awilder
Alan Wilder
I've recently acquired good examples of the Rollei 35 and 35 S and decided to test them both critically with ISO 200 color negative film (the slowest commonly available due to the popularity of digital). My shooting is usually snapshots and landscapes so I restricted my testing to shooting distances of 2 meters and infinity. The 2 m tests were done with a sturdy tripod and 1954 USAF style resolution charts along with Norman Koren's MTF 40 contrast test charts and infinity testing was done with some houses at a distance from my backyard.
Results were surprising in some respects and not in others. At 2 meters centrally, the Sonnar delivers outstanding contrast and resolution at all stops compared to the Tessar especially from f/4 and smaller. Quality is on par with the best Leica lens I once owned. Centrally, the Tessar is very good, just not quite as good as the Sonnar. That said, I supect centrally the Tessar is actually an even better performer than my test indicated because setting the focus slightly past 2 m improves center sharpness at the expense of mid-frame performance.
Moving off axis to the mid-frame (midway between the center and edge), the Tessar's resolution of fine detail is a llittle better than the Sonnar until f/8. The Tessar's sharpness here is actually better than it's center which remains virtually unchanged regardless of aperture. The Sonnar is respectably sharp but at settings of f/5.6 or smaller and it catches up to the Tessar at f/8. The culprit is uncorrected astigmatism in the mid and outer zones causing fine details to appear a little bit smeary. The Tessar also has some astigmatism but mostly confined to the edge and corner.
Along the edge and corner, both appear to behave the same at matching apertures.
Infinity settings were similar in performance to 2 meters.
The Sonnar's performance was confirmed in a brochure showing the MTF 40 graph of the Rollei 40/2.8 Sonnar when the Rollei 35 RF was introduced years ago as seen here: http://www.rangefinderforum.com/forums/attachment.php?attachmentid=44196&d=1177382651, indicating my sample is a typical example. I would liken the Sonnar's peformance the pre-asphreric 50 Summilux-M which also has high central zone sharpness but moderate astigmatism in the mid-field and outer frame when the subject is along a flat plane. Fortunately, a curved subject plane mitigates the astigmatic effect so it's practically nil. This probably gives the Sonnar it's unique German optical signature compared to the Japanese contemporaries in the 70's that were Tessar and symmetrical Gauss designs.
In terms of practical use, the Rollei's 40/3.5 Tessar is ideal for flat field landscape and general use where sharpness across most of the frame is critical. A good example would be a city skyline image. The 40/2.8 Sonnar would be ideal if a faster aperture is needed with high central zone sharpness or the subject(s) of interest is located in a curved plane as in a more 3 dimensional arrangement. Also, unless you are a good distance estimator or using a rangefinder, most photographers having these scale focus cameras are using small enough apertues to cover any focusing errors which would also take care of the astigmatic aberration as well.
Results were surprising in some respects and not in others. At 2 meters centrally, the Sonnar delivers outstanding contrast and resolution at all stops compared to the Tessar especially from f/4 and smaller. Quality is on par with the best Leica lens I once owned. Centrally, the Tessar is very good, just not quite as good as the Sonnar. That said, I supect centrally the Tessar is actually an even better performer than my test indicated because setting the focus slightly past 2 m improves center sharpness at the expense of mid-frame performance.
Moving off axis to the mid-frame (midway between the center and edge), the Tessar's resolution of fine detail is a llittle better than the Sonnar until f/8. The Tessar's sharpness here is actually better than it's center which remains virtually unchanged regardless of aperture. The Sonnar is respectably sharp but at settings of f/5.6 or smaller and it catches up to the Tessar at f/8. The culprit is uncorrected astigmatism in the mid and outer zones causing fine details to appear a little bit smeary. The Tessar also has some astigmatism but mostly confined to the edge and corner.
Along the edge and corner, both appear to behave the same at matching apertures.
Infinity settings were similar in performance to 2 meters.
The Sonnar's performance was confirmed in a brochure showing the MTF 40 graph of the Rollei 40/2.8 Sonnar when the Rollei 35 RF was introduced years ago as seen here: http://www.rangefinderforum.com/forums/attachment.php?attachmentid=44196&d=1177382651, indicating my sample is a typical example. I would liken the Sonnar's peformance the pre-asphreric 50 Summilux-M which also has high central zone sharpness but moderate astigmatism in the mid-field and outer frame when the subject is along a flat plane. Fortunately, a curved subject plane mitigates the astigmatic effect so it's practically nil. This probably gives the Sonnar it's unique German optical signature compared to the Japanese contemporaries in the 70's that were Tessar and symmetrical Gauss designs.
In terms of practical use, the Rollei's 40/3.5 Tessar is ideal for flat field landscape and general use where sharpness across most of the frame is critical. A good example would be a city skyline image. The 40/2.8 Sonnar would be ideal if a faster aperture is needed with high central zone sharpness or the subject(s) of interest is located in a curved plane as in a more 3 dimensional arrangement. Also, unless you are a good distance estimator or using a rangefinder, most photographers having these scale focus cameras are using small enough apertues to cover any focusing errors which would also take care of the astigmatic aberration as well.
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