update 16. Nov. 2005
Pentax Early Takumar Primes  
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  open LP/mm Center/Edge mid. LP/mm Center/Edge closed LP/mm Center/Edge Color Bokeh  
(P) Takumar 2.4/58mm (1957) f/2.4 44/ 39 f/4 56/ 56 f/8 44-56/ 70 **    
    contrast very low   low contrast   sharp edges; harmonic performance    
(P) Takumar 2.0/58mm (1957) f/2 39/ 31 f/4 70/ 44 f/8 70/ 70 **    
    chromatic aberration,
contrast very low
  low contrast   edges slightly dull; better sharpness than the 2.4/58mm  
(P) Takumar 2.2/55mm (1957) f/2.2 52/ 26 f/4 82/ 47 f/8 74/ 78      
    low contrast   stunning center performance        
A-Takumar 2.0/55mm (1959) f/2 65/ 41 f/4.8 74/ 52 f/9.5 82/ 82      
    low contrast       overall best sharpness in this comparison  
A-Takumar (Zebra) 1.8/55mm (1958) f/1.8 37/ 29 f/4 82/ 59 f/8 82-94/ 74      
    chromatic aberration,
low contrast
A-Takumar (black) 1.8/55mm (1962) f/1.8 65/ 26 f/4 37/ 41 f/8 74/ 74      
    contrast very low   low contrast, out of foucs?          
SMC-Tak. 1.4/50mm (1972) f/1.4 40/ 36 f/4 32/ 40 f/8 81/ 72      
        out of focus?          
Isco A.-Westagon 1.9/50mm f/1.9 36-32/ 36-23   working only at full aperture      
A-Tak. 3.5/35mm (1959) f/3.5 73/ 59-51 f/8 73/ 65-51 f/11 81-73/ 73-65      
    slight light-falloff to the edges            
A-Tak. 2.3/35mm (1959) f/2.3 37/ 32 f/4 59/ 46 f/8 81/ 73      
Carl Zeiss Jena 2.4/35 mm f/2.4 40/ 32-40 f/4 46/ 46-37 f/9.5 59/ 51      
How the test was performed:  
Camera (Pentax SP-1000) standing on a wodden tripod, exposure-times 1/1000s - 1/30s with air pressure bulb attached to the trigger  
Film: Fuji Sensia 100 ASA Color Slide film. My feel is that the grain of this particular film limits the resolution to about approx. 85-90 line-pairs per millimeter) - but this is my "common" slide film. Maybe Sensia has a somewhat finer grain  
Object: My neighbor's barn side in my garden, 8.5m distance. The camera position wasn't moved when changing focal lengths. Scale of focus: 58MM: 146.6 55MM: 154.6 50MM: 170 35MM: 242,9  
Focussing: At the center chart. With the f/1.4 wide open at both charts (2 pictures)  
3 pictures for each lens: wide open, at f/4 and f/8. At some lenses, according to TTL-metering of the camera, half stop more because the camera makes no shutter times "in-between". TTL measurings turns out to be precise.  
Not finished: Comaprison with my SMC-M Takumar 1.7/50mm at my Pentax MX; Zeiss Planar 1.4/50 and Voigtländer Color-Ultron (1.8/50mm) at my Rolleiflex SL350  
Two exposures noted in italic may be slightly out-of-focus (not equal distance for all targets): Maybe the 1.8/55m Zebra wide open is also slightly off  
Weather: no direct sun, a bit cloudy. Not equal light at every picture  
Evaluation: MGF optical microscope, 60x. Two figures (value1-value2) means different tangential and sagittal resolution figures   
Targets: Two USAF-test charts, tomatoes placed on a plate, autumn leaves and twigs of a small tree. No real big contrasts  
Scanning: My Plustek ST48, although 2400x4800dpi capable according to spec, don't show the deatils which can be seen in microscope. Pictures just for imagination how the test was proceeded  
Results: The test shows that vintage Pentax lenses are capable of doing a good job for today's standard with normal film, even if some lacks of overall contrast at larger apertures. What can be hardly described is the color rendition of the 58mm lenses (Heliar and Sonnar types) which looks nicer than with later types.
The "Gaussian Types" (even the 5-elements 2.2/55 Takumar) show higher sharpness and slightly better contrast wide open. This was probably the reason why the 58mm designs were ceased in 1958.  
Wideangle lenses: The 2.3/35 is somewhat weaker wide open than the (very strong) 3.5/35mm. At large apertures hardly any difference in sharpness to detect (the 2.3 slightly better)  
Both German M42 lenses in this evaluation didn't match the quality of the Takumar lenses, both in overall impression of the results and resolution figures  
© Frank Mechelhoff, NEW 1.November 2005  
(Pictures can be seen only with Mozilla Firefox for some reasons; please ask Mr. B.Gates why...)  


...Example: Auto-Takumar 2.0/55mm (1959)

...Example: (Preset-) Takumar 2.4/58mm (1957)

...Example: (Preset-) Takumar 2.0/58mm (1957)





Bookeh comparison

bookeh 2.0/58mm  bookeh 2.4
 Comparison of "bookeh" (background unsharpness): left Takumar 2.0/58mm (1957), right Takumar 2.4/58mm (1957), both wide open.
 The 2.0/58mm looks better, less disturbed. Even if the sharpness wide open is better than the 2.0/58mm, the 5-elements Heliar type design
 of the f/2.4 lens seems to be overstrained a bit. The 2.0/58mm shows a charateristic typical for the Sonnar family (6 elements) it belongs to.