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next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL
#12
[quote name='Brightcolours' timestamp='1300400414' post='6916']

The bar's height have a direct relation to the maximum achievable resolving power of the camera used. You do not have to take my word for it, but you really can get a really good impression of a lens' sharpness just by comparing the bar height in relation to the vertical axis, without looking at the measured numbers.



Two examples:

Pentax K10 with Tamron 90mm f2.8 DimMacro:

[Image: mtf.gif]

Canon EOS 350D with same Tamron 90mm f2.8 Di macro:

[Image: mtf.gif]



Canon EOS 350D with Canon EF 100mm f2.8 USM macro:

[Image: mtf.gif]

Canon EOS 50D with Canon EF 100mm f2.8 USM macro:

[Image: mtf.png]



As you can see, the bars show a very similar height both for the 10mp Pentax K10 and the 8mp Canon EOS 350D, both with a Tamron 90mm.

And same with the bars for the 8mp 350D and 15mp EOS 50D, both with a Canon 100mm macro.



The vertical axis is important, it shows the maximum achievable resolution for the sensor. Since for each camera the scale on the vertical bar is different, you can compare results from the K10 tests and the K5 test. Only when a lens starts to resolve about half the maximum achievable reults, you will start to see real differences between sensors with different resolutions.

[/quote]



But this is exactly what I was pointing at. The same lens (if we assume that there were no lens sample variations) mounted on the 10 Mp Pentax camera achieved 2180 pixels (per the image hight) resolution, while mounted on the 8 Mp Canon camera it achieved only 1999 pixels. For sure, poor lenses will show more less the same resolution regardless of the sensor resolution. But a high quality lens will be much more limited by the sensor resolution. And while the sensor requires use of the AA filter (which is still the case even of contemporary 18 Mp sensors), it clearly means that their spacial resolution is still below the Nyquest frequency. Yes, once the future sensors have maybe more than 20 Mp, then their resolving power will not limit even the best lens. How much pixels such sensors would need? I remember, that best lenses from the film era could not resolve more than 100 lp/mm, so let's use that number, though today's lenses, optimized for the APS-C size sensors could have (much) higher resolution. To satisfy the sampling theory, the sensor without a need for the AA filter should have 2 x 100 x 16 (the APS-C sensor hight) pixels in the vertical direction, which is more than 15 Mp for the entire sensor. So, the same lens tested on a camera with a 10 Mp and 16 Mp sensor will show very different resolution.
  


Messages In This Thread
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by AlbertoM - 03-15-2011, 06:19 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-17-2011, 02:21 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-17-2011, 09:56 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-18-2011, 12:27 AM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-20-2011, 01:20 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-20-2011, 06:46 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by flektogon - 03-20-2011, 08:37 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by arvydas - 03-20-2011, 10:45 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 03-22-2011, 06:07 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 03-22-2011, 08:17 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 03-22-2011, 09:41 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 03-22-2011, 09:45 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by froeschle - 04-20-2011, 01:30 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 04-20-2011, 02:09 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 04-20-2011, 05:21 PM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 04-22-2011, 06:10 AM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 04-22-2011, 06:47 AM
next PZ lens test report: Pentax SMC DA 35mm f/2.4 AL - by Christos - 04-22-2011, 07:31 AM

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