An old lens argument when using film

BBR

BBR

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Brian
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It was about 40 years ago, I read a letter in AP regarding a lens review. And I have never forgotten (the gist of) it.

The letter was in response to a review. Two lenses had been reviewed, both had been used to take a picture of a room, in the corner was a classical guitar. Lens A was said to be clearly better because in the image taken with lens A , when magnified, you could see the guitar strings but in lens B you couldn't.

The letter came from professor who said, following some tests and calculations, that the image of the strings would be smaller than the silver halide (?) plates on the negative and therefore for the strings to show up, the light coming from them would have to be distorted. Therefore lens B was the better lens as it did not distort the light. Therefore, in this instance, the better lens was the one that showed less detail.

As I said it was 40 years ago and the full technical terms escape me but I wonder if the same argument could be applied today?
 
unless you've got silver halides on your sensor then maybe not
 
BBR said:
Well, if the image of the string was less than half the width of a pixel the same (theoretical) argument applies, surely?
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yeah but a pixel is probably 100+times smaller than a bit of silver halide so surely not seeable by the human eye hth mike.
 
BBR said:
Well, if the image of the string was less than half the width of a pixel the same (theoretical) argument applies, surely?
Click to expand...


No. If it was that thin it would alias.

Nyquist's sampling theory should solve it for you. The maximum frequency a sensor can resolve horizontally is 1/2 the Horizontal sampling frequency. So in HD, their are 1920 pixels per line and the maximum you can theoretically resolve is 960 pixel pairs (black and white) per line. However this would require exact alignment, no lens distortion and no movement. So the actual figure you would expect on a good camera is nearer 900.

But a DSLR is also a Bayer sensor which reduces resolution too.
 
kestral said:
The letter from the professor was complete rubbish.LOL
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To qualify your assertion kestral, can you provide the original image being discussed so we can see the position and relative size of the guitar in the frame?
 
so the prof said lens b was better because it didn't distort the light ,,,,,,,but maybe a lens that does distort the light is the better lens ,as it shows more ( in this case the strings ) hah ,
 
Alastair said:
To qualify your assertion kestral, can you provide the original image being discussed so we can see the position and relative size of the guitar in the frame?
Click to expand...

the op was by BBR Alastair ,,
 
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