Comparison of my 
Minolta AF 1.7 50mm (new)
against my 
Sony Alpha Kit Lens SAL 18-70mm
side view to
MC Rokkor-X PG 1.4 50mm

Hans-Joachim Weber (2007-05-08)


The Sony Alpha Kit lens most often is called to be a "good lens" in the range from wide to about 50mm. So I wanted to get familiar with the best possible image quality and its restrictions.

So I decided to compare my Kit lens coming with the Alpha 100 against my Minolta AF 1.7 50mm (new) that many years ago came to my lens collection. Those days I selected this example in a analog test from a couple of 4 pieces (I replaced my first example which never convinced me). Differences those days were not huge, but visible. So I am sure my AF 1.7 50mm is one of the better examples.  

I decided to shoot the old Wall I used over years also for my analog testing and that makes it possible to do a side comparison against my old beloved MC Rokkor-X PG 1.4 50mm. Here are both wall pictures taken with a heavy Manfrotto Tripod taken with the Alpha 100 at ISO 100 in Alpha Raw (ARW) format. I make a fair competition no sharpening was applied at any processing step Adobe Raw conversion with sharpening=0:


Picture 1: 
Alpha Mode A, conversion was done with Adobe Photoshop RAW converter with 0 sharpening
Left Picture: Kit lens SAL 3.5-5.6 18-70mm at 50mm f8    Right picture: Minolta AF 1.7 50mm at f8   

The distance from the wall is about 12m. Now let us take a look at a 100% crop near the center:

Picture 2: 
100% crops taken near the center of the pictures
IMHO as can be seen there is really no visible difference in the picture quality of both shots, both perform excellent!

But now let us take a look at a 100% crop in the lower right corner:

Picture 3: 
The 100% crops taken from the lower right corner tell us a total different story. 
Whereas the Kit lens clear misses sharpness the old prime at f8 shows what's possible!

The Minolta AF 1.7 50mm prime lens shows a clear advantage concerning corner sharpness. As seen here the Kit lens clear has reached its limits!

For some old Minolta manual focus fellows like me here now my cross view to a shot taken some years ago with my old Minolta XD5 and my sharpest 50mm lens ever, a MC Rokkor-X PG 1.4 50mm. I knew from the analog times that my AF 50mm primes lenses cannot really compete against my best Rokkor lenses concerning sharpness and the same here:

Picture 4:
Left picture: Alpha 100, 100% crop SAL 3.5-5.6 18-70mm 50mm f8 converted to (black and white)
Right picture: Taken 2004 with a Minolta XD5, MC Rokkor-X PG 1.4 50mm f5.6, Superia 100, 10000dpi Microscope, size reduced, no sharpening at all 

I know its not the usual way to get out the information of a analog film with a Microscope, but it clear shows what information a well exposed film can hold! But also with my Minolta Dimagescan 5400 dpi Scanner analog holds a very little advantage.


The Kit lens SAL 3.5-5.6 18-70mm shows very good center sharpness at 50mm f8 with no visible difference to the Minolta AF 1.7 50mm prime lens. The corners tell a complete different story and the prime lens leaves the Kit miles away here concerning sharpness. So the Kit is especially usefull for shots where good center sharpness is sufficent. 

The Minolta AF 1.7 50mm shows very good sharpness from center to edge at f8 and I am shure the 10MPixel Sensor of the Alpha 100 does not resolve all the lens can do at f8.

But than - the comparison with the old Rokkor - what a difference! Sharpness from another star. Guess what I take with me next weekend for my landscape photography?

(c) May 2007  

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