Shallow DOF with fast lenses: is this really an issue?

Started Feb 21, 2013 | Discussions thread
Draek Senior Member • Posts: 2,028
Re: Shallow DOF with fast lenses: is this really an issue?

My apologies for the late reply; I meant to provide evidence of my statements, but after failing to find my old tripod the matter disappeared from my mind.

Still, here's the problem with your images: they're still both within the operational limits of the camera, which is why they look so similar---as they ought, given basic physics. The problems, rather, begin when you start pushing ´╗┐beyond´╗┐ those limits, for instance by setting the compact to ISO400 or 800, as is typical for low light levels; you ain't going to shoot anything alive with a 0.8s exposure. This is just a test made in haste, without a tripod or even equivalent lens to make them a closer match, but here's a pair of quick photos taken, respectively, with my 1/1.7" Samsung EX1 at ISO800 72mm-equivalent f/2.4 and my Sony A390 at ISO3200 (pushed +1 on LR) 75mm-equivalent f/7.1, both with the latest CCD sensors Sony made for each format before switching to CMOS. 100% crops, Custom WB measured off the notebook paper that served as background, all other settings on default (except for the +1 push on the SLR file).

ISO800 on a 1/1.7" (4.7x crop) compact...

...against ISO6400 (equiv) on an APS-C (1.5x crop) SLR.

Oh, and I must note as well, that the difference in focal length was larger than expected; the EX1 shot was considerably wider than the A390's, even though (theoretically) it was a match between 72mm and 75mm---probably the difference in aspect ratio, though it would've favored the Sony in any case. Oh, and there's a 1/6th of a stop difference in exposure as well, since the A390 measures in thirds while the EX1 does so in halves.

Still, I'm planning to repeat the test in a more controlled manner as soon as I find my damned tripod, likely with the 18-55 instead of the 50mm and matching horizontal FOV rather than focal length and perhaps with a better subject than my garlic supplements but I don't think things would change significantly---the inaccuracies in theory at least would've served to hinder the EX1, not help it, and it still came out as the clear winner.

 Draek's gear list:Draek's gear list
Fujifilm FinePix F70EXR Samsung TL500 Canon PowerShot A1200 Sony Alpha DSLR-A390
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