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Resolution of lenses - where are the limits?
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PostPosted: Mon May 05, 2008 8:08 am    Post subject: Resolution of lenses - where are the limits? Reply with quote
Hallo!
Sometimes i like to play with numbers.

The Zeiss Ultron - 3my - 330 lines per mm - is this true?

I don´t mean pairs of lines, only lines - white, black, white, black - any a line

The Tessar - only the half - 165 lines per mm

Pentax FA 50/1,4 f4,0 2320 lines over 16mm (sensorhigh) = 145 lines per mm on the K10d - more isn´t possible, this is the limit of the sensor in the centerarea

The Photozone-Test´s shows the interaction between objektiv and lens.
The borderresolution is lower, sometimes extrem.

How I can get more information about resolution of old lenses?

regards Peter


PostPosted: Mon May 05, 2008 4:18 pm    Post subject: Re: Resolution of lenses - where are the limits? Reply with quote
padiej wrote:
Hallo!
Sometimes i like to play with numbers.

The Zeiss Ultron - 3my - 330 lines per mm - is this true?

I don´t mean pairs of lines, only lines - white, black, white, black - any a line

The Tessar - only the half - 165 lines per mm

Pentax FA 50/1,4 f4,0 2320 lines over 16mm (sensorhigh) = 145 lines per mm on the K10d - more isn´t possible, this is the limit of the sensor in the centerarea

The Photozone-Test´s shows the interaction between objektiv and lens.
The borderresolution is lower, sometimes extrem.

How I can get more information about resolution of old lenses?

regards Peter


Very simple actually - you take the lens, put it on a calibrated optical bench and do your own Siemens star measurement through a 100x microscope, where you analyse the aerial image that lens produces for a given f-stop. (you could also use filters to see if it id different for blue, green or red for instance). This is what a friend I do from time to time for interesting candidates.

OR you have the patent data for instance of that lens and a lens design program where you plug in the lens data and have the MTF then computed via raytrace.

Sometimes I like to play with lenses like that....


PostPosted: Mon May 05, 2008 5:52 pm    Post subject: Reply with quote
Hallo!

There is an interaction between resolution and contrast, and more resolution is better for the contrast.
The resolution is a benchmark.
The Pentax K100d Sensor has 125 lines/mm in both direction. If I take the tessar 50/2,8, the lens is better and the sensor get clean informations.

If I try a ultron, I don´t know, if the better resolution would be visible, becouse the sensor is so limited.

The K20d is therefore a good investigation, this Sensor with 14MP will show the limits by many average lenses.


regards Peter


PostPosted: Mon May 05, 2008 9:20 pm    Post subject: Reply with quote
padiej wrote:

The Pentax K100d Sensor has 125 lines/mm in both direction. If I take the tessar 50/2,8, the lens is better and the sensor get clean informations.


The 125 lp/mm is only theory, because this is not a black and white sensor. The bayer-matrix and the AA-filter reduce this theoretical sensor resolution.

On the other hand, is the best lens performance only in the center and stopped down.

Ingo


PostPosted: Mon May 05, 2008 10:49 pm    Post subject: Reply with quote
How that discussion goes - shouldn't the title be renamed to
"Resolution of CAMERAS..." or do I need a doctor... Question


PostPosted: Tue May 06, 2008 7:21 am    Post subject: Reply with quote
Hallo!
Laughing or I need an analog Pentax



Of Course - I will buy a analog pentax, then I put a 50 ISO film inside and then, I can see, what the optic will do.

There are structures like a trumpet with a scale, then I can read the resolution, without a limited sensor.

So I can make a different between the lenses, and a analog Pentax would be very nice.

regards Peter
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