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04-07-2013, 01:09 PM   #1
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A question for the MTF guys.

Has any of you ever done a comparison of MTF numbers comparing hand held, tripod with hand shutter and tripod with 2 second delay (and no shake reduction? )

After reading the lengths the guys at DPReveiew went through to get 4000 lw/ph out of a D800, it made me wonder, what like field results would be. And then of course the useful corollary, is it worth paying for high end glass in everyday photography?

Obviously if even with shake reduction on motion blur, and slightly innacurate focus are both going to cause image degradation, you have to wonder if a not so sharp lens might do just as well as the sharpest, if you're shooting hand held, or not damping camera vibration.

It's fun seeing lab results, but what happens in the field?

Anyone got anything?

04-07-2013, 02:55 PM   #2
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It's all about technique, I think, with thanks to Heie. That said, if you get significantly different results on (a stabilized with enough weight) tripod, try working on your 'shooting form'
04-07-2013, 07:14 PM - 1 Like   #3
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I think the question is more "Why did they do that?" I am not sure what they thought they might prove because anything of real interest was beyond the limits of their ability to measure it.

Theoretically, the Nyquist limit for a given sensor in line widths per picture height is the same as the number of pixels in vertical rows on the sensor. I apologise if that is not quite how the boffins would express it. But the D800 full frame sensor (24X36 mm) has a height of 4912 pixels. Acrosss 24 mm, that is about 205 pixels per mm. The dpreview test concluded that the D800 was good for about 3200 lw/ph in jpeg mode which, they said, was about what they would expect for practical purposes For the D800e they were approaching 4000 lw/ph but with "more obvious false colour (the result of having no AA filter). We don't know how high the lw/ph would have gone in RAW because they could not measure past 4000 lw/ph.

Now look at the K-01. The APS-C sensor (15.7x24 mm) has a height of 3264 pixels. Across 15.7 mm, that is about 208 pixels per mm.All things considered (I am working fairly rough here) there is probably no significant difference in pixel size between the D800 sensor and the K-01 sensor. the dpreview test of the K-01 found it was good for about 2400 lw/ph in jpeg (although to my eyes, it looks closer to 2600 lw/ph). The dpreview test also found that the K-01 was good for 3000+ lw/ph in RAW That is, it was approaching the Nyquist limit in which lw/ph is the same as pixel height.

Pixel for pixel, the K-01 would appear to be outperforming the D800 in the jpeg stakes, but the K-01 has a weak AA filter. It falls between the D800 and D800e (with no AA filter) in resolution on the similar pixel size.

So ... the steadier the camera, the less shake the sharper the image should be. But MTF is a measure of light transmission. The lens has an MTF, the AA filter (and any other filter in front of or behind the lens) has an MTF, and the sensor itself has an MTF. These do not change because of how steady the camera is. But camera shake can mean that the image produced is less than the MTF potential. But you already know that. I just can't understand why dpreview went to those lengths for something that knew would be beyond their measuring ability anyway.
04-08-2013, 05:46 AM   #4
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MTF is measured in LW/PH. So I think what I'm asking is - once you get out of the lab, what kind of MLW/PH are you getting in various real world situations. I once saw a comparison of various 35 mm images taken at different settings, with and without tripods. The difference was more than the difference between a good and bad lens if you blew the image up to 11x14. Or to put it another way a bad lens on a tripod is better than a good lens hand held.

I'm sure the same is still true. I'm just wondering if anyone has actually used lW/PH to verify that.


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