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Messages - epsiloneri

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331
Thanks for the link. The one thing I take away from that comparison is that you don't have to understand optics in all its details to be an awesome photographer. I guess in the same way as you can be an excellent driver without knowing the intricacies of how your car works. But we already knew that.

332
EOS Bodies / Re: *UPDATE* 1Ds Mark IV Feature
« on: October 20, 2010, 03:57:52 PM »
If you bin on chip you cut the readout noise out of the problem.

If readout noise is indeed significant, then yes, it would be advantageous. But is it? Usually readout noise becomes important for very low S/N in an image, i.e. underexposed parts such as deep shadows, and limits the dynamic range available. I wonder at what exposure level the readout noise becomes comparable to the photon noise.

333
Lenses / Re: Is the EF-S 35mm f/1.8 coming?
« on: October 20, 2010, 03:34:11 PM »
Therefore, I don't expect to see new EF-S primes coming out - they'll release consumer-level zooms for the Rebel owners, and EF (mostly L) lenses for the 'everyone else' group.

Sadly, I think you're right. I hope you're wrong, though.

334
EOS Bodies / Re: decisions decisions!
« on: October 19, 2010, 08:07:33 PM »
I had the same decision to make when my little girl destroyed my 400D.

And, the build quality is definitely better on the 7D compared to the 400D  ;)

335
EOS Bodies / Re: decisions decisions!
« on: October 19, 2010, 08:04:25 PM »
But, as i said - in terms of the 40d i was satisfied with most things bar its ISO performance in low light, i found even at 800/1600 noise was a problem shooting low light, night time exposures, indoors without flash and concerts etc. i do shoot a wide variety of things, but night time, and concerts are two of my favourite subjects, as is shooting with natural light in general which often requires good iso performance.

If you shoot low light, then I definitely recommend a FF camera - not necessarily Canon. 5D2 (and 50D) has a problem with pattern noise that limits its dynamic range, which can be limiting in some cases. 7D is much better in that respect, and the hope is that Canon will have fixed it also for the 5D3 (I don't know about the 60D).

The main reason for going FF is the lens advantage. You will find an excellent EF 85/1.8 for little money, but there is no competing equivalent EF-S 50/1.1 for APS-C (nor will there probably be). Same thing goes for the whole focal range.

336
EOS Bodies / Re: *UPDATE* 1Ds Mark IV Feature
« on: October 19, 2010, 07:47:11 PM »
Actually noise performance could be improved non-trivially in a binned environment.  Basically you are working with 4 times the number of data sources, so the random variance because 1/4 as strong.  I'm definitely not using the right terminology right now (you'll have to forgive me, it's been a *very* long day at the office), but I did want to respond with a general direction of what I'm thinking.  I'll respond later tonight or tomorrow in more detail if you would like, but long story made very short, you have 4x the signal to 1x the noise in a 4:1 (2x2) bin.  That is significant.

I understand that binning increases the signal/noise per pixel, but my point is that the binning doesn't need to be in camera. You can later bin the full resolution raw image in software with the same noise improvement. But perhaps you were referring to some other advantage?

(the S/N will improve 2x for 2x2 binning: the signal increases 4x but the noise only 2x because of the tendency of random noise to "cancel out" when you add it up - that's why adding up 4 noisy pixels only gives twice the noise as a single pixel)

337
Lenses / Re: Is the EF-S 35mm f/1.8 coming?
« on: October 19, 2010, 07:36:41 PM »
What is the point to make new EF-S lens??? Would be much better to renew EF 35mm f/2

The point is that EF lenses are wasteful for crop cameras. EF-S can be made much smaller and cheaper. Just think of the G12 with its 28-140/2.8-4.5 lens and think how big it would be if the lens had to be EF compatible. More extreme, but same thing.

Currently, the only EF-S prime is the EF-S 60/2.8 macro. I'm sure high-quality EF-S primes in a small form factor would find its audience. Most dSLRs are not FF anyway.

338
EOS Bodies / Re: *UPDATE* 1Ds Mark IV Feature
« on: October 19, 2010, 07:04:01 PM »
This gives them room to improve the 5D line and a *key* feature to differentiate the 1Ds. Pixel binning would be huge is potential advantage for low-light and/or extreme high quality work.

Why is that? The only advantage I see with in-camera binning is size of files/speed (which is nice, but I don't see the huge potential). One might also save some readout noise, but I doubt that's significant in most situations.

339
Lenses / Re: Sigma 85 f/1.4 EX DG Available Soon
« on: October 17, 2010, 05:33:12 AM »
Because all FF lenses perform better on crop bodies which take advantage of the sweet spot

That's true, but the FF optical performance of the sigma is not much in question. Its border resolution is as good or better than the Canon EF 50mm f/1.2 USM L (which itself is not very good in the border resolution department; see photozone.de, or the review by dpreview.com). The problem with the sigma is its AF. And I cannot see how AF issues would be less on a crop body.

For equivalent framing to use of the lens on FF, the depth of field on the crop body would be deeper.  So, f tihere are AF issues, they would be masked on a crop body by the deeper DoF.

Hehe, I think we've covered this topic before. Actually, AF issues get worse, if anything, with crop. I'm not going through the crop vs. FF lens/image equivalence thing again, but will merely give you an example that will make you immediately understand why. Imagine you have a focus error with a FF camera, such that the de-focused resolution is 1/160 of the image width (0.6%). Then the equivalent image in a crop camera, would be to crop that exact FF image with a factor 1.6x. The AF error would now be 1/100 (1%) of the image size - which is clearly worse. Resolution in terms of resolved minimum angle would of course be the same (the crop image is, after all, the central part of the same image as the FF).

340
Lenses / Re: Sigma 85 f/1.4 EX DG Available Soon
« on: October 16, 2010, 12:19:42 PM »
Reasonable in what way?  Fair? here's a quote:
These were not even close-distance shots that are typically most challenging for shallow DOF lenses.

For my copy, AF works better for close distance shots, strangely enough. The AF actually only misbehave on distance shots (> a few meters).

I think that this lens would be better suited to a crop frame camera, I have sold the Canon f1.4 50mm in the hope of a replacement which I think will be a vain one as Canon haven't released a  non L FF prime in too many years.

Why do would the Sigma 50mm/1.4 be better on a crop?


341
Lenses / Re: Sigma 85 f/1.4 EX DG Available Soon
« on: October 15, 2010, 07:22:03 PM »
Is the Sigma 50 1.4 really all that good?

I love my sigma 50mm/1.4 optically. And the bokeh is superb. Unfortunately I've found the AF to be unreliable at distances larger than a few meters. Unless the AF has been fixed in later versions (I have an early copy), I would not recommend this lens.

Unfortunately, the sigmas I've tried have not been as reliable with AF as canons (in general). Unfortunately, because their lenses are often optically very good.

342
Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 13, 2010, 02:42:13 PM »
So, I'll take a few steps forward to get that nice tight framing again, and that decreased distance-to-subject translates to a shallower DoF - by a factor of 1.6x.

Yes, but the perspective will have all changed, so it's not equivalent. I think we both agree that, in contrast, the imaged formed by a 50mm/2.8 lens on a FF sensor is actually equivalent to the image formed by a 31.25mm/1.75 lens on a 1.6x APS-C sensor. Actually equivalent (identical!), in terms field of view, photon collection rate per solid angle, depth of field. No difference.

343
Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 13, 2010, 02:30:59 PM »
Photozones test of the 24 - 105mm f/4 IS on FF wasn't what I wanted to see, it has problems with edge softness vignetting, distortion, and its minimum focus distance and magnification leave a lot to be desired.  It's useless for close up work, the 17 - 55mm is much closer to the 24 - 70mm here.

As I already wrote, according to the photozone tests themselves, 24-105mm/4.0L on 5D2 is at least as good as 17-55mm/2.8 on 7D, at least if we're talking IQ (7D has other advantages). I confirmed it with my own tests. In other words, the 17-55mm/2.8 on 7D is just as useless as 24-105mm/4.0L on 5D2.

f/2.8 on APS-C gives about the same viewfinder brightness as f/4.5 on FF. Why is that? Because in order to view the full field of view in the same solid angle, the FF viewfinder needs to compress the image (almost) 1.6x more than the APS-C viewfinder -> increasing the surface brightness. This is easy to test yourself: mount the 17-55/f2.8 on a 7D and the 24-105/4L on a 5D2. Which viewfinder is brightest? They're about the same (the 5D2 has a slightly larger apparent field in the viewfinder, but it's compensated by the lens being 4.0 instead of 4.5). If you don't believe me try it! (Of course, your 24-70mm/2.8L lens will be much brighter on the 5D2.)

344
Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 13, 2010, 05:23:37 AM »
So you don't agree that 50mm/2.8 on a FF is identical to 31.25mm/1.75 on 1.6 APS-C? Or is it something else?

Yes I don't agree with that, f/2.8 is f/2.8 regardless of the crop factor

Ok, good, then I understand. You are right, that for the same lens the aperture doesn't change when you go from FF to crop. That would be weird. But now think of two different lenses that both share the same entrance pupil - say 18mm in both cases - but where the focal length is different, namely 50mm in one case and 31.25mm in the other. Then the image on a FF with the 50mm lens would be identical to the image of the 31.25mm on the 1.6x APS-C. And, also note, since the entrance pupil is the same, the f/#-number changes: 50/18 = 2.8 while 30/18 = 1.75. Which is what I stated in the quote above.

345
EOS Bodies / Re: Lenses in 2011 [CR2]
« on: October 13, 2010, 05:12:36 AM »
I don't know what's going on, but surprisingly The Digital Picture has the TS-E 24mm just trouncing the EF 24mm f/1.4

I think it's because the the EF 24/1.4L II is strongly optimised for wide open 1.4 performance, which is very different from 3.5. It is reasonable that photographers would use the 24/1.4 wide open a lot of the time, since it's the defining feature of the lens. You may also note that the EF 24/1.4L II @ 2.8 is sharper than the EF 16-35/2.8 II @ 2.8, but the latter is sharper when both are @ 5.6.

I think it's the same optimisation that's been done for the EF 50mm/1.2L, where its much cheaper brethren beats it in terms of sharpness for smaller apertures.

So, in conclusion, if you don't care too much after low-light performance (or very shallow DOF) but are more interested in having the ultimate sharp lens (as commonly the case in landscape photography), the slower lenses might be better for you. They're also often cheaper (though not the TS-E 24/3.5L II, obviously). The only caveat is that almost all of the non-L primes are of old design, and as we know from the recent L-updates (during the last couple of years) that performance tends to improve a lot with an update.

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