Konica LTM Sharpness comparison of Hexanon 35/2 UC vs. 35 Summicron ASPH.

[awilder]

Detail evaluation of a near infinity subject revealed some interesting but not unexpected results. First, the subject full frame at f/2 with the UC.

 

[awilder]

Now, Hexanon UC center detail at f/2, f/2.8 and f/4 from left to right.

 

[awilder]

Now, center detail with the Summicron ASPH. at f/2, f/2.8 and f/4.

 

[awilder]

Edge detail with the Hexanon UC at f/2 and f/4

 

[awilder]

Lastly, edge detail with the Summicron ASPH. at f/2 and f/4.

 

[awilder]

The interesting thing about the Hexanon in the center shots is that focus is optimised for f/2 and stopping down progressively softens. Its most likely due to focus shift from spherical aberration (SA) where the rf cam is likely optimised for the resultant focus at f/2. The central sharpness with the Summicron is less than the Hexanon at f/2 but it progressively improves by stopping down and by f/4 indicating the lens' rf cam is optimised for optical focus at f/4 or smaller. The softness at wider apertures maybe the effect of SA induced focus shift. At f/2.8 both lenses are equally sharp indicating a kind of intersection in focus. The slightly better edge performance of the Hexanon may be due to flatter field at infinity but I have other test samples shot at 70" where the Summicron clearly is sharper in the corner than the Hexanon as seen here: http://www.photo.net/photodb/folder?folder_id=711726. The figurines are positioned slightly forward so their rf focus is an exact match to the center target focus.

 

[jja]

I noticed a similar loss in sharpness as the Hex stopped down, and I could not explain it--I thought there might be a mistake in the posting. Thanks for the explanation.

From your samples, it looks like the Summicron has better shadow detail (she the shrubs/bushes).

 

[awilder]

No mistake in the posting, I double checked. I'm 99.99% certain the loss of central sharpness is simply due to focus shift from spherical aberration as described in the excerpts from the Konica technical report on the lens seen here: http://wiki.silvergrain.org/wiki/index.php?title=Konica_Hexar#Hexanon_35mm_f.2F2.0. Except for coating differences, optically the lens is identical to the Hexar AF as evidenced by the lens' block diagrams and MTF charts.

 

[espressogeek]

Heck, my UC gets so sharp at f stops above 4 it hurts. I need to look into this more or perhaps i dont ; -)

 

[awilder]

Interestingly, the sharpness of the Summicron and Hexanon are the same if you look at the crops shown below, right of center from the original full frame shot, both at f/4. The Summicron is the left and the Hexanon on the right.

 

[awilder]

Similarly, sharpness is about the same between the two lenses at f/2 and obviously slightly softer than above. The crops are in the same order as above.