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Author Topic: Lens resolution or Sensor Design?http://www.nemeng  (Read 2614 times)
Ben Rubinstein
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« on: August 07, 2005, 07:47:13 AM »
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All someone has to do is show that the same sharpness issues exist with film and that is that.
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lester_wareham
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« Reply #1 on: August 07, 2005, 12:23:36 PM »
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All someone has to do is show that the same sharpness issues exist with film and that is that.
I think the problem mentioned is particular to digital and is caused by the little lenses at the sensor sites. This causes a problem that looks rather like chromatic aberation.

Aparently the solution is a telecentric like lens design with less angle of incidence on the corners (exit node further away from the image plane).

I think some of Nikons lens designs use this method. Odd as they don't have a FF sensor yet.
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lester_wareham
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« Reply #2 on: August 11, 2005, 05:51:30 AM »
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All you have to do is shoot with the wide Nikkors to see just how well they do perform on a 1DsMKII. They are a couple of millimeters further from the film plane than Canon, and it seems to make all the difference - even with 20 year old lenses.
Well the lens mount to image plane distance is not all the story as it depends where the exit node is which could be behind the element with a retrofocus design.

I am not sure if there is more to this telecentric than the location of the exit node. Any searches I do on it just come up with 'machine vision' research papers....

However, I have heard your observation about nikon WA from others so I am sure you are correct.

This remineds me, my father-in-law has a stack of old nikon lenses, including ultra wides and T&Ss. Perhaps I should get hold of the nikon to canon mount convertor. Manual focus is not an issue for me particularly with those lenses.
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David R. Gurtcheff
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« Reply #3 on: August 11, 2005, 03:50:17 PM »
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Has anyone tried some of the older screw mount Takumars on a 1Ds MkII? I have the Cameraquest adapter, and a collection of older Takumars: 24mm f3.5, 28mm f3.5, 50mm f1.4, the very old 35mm semi-auto f2.3, and the likewise old 105mm semi-auto f2.8. I recall from my film days that the 105 Takumar was extremely sharp. I am particulary interested in the wide angle performance with the MkII for landscape, tripod work. The weather here on the NJ coast is hazy, hot and humid....not photographic weather, so I have not yet tried these old lenses. I also have seveal manual Nikors, including a 28mm, so I am interested also in hearing about their performance on a MkII.
Thanks for any feed back.
Dave
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Craig Arnold
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« Reply #4 on: August 07, 2005, 02:51:59 AM »
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Michael et al seems to believe that on the 1DsMkII there is a problem with the sensor out-resolving the available wide-angle lenses.

There is an alternative view which I found when researching the likelihood of a FF digital-M Leica.

The reason it's so hard to do a digital M is that the light strikes the film plane at a steeper angle than an SLR, and sensors can't cope with this very well, film of course doesn't mind. The assertion is that this same problem crops up on cameras like the the 1DsMkII at the corner of the frame and is frequently mis-identified as a problem with the lens.

http://www.nemeng.com/leica/004f.shtml

Your thoughts?
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Jonathan Wienke
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« Reply #5 on: August 07, 2005, 12:19:59 PM »
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The reason it's so hard to do a digital M is that the light strikes the film plane at a steeper angle than an SLR, and sensors can't cope with this very well, film of course doesn't mind. The assertion is that this same problem crops up on cameras like the the 1DsMkII at the corner of the frame and is frequently mis-identified as a problem with the lens.
That is an old urban legend, dating back prior to the introduction if the 1Ds. There is a rather easy solution to this "problem", which involves laying the microlenses down on the sensor surface with a slightly narrower spacing than the sensor pixels. The microlenses are centered over the pixels at the center of the sensor, but are offset inward at the edges, so that light striking the sensor at an angle can be efficiently utilized. In any event, failure to use this technique would only increase vignetting, but would have very little effect on chromatic aberration. Given the fact that most 1Ds-film comparisons show similar levels of vignetting when the same lens is used on the film and digital bodies, there's no real-world evidence that this theory has any validity. If the lens is closer to the sensor, all that is necessary is to increase the edge microlens offset accordingly.

The real issue is that silicon records more image data than the same area of film, making lens flaws that used to be hidden in the grain structure visible and obvious.
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pfigen
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« Reply #6 on: August 07, 2005, 06:02:31 PM »
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"I think some of Nikons lens designs use this method. Odd as they don't have a FF sensor yet."

All you have to do is shoot with the wide Nikkors to see just how well they do perform on a 1DsMKII. They are a couple of millimeters further from the film plane than Canon, and it seems to make all the difference - even with 20 year old lenses.
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pfigen
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« Reply #7 on: August 11, 2005, 03:27:26 PM »
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"Well the lens mount to image plane distance is not all the story as it depends where the exit node is which could be behind the element with a retrofocus design."

I realize that, but it certainly can't hurt that the lenses are a few millimeters further from the film plane. The lenses I have used with excellent results are the 16mm 2.8 fisheye - an unbelievably sharp lens. The older 18mm 3.5, which is better than the newer 2.8, and the venerable classic, the 24mm 2.8. Another worth mentioning, although not wide, is the 180 2.8 ED, which is very good, even wide open.

For most applications, autofocus is not an issue for me either, but I certainly have a bunch of Canon AF glass when I do need that. I use the Cameraquest adapters.
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