and especially ultrawide shots are more challenging to compose.  If you fall into the habit of looking around at an interesting scene, then just holding up the camera and shooting a wide shot to capture what your eyes see, you're almost guaranteed to be disappointed.

Instead, try to find some interesting foreground element to highlight, or use leading lines to draw the eyes into the scene.  Here's an example of each:

EOS 5D Mark II, EF 16-35mm f/2.8L II USM @ 27mm, 1/25 s, f/2.8, ISO 3200

EOS 7D, EF-S 10-22mm f/3.5-4.5 USM @ 10mm, 0.6 s, f/14, ISO 100

PowerShot Cameras / Re: *UPDATE 3* Canon PowerShot G1X Revealed
« on: January 09, 2012, 09:42:23 AM »
It does indeed - but we also see the compromises that were made.  It's much thicker than the G12, most of that is the protruding lens. It's not f/2.5, but f/2.8 at the wide end.  Where the G12 is f/4.5 at the long end, the G1X is a narrow f/5.8.  We'll have to wait and see if other compromises were made in lens design, and how the lens quality holds up to the large sensor.

One more thing occurs to me - I did overemphasize comparisons to EF/-S lenses. Thinking back, the combination of 1/3-stop narrower at the wide end, a very narrow long end make some difference, but importantly, it's a 4:3 sensor, not 3:2, and 4:3 makes more efficient use of the image circle, so all of the lens elements can be smaller than would be inferred from a lens needed for a 3:2 sensor.

Still - the big sensor makes it interesting, and justifies the price tag!

EOS Bodies / Re: 1D X Limitations Fixable?
« on: January 09, 2012, 09:21:06 AM »
an f/5.6 lens with a 2x teleconverter would. Not being able to use AF at that point would rather suck.

Actually, an f/5.6 lens with a 1.4x or an f/4 lens with a 2x would be f/8.  It's not as bad as it sounds for most people - if you put a TC on an 'affordable' long lens (2x on 300/4 IS, 1.4x on 400/5.6 or 100-400), the IQ takes a substantial hit, resulting in a pretty soft image.  Those most affected are people using supertele lenses, e.g. the 500/4 or 600/4 + 2x, or the 800/5.6 + 1.4x (I've run into birders with the latter).  Most people doing that are shooting 1D-series bodies, so they're taking a double hit - loss of 1.3x crop and loss of f/8 AF.

Lenses / Re: 24mm 1.4L ii vs 35mm 1.4L vs 50mm 1.2L
« on: January 08, 2012, 10:15:48 PM »
I don't get OOF shots unless I've had a brain fart.  Just this afternoon, I was taking a few shots of one of our cats with fill flash at f/1.2 and f/1.8.  When I was comparing the two shots in LR, I was surprised that the f/1.2 was sharper.  I understand that the 50L can be softer at f/1.2, but based on my testing, technique may have something to do with it.

It's a poor craftsman who blames his tools.  :P  Except, in this case, it's the tool's fault. If you look closely, you'll find that your f/1.8 OOF shots are a bit back-focused. The 50L exhibits noticeable focus shift - as you stop down, the focal plane changes. So, since lenses are focused wide open, if you shoot wide open, no problem. By f/4 or so (depending on subject distance), the DoF is getting deep enough to mask the effect. But, between f/1.3 and ~f/4, the focus shift results in back-focusing.

There are some workarounds - shoot wide open or narrower than f/4, MF with the DoF Preview button pressed and a precision focusing screen (problematic on the 7D since you can't easily switch screens), Live View, focus on something a little in front of where you need to, or tweak the focus manually after AF (which takes a lot of practice to become proficient).

Enjoy the lens!

EOS Bodies / Re: 1D Mk II dioptric adjustment method
« on: January 08, 2012, 07:45:30 PM »
Paul, I think OP's point was there is a slight difference in what you pick as an adjustment method - moving dial until AF points are clear vs. until the VF info display is clear. 

You've provided a third option - my question for that option is how you are sure the high- contrast subject out in the field is truly in focus. Are you simply trusting the AF?

EOS Bodies / Re: 1D Mk II dioptric adjustment method
« on: January 08, 2012, 07:31:12 PM »
The AF point marks and spot circle are etched on the superimpose screen that's right up against the focusing screen and as such make the best reference to set the diopter.

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