Hasselblad F-Distagon CFi 30mm f/3.5; Edge and corner Sharpness at 10X enlargement?

[thalmees]

Hasselblad F-Distagon CFi 30mm f/3.5; Edge and corner Sharpness?
Hello every body,
Thanks in advance for sharing your input.
What to expect in 22" square print, corners and edges, from Hasselblad Fisheye?
It's a 10.3X magnification.
Recently, was testing a clean sample of this lens.
Found that the edges(leave alone corners), are not as the lens was reputed as a super sharp corner to corner!
It's not! Sharpness at 10x starts to suffer in the last 20% or so each side.
Could it be the scale 10X enlargement?
Or a defect in the lens?
My prints are optical darkroom.
Target was more than 77 Yards away(230 feet), parallel line of buildings.
Center is super sharp.
Thanks for sharing your experience.

 

[thalmees]

Hello again,
Wish I'm not alone here!
The subject involve lots of determinants, but I prefer to let the scenario go as simple as possible to get simple answers as well.
What to expect at the edges of 22" print from F-Distagon at optimal f/stop?
Off course, compared to the center.

 

[Rod Klukas]

One thing I did not see in your query was what aperture did you use when the image was made. This lens is quite short for the format and so will tend to have a great deal of curvature of field which means that the edges will be not in the same plane as the center.
As this is a 10x enlargement from film and the human eye can resolve about 8 line pairs at 10", you need a resolution of about 60-80lpm across the entire field.
So you need to be shooting this image at about F 5.6-8 to fully cover in a reasonably even plane.
This plane flattens out as you stop down.

I would reshoot the scene or a wall and shoot all the stops and take a look at both center and edge with a 10X loupe until you find the one that is best for edge and center.
Print that one and see what you think.
Note the aperture.
Hope this helps.
Rod

 

[UdoS]

Simple answer: check the MTF curves. You can find them @ "Hasselbladhistorical-dot-com"

 

[Rod Klukas]

The MTF curves are helpful, but do not always show the full answer. The images always do.