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As a camera lens specialist, we are often asked for advise on choosing a new or used picture taking lens; often heard is
   - How Sharp Is It?
Bert Otten, a customer of ours and a specialist in optics has been testing various camera lenses over the years and has gone some way in answering the sharpness question.  He has kindly allowed us to publish his findings:

Resolution of some Medium and Large Format Lenses

The data below is based on measurements of resolution directly in the aerial image behind the lens, viewed through a microscope, of a test chart. Each time the magnification was chosen high enough so that the human eye would not be the limiting factor. It should be stressed that resolution itself is not sufficient information to decide on the quality of a photographic lens. Often manufacturers optimize the optics for high contrast at the cost of maximum resolution. That is why Modulation Transfer Functions (MTF curves) are used more often. Yet, the results of our resolution measurements are interesting enough to present them here, especially combined with the subjective contrast impression, rated along a scale from 1..10;

Lens Tested Test Aperture Resolution in lines / mm Observed Contrast 
(1 to 10)
Schneider SA 47mm / 5.6 MC f 5.6 320 8
Rodenstock Grandagon 65mm / 4.5 MC f 4.5 400 7
Rodenstock Sironar N 150mm / 5.6 MC f 5.6 300 8
Rodenstock Sironar N 150mm / 5.6 + Horseman 2x Converter f 11 120 7
       
Hasselblad CFL 40mm / 4 T* f 4 300 8
Horseman Super 65mm / 7 f 7 190 6
Hasselblad CB 80mm / 2.8 T* f 2.8 285 5
Hasselblad CB 80mm / 2.8 T* f 4 430 8
Hasselblad CF 80mm / 2.8 T* f 2.8 500 5
Hasselblad CF 80mm / 2.8 T* f 5.6 320 7
Horseman Prof. 105mm / 3.5 f 3.5 350 5
Hasselblad CF 150mm / 4 T* f 4 170 8
Horseman Prof. 180mm / 5.6 f 5.6 165 5
Fujinon T 300mm / 8 MC f 8 210 8
Hasselblad C 350mm / 5.6 T* f 5.6 160 5
       
Contax G 45mm / 2 f 2 530 6
Contax G 45mm / 2 f 4 450 8
Contax G 45mm / 2 f 16 100 8
Canon EF 50mm / 1.4 f 1.4 360 5
Sigma 105mm / 2.8 Macro f 2.8 380 7

Notes:
1)     Modern LF lenses tend to have better contrast than older lenses
2)     Older lenses can have very high resolution (Hasselblad CF, this one was 30 years old; Horseman 105/3.5)
3)     Low contrast is found:
     a)     at wide apertures of 35mm lenses
     b)     in some tele designs due to chromatic aberration
     c)      in older LF lenses
4)     Diffraction limited lenses exist (SA 47/5.6, Contax 45/2 at f4), but only in the central portions of the image
5)     In the aerial image of a lens you can find much higher resolutions than reported on film, due to limitations of the film.


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Revised: November 08, 2006 .