Messages

196

Software & Accessories / Re: Automatic Microfocus adjustment software

« on: January 21, 2012, 09:25:33 PM »

Neuroanatomist, you say: "I wonder if this is due to the thinner DoF with the 7D (the distances are the same as with the 5DII, so the shot/framing is different, but under those conditions the APS-C sensor delivers shallower DoF)."

Is that due to the smaller pixel size on the 7D? We always say that for the same FOV the DOF will be shallower on a full-frame sensor b/c you'll be using a longer focal length lens. But for your setup, using the same focal length, if I remember correctly, a higher spatial sampling rate (smaller pixel size) would actually lead to smaller DOF... though I wonder about the magnitude of this effect!

Also, I began doing these sorts of thorough tests with a LensAlign and image quantification software (moving to Matlab soon) to determine the best MA for my 85mm primes. I found that judging the results by eye introduced too much subjectivity. Though I haven't completed my tests, it would appear that my Sigma 85/1.4 doesn't even show a clear trend with the microadjustment settings. Meaning it jumps around randomly, rather than showing a clear trend from front-focusing to back-focusing. Not as much so with my Canon 85/1.2. I wonder if this is due to low precision of focus with the Sigma lens.

Therefore, I'm repeating my focus tests 20 times for each MA setting: 10 times throwing off the focus slightly forward, & 10 times throwing it off slightly backward, before refocusing. I have yet to quantitate and graph these results.

The nice thing is, one can also quantitate DOF using this sort of analysis with the LensAlign. Preliminarily, I've shown that the Sigma at f/1.4 has an equivalent DOF as the Canon at f/1.6 (for the same magnification of subject). Interesting.

BTW I'm using a Canon 5D Mark II. Just having a heck of a hard time determining optimal MA setting with the 85mm primes. No problem with any of my other lenses (35/1.4, 70-200 f/2.8, etc.).

Would definitely be interested in giving FoCal a try.

197

Canon General / Re: Canon Files a Patent for a Bunch of Lenses.

« on: December 16, 2011, 04:03:14 PM »

The 85mm f/1.2 II lens is in dire need of a 9-blade aperture.

Sigma's 85/1.4 creates much more pleasing OOF highlights b/c its 9-blade aperture is much more circular than Canon's.

198

Canon General / Re: Canon Files a Patent for a Bunch of Lenses.

« on: December 16, 2011, 03:59:53 PM »

The 24/1.4 II should be a top priority for Canon b/c it has -3 stops of vignetting at the corners/edges. 3 stops. That's like the edges of your image effectively being shot at ISO 6400 rather than ISO 800 by the time you've corrected for vignetting in software. In comparison, the Nikon 24/1.4 has only 1.5 stops of vignetting at the corners/edges. Just look at the comparison btwn the two:

http://the-digital-picture.com/Reviews/Lens-Vignetting-Test-Results.aspx?FLI=0&API=0&FLIComp=0&APIComp=0&Lens=480&Camera=453&LensComp=690

Yeah a lot of the time for people photos I don't care about vignetting but the 24/1.4 has a specific use case: environmental portraits. And in such portraits where you want to separate the subject from the background (landscape), using 1.4 is beneficial. And in such cases (landscapes) one typically doesn't want vignetting.

The 35/1.4 needs an update? Why? Perhaps for weather sealing but I can't imagine any other possible reason... the lens is perfection minus my gripes about a 72mm filter ring & the lack of weather protection.

Rishi

199

Lenses / Re: Canon 85mm 1.2LII vs Sigma 85mm 1.4

« on: December 07, 2011, 07:42:15 PM »

Yeah competition is good & I hope Sigma's 9-blade much-more-circular aperture forces Canon to rethink their 85/1.2 II. This is one aspect in which the Sigma lens is not only as good as, but, better than the Canon 85L. As one of the previously posted reviews itself states.

200

Lenses / Re: Canon 85mm 1.2LII vs Sigma 85mm 1.4

« on: December 07, 2011, 12:34:08 AM »

Yeah anyone that can manually focus with an 85mm lens < f/2.0 & still get critical focus with hit rates >50% is a magician to me Unless you have stationary subjects & have a lot of time... in which case I might just use live-view.

A loupe on the viewfinder might be nice...

I guess since focusing & recomposing will always lead to back-focus one could try & compensate by firing off a number of shots while slowly leaning backward (I think I got that right?). Seems a little funny to me though.

201

Lenses / Re: Canon 85mm 1.2LII vs Sigma 85mm 1.4

« on: December 06, 2011, 04:15:29 PM »

Yeah my Sigma also needed a +3 microadjustment but, then again, so did my Canon 35L.

After that, center point focus was dead on. It consistently hit my test chart at a 45º angle at the right spot.

But when using the right-most AF point on my 5DMkII, focus was rather erratic. Dead-on, back-focused, front-focused, you name it.

However, same performance with my Canon 35L, so I doubt the Sigma lens is at fault here and, rather, it's the low precision of the outer AF points on the 5DMkII that render it nearly impossible to nail focus with such shallow DOF.

202

Lenses / Re: Canon 85mm 1.2LII vs Sigma 85mm 1.4

« on: December 06, 2011, 12:39:13 AM »

One thing I like better about the Sigma 85/1.4 lens is that its aperture stays circular all the way to f/2, & almost circular all the way to f/2.8.

The Canon 85/1.2 II is already non-circular by f/1.6 & pretty offensive (to my eye) by f/1.8. OOF highlights just don't look very good anymore as they have distinct shape to them.

Sigma has 9 aperture blades; Canon has 8. I'm surprised this isn't mentioned more often.

In my side-by-side tests, though, it appeared to me that at any given f-stop, the Canon lens had a wider actual opening than the Sigma (looking thru the front element). This could explain the slightly underexposed images from the Sigma as well as the lower amounts of background blur of the Sigma as opposed to the Canon.

203

EOS Bodies / Re: 5D Mark III Information [CR1]

« on: December 03, 2011, 02:59:02 PM »

The only reason I can see a landscape photographer needing a 1D series (preferably full frame) camera is for its weather sealing.

Otherwise, it's just overkill. It weighs more than the 5D series & no landscape photographer should need better AF (especially w/ the advent of Live View).

More megapixels are certainly nice for lanscapes. I would probably even take more MP over higher DR for my landscapes, b/c DR can be well controlled w/ polarizers, graduated ND filters, & HDR. IMHO, a tripod is irreplaceable for landscape photography, no matter how good the high ISO performance. Landscapes/large prints just look better at the lowest ISO possible.

The point is: if you're a landscape photog, the 5D II is more than ample (just keep one of these rainsleeves handy: http://tinyurl.com/42wjd6n). You don't *need* Canon to release a new camera to take better landscape photos, which I would argue is *not* the case for wedding/portrait photographers who seriously *need* a better full-frame body that can actually focus accurately with <f/2.8 lenses for non-centered compositions. I suppose for that purpose the 1Ds III suffices, but, man that's old tech.

204

EOS Bodies / Re: 5D Mark III Information [CR1]

« on: December 01, 2011, 03:52:43 PM »

" Canon zoom lenses can only resolve 10-18 megapixels at their sweet spot a kit lens generally resolves 10 and an L lens or some high end non-L lenes resolves 16.5-18. Many Canon prime lenses also only resolve 18 megapixels."

Where are you getting these numbers?

As I understand it, the resolving power of a system is roughly:

1/R(system) = 1/R(sensor) + 1/R(lens)

Hence, increasing the resolution of the sensor without increasing the resolving power of the lens will typically still lead to an increase in resolution of the system until you've reached the point where the resolving power of the lens is severely limiting. If one does a simple plot of this equation (see below), that ends up being when the resolution of one component is an order of magnitude greater than the resolution of the other component. At this point, increasing the resolving power of the higher resolution component leads to severely diminishing returns. See plot below:



So what I'm saying is I seriously doubt Canon's lenses resolve anywhere near 10-fold less than their sensors... which means resolution increases in sensors even without new glass will still lead to increases in MTF.

I hope people remember that just b/c a pixel looks soft on a higher resolution sensor doesn't mean that the increased sampling resolution is useless or detrimental. A higher resolution sensor will always, barring other unforeseen variables, produce at least as sharp as an image as a lower resolution sensor once you've appropriately scaled both images to the same size.

That being said, I'm more in favor of higher dynamic range sensors & I'm hoping that the tradeoff will be worthwhile in the 1Dx.
Rishi

205

EOS Bodies / Re: *UPDATED* Big Megapixel Camera Next Week.

« on: August 19, 2011, 01:07:38 AM »

In the past 3yrs of shooting digital, I've had one SD card fail completely, & one CompactFlash card start to fail when it gets closer to capacity. And I don't shoot that much. That scares me for Engagement/Wedding shoots. Mirrored slots would be extremely welcome.

206

EOS Bodies / Re: *UPDATED* Big Megapixel Camera Next Week.

« on: August 18, 2011, 07:48:36 PM »

I highly doubt they will put Dual Memory slots on the 5D3. That's a feature that will be for the 1D. If they started doing stuff like that, people would have no reason to buy a 1D at all.

And yet the Nikon puts dual card slots even in the lower end D7000...

207

EOS Bodies / Re: 1Ds Mark IV & 24-70 II in 2 Weeks?

« on: August 17, 2011, 06:34:21 PM »

Keep in mind that IS is extremely useful for hand-held video. So, though I don't find it necessary in most scenarios when shooting photos with my 24-70, I'd love it for shooting video.

I'd like IS even more on lighter lenses like the 85/1.8 or the Sigma 85/1.4. Those lenses have a long enough focal length to amplify hand motions & are light enough to not dampen them.