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

Started Feb 21, 2013 | Discussions thread
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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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