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FORUMS Canon Cameras, Lenses & Accessories Canon EF and EF-S Lenses 
Thread started 29 Apr 2009 (Wednesday) 19:14
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Sigma Calibration

 
ThomasOwenM
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Jun 04, 2009 21:48 |  #31

Yamaha451 wrote in post #8048190 (external link)
It would be easier to see if you posted 100% crops of each, I can't' tell a difference with those tiny pics.

I just recently got this lens also, and the focus at 1.4 is hit or miss, but mostly I believe that is from the micro thin DOF on a 5D. At 2.2 my pictures are probably the sharpest I've ever seen.

I've been trying to figure this out with my lens, but do you notice that all your pictures taken at 1.4 are a half stop underexposed compared to 1.8? Mine are all underexposed at 1.4, which does concern me...

Okay, here are some of the shots cropped, but kept at 100% of the original. I shot in small jpeg since these are test shots.

I had noticed the underexposing at 1.4. I'm leaning toward jettisoning the Sigma and using the Canon for now while I save for a 50L. I've just had trouble getting a 50 mm lens I'm in love with. Of course there is the option of sending the Siggy back again for calibration. I'll tell you, I'm drooling all over the 50D's ability to let you do your own calibration.

The shots:

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1D Mark III, Canon 50L f/1.2, Sigma 30 mm f/1.4 lens, Canon 85 mm f/1.8, 430 EX flash, ST-E2 Transmitter, Quantaray QSX 9500 tripod, Manfrotto monopod

  
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Yamaha451
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Jun 04, 2009 21:59 |  #32

My test shots looked exactly the same as yours. Mine appeard to be front focusing by 3mm or so. I posted it in the Sigma 50/1.4 forum and got this response...

Jman13 wrote in post #8016447 (external link)
Ummm...your lens looks fine. Not sure what you're complaining about. At f/1.4, it's very sharp. Your 'macro', right where you focused, is perfectly resolved...what's the problem? Take the same test chart at f/1.8 and see how you do. There is a small focus shift with this lens, and I have found that Sigma has set a properly focusing lens to front focus by a very small amount wide open near MFD, so that it focuses properly at f/1.8 and beyond, and at all other focus distances. In real world shooting, it almost never makes any difference whatsoever, and works beautifully. Also, remember that your camera focuses within a tolerance...with super-fast lenses, the best it will almost always do, is get your focus point in focus, even if you are not at the exact point...and it is. The focus here line is within the DOF, and is in focus. Is it ideally placed? Not perfectly, but it IS within the DOF, and therefore is all the AF will guarantee.

If you are expecting 100% crops at f/1.4 to be absolutely tack sharp, you are going to be disappointed with ANY 50mm lens that is currently made. Still, for 100% crops, your lens is fine at f/1.4. It shows a LOT of detail, no edge blurring, and just a small loss in contrast. Remember that 100% crops are huge enlargements. Also, on full frame, DOF is extremely shallow at f/1.4. Too shallow for most normal use close up...your thermometer photos show this...the needle hub and the 150 mark are in focus, but by the time you get to the 350 and 450 marks, it's already outside the DOF a bit.

Not sure I believe this 100%, and after a week of shooting with the lens, I think I am happy with its performance and sharpness, although I still don't like the underexposed images at 1.4.

From what I've heard, the 50L isn't worth the money compared with the sigma, but I've never used one.


-Mark-
5DII||35L|Sigma 85 1.4|24-105L| 580EX IIhttps://photography-on-the.net/forum/showthre​ad.php?t=765323

  
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ThomasOwenM
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Jun 04, 2009 22:31 as a reply to  @ Yamaha451's post |  #33

It will be a while before I get a 50L if I get one. I need to first upgrade to a 50D (or possibly a 5D). So that pushes my 50 mm upgrade back. I think my next step is to use both my 50 mm lenses in a real shoot. Thus far I've been dissatisfied with the Canon 50 1.4 from f/1.4 to 1.6 and sometimes 1.8. At 2.0 and up I've gotten great shots with it, and sometimes at 1.8. I'm not completely happy with its bokeh, but have been able to enhance it in Photoshop to my satisfaction.

I don't need f/1.2, and I rarely need 1.4 (but when I do, I do). The big praises I've heard about the 50L is its ability to AF well in low light. That would be a big deal for me. But $1300 ... ouch! However, if more of my shots were in perfect focus it might be worth it. Plus, the money I can get for both my 50s will pay for about half of that.


===============
1D Mark III, Canon 50L f/1.2, Sigma 30 mm f/1.4 lens, Canon 85 mm f/1.8, 430 EX flash, ST-E2 Transmitter, Quantaray QSX 9500 tripod, Manfrotto monopod

  
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Sigma Calibration
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