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Author Topic: Imatest resolution question - lens testing  (Read 1860 times)

JR

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Imatest resolution question - lens testing
« on: November 07, 2011, 07:57:15 AM »
This may seem like a stupid question!  When we go on www.photozone.de to look at lens test and then compare resolution charts for each lens that are based on the Imatest (LW/PH), it make sense if I only look at Canon lens say done with a FF camera.

Where I am puzzle is why when I also look at the same test for a similar Nikon lens also done on a full frame camera the LW/PH and hence the resolution always seem higher (the graphs always show a higher number).  I thought that with the 5D at 21MP and Nikon FF being at 12MP these test would almost always show Canon lens having higher resolution.

Does anyone understand the differences?  Am I comparing apple to oranges here?  Thanks in advance for your response...
1DX, 24mm f1.4L II, 35mm f1.4L, 50mm f1.2L, 85mm f1.2L II, 135mm f2L, 24-70mm f2.8L II, 70-200mm f2.8L IS II :  D800, D4, and a whole bunch of Nikon lenses

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Imatest resolution question - lens testing
« on: November 07, 2011, 07:57:15 AM »

ferdi

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Re: Imatest resolution question - lens testing
« Reply #1 on: November 07, 2011, 08:51:31 AM »
As the Photozone team explains in their FAQ, the LW/PH value is hard to compare across systems:
http://photozone.de/Reviews/lens-test-faq
Quote
LW/PH [...] [is] basically a unit for resolution (not sharpness which is a combination of contrast and resolution) limited by the max. resolution of the camera's image sensor. You shouldn't take the LW/PH value itself too seriously because it is dependent on a number of factors. The analyzing tool (Imatest) is quite vulnerable to the quality of the source material.
[...]
In the future we will probably drop the LW/PHs in favor of a school mark system which is easier to read. Refer to the reference scale on the left of the MTF charts to classify the quality.

So just look at the good/very good/ex rating.
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J. McCabe

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Re: Imatest resolution question - lens testing
« Reply #2 on: November 07, 2011, 08:55:52 AM »
This may seem like a stupid question!  When we go on www.photozone.de to look at lens test and then compare resolution charts for each lens that are based on the Imatest (LW/PH), it make sense if I only look at Canon lens say done with a FF camera.

Where I am puzzle is why when I also look at the same test for a similar Nikon lens also done on a full frame camera the LW/PH and hence the resolution always seem higher (the graphs always show a higher number).  I thought that with the 5D at 21MP and Nikon FF being at 12MP these test would almost always show Canon lens having higher resolution.

Does anyone understand the differences?  Am I comparing apple to oranges here?  Thanks in advance for your response...

Possibly the tests were done on the Nikon D3X, which has a 24MP sensor ?

JR

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Re: Imatest resolution question - lens testing
« Reply #3 on: November 07, 2011, 10:28:57 AM »
Oops!  You are right most of them are done with the D3x which has 24MP so that would explain it I guess.  I also understand I should not compare like for like different system but was just curious.

Thanks for pointing that out...
1DX, 24mm f1.4L II, 35mm f1.4L, 50mm f1.2L, 85mm f1.2L II, 135mm f2L, 24-70mm f2.8L II, 70-200mm f2.8L IS II :  D800, D4, and a whole bunch of Nikon lenses

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Re: Imatest resolution question - lens testing
« Reply #3 on: November 07, 2011, 10:28:57 AM »