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

[alentine]

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.

 

[Sirius Glass]

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.

Try the SWC which is rectilinearly correct. I do not like the fisheye because I do not find it very useful and I do not like photographs which include my shoes. I passed up a fisheye for a great price and the sales person at Samys said that I made a good choice and he felt the same way.

 

[alentine]

Try the SWC which is rectilinearly correct. I do not like the fisheye because I do not find it very useful and I do not like photographs which include my shoes. I passed up a fisheye for a great price and the sales person at Samys said that I made a good choice and he felt the same way.

Thanks so much Sirius Glass,
Was planning to communicate with you on private message.
Thanks indeed for your post.
You are correct, but It's my long time dream, not easy to leave F-Distagon go, if it's Ok.
Regardless of any other causes apart from the lens itself, is it expected that F-Distagon should show any degree of unsharpness in the edges at 10X enlargement?
Thanks.c

 

[Chris Livsey]

If you take a moment to study the Zeiss MTF diagrams you will see why the edges are not "sharp'.
http://www.hasselbladhistorical.eu/pdf/LDS/CF30.pdf

Just as a check you are shooting with a neutral filter in place? A filter is part of the optical system and must be used

 

[alentine]

If you take a moment to study the Zeiss MTF diagrams you will see why the edges are not "sharp'.
http://www.hasselbladhistorical.eu/pdf/LDS/CF30.pdf
Just as a check you are shooting with a neutral filter in place? A filter is part of the optical system and must be used

Hello Chris,
Thanks for your post.
Yes, the neutral filter is installed.
The MTF shows that the Sagittal 40LP/mm is 60% or above except the last 10% only(that 10% is not edges, it's well in the corners).
The Tangential 40LP/mm is below 40% in the last 25% of the frame diameter.
But hasselblad when represented it's SWC performance, they used the Sagittal line only of the 20LP/mm.
The Sagittal 20LP/mm of the F-Distagon is 80% or above all the way until the last mm in the corners. That's even better than the same line and orientation of the Biogon/SWC.
But please consider that the subject size is smaller 21% in the F-Distagon 30mm compared to the subject size of Biogon 38mm.
Centeral 60% area of the F-Distagon, is super sharp as expected.
Let me ask in another way:
Is 10X enlargement too much, for a short focal length like 30mm, to let peripheral defects appear clearly?
Thanks.

 

[ic-racer]

Is this a question about the enlarging lens or the camera lens? If the corners of the negative are sharp then there is an issue with the enlarging process.

 

[Chris Livsey]

Hello Chris,
Thanks for your post.
Is 10X enlargement too much, for a short focal length like 30mm, to let peripheral defects appear clearly?
Thanks.

I have only shot the lens, a borrowed copy, on a P20 back so cropping out the extremes but that is not the same as shooting film full frame which is why I didn't add that experience. I presume and again forgive me as for the filters that the enlarger set up is proven to give even sharp results at 10X from a known good lens? Again is this softness "even" you mention corners, as there may be de-centring in the lens ?
The MTF does show a falloff, perhaps the excellent centre is giving unrealistic expectations from the edges?
Finally, what are you viewing at? You could go to 16ft square if viewing at 50ft minimum, are you comparing with known good lens at 10x on your system?
What we need is someone who has one and prints optically. I'm sorry that's not me.

 

[alentine]

Is this a question about the enlarging lens or the camera lens? If the corners of the negative are sharp then there is an issue with the enlarging process.

Thank you ic,
Asking only about the taking camera lens, assuming any other factor is neutral.
What to expect at the edges of 22" print?
I do not wish to complicate the scenario, just to get answers that could enlighten the issue.
Thanks.

 

[alentine]

...
the enlarger set up is proven to give even sharp results at 10X from a known good lens?
Again is this softness "even" you mention corners, as there may be de-centring in the lens ?
...

Thank you soooo much Chris.
Please consider that the enlarger, enlarging lens and easel, have no issue.
I know, subject involve lots of variables, but I prefer to let the scenario simple to get simple answers as well.
Yes, the softness is very symmetrical.

...
The MTF does show a falloff, perhaps the excellent centre is giving unrealistic expectations from the edges?
...

It could be true.
I have the hypothesis, but, when I remember the consensus around this lens, "sharp, corner to corner", I could not accept it, due to the degree of softness and area that involved(20% each side).

...
Finally, what are you viewing at? You could go to 16ft square if viewing at 50ft minimum,
are you comparing with known good lens at 10x on your system?
...

A print that size(image is 22" square), I used to view it in my hands outstretched, and in day light, not room light.
Which is about 23" from my eyes.
When examining the print, I bring my eyes to the nearest possible point, considering to scan all areas of the print at the same distance.
Unfortunately, I do not have a reference to compare with.
The subject involve lots of determinants, but I prefer to let the scenario go as simple as possible to get simple answers as well.
Thank you so much Chris.

 

[Chris Livsey]

I have the hypothesis, but, when I remember the consensus around this lens, "sharp, corner to corner", I could not accept it, due to the degree of softness and area that involved(20% each side).

I don't think there is a wider consensus: that "sharp, corner to corner" statement appears in the Hasselblad Manuals, such as Wildi's and in their marketing material, its widespread appearance in articles that mention the lens is largely due to lazy writers copying that catchy phrase from their research of those sources and so on it perpetuates. There may be independent reviews out there but honestly is it worth finding them?
Zeiss do not make that claim:
The excellent correction of this lens results in outstanding sharpness, even at initial aperture.
As you say the centre is very sharp, and they don't say where it is sharp and that "claim" has disappeared from the Zeiss year 2,000 paper on the CFi version.
http://www.hasselbladhistorical.eu/pdf/LDS/CFi30.pdf

Now there will be copy to copy variation and the copy you are testing may be an outlier and may have been roughly handled over the years so may not be representative, the Lens Rentals testers will not quote MTF results etc with less than 10 copies to hand and the variation is always present, even in top price glass from top rank makers. Test another copy if possible, I don't know where you are but the Hasselblad Hire service does list that lens for rental in major markets.

 

[Sirius Glass]

Thanks so much Sirius Glass,
Was planning to communicate with you on private message.
Thanks indeed for your post.
You are correct, but It's my long time dream, not easy to leave F-Distagon go, if it's Ok.
Regardless of any other causes apart from the lens itself, is it expected that F-Distagon should show any degree of unsharpness in the edges at 10X enlargement?
Thanks.c

I have no experience with the lens but the specifications look great as expected.
http://www.hasselbladhistorical.eu/pdf/LDS/CFi30.pdf

 

[alentine]

I have no experience with the lens but the specifications look great as expected.
http://www.hasselbladhistorical.eu/pdf/LDS/CFi30.pdf

On the other hand, I did not find any reason in the lens itself that could point to expect bad performance.
The lens is mint, no single scratch to the body and glass is crystal clear. Has all filters mint also.
It has been made in 2001.
Could not imagin any mistreatment during its age.
Enlarger is aligned, printing lens is high quality. Softness is symmetrical 20% each side.
At this moment, may I ask Hasselblad owners what they expect at the edges of a 10X enlargement from Zeiss wide angle lenses?
Though it's 6X6, it's effectively 645 format(54x41mm).
Is it too much 10X enlargement? Considering small subject rendering of 30mm lens?
I do not know why I'm refusing the idea that the lens is performing bad?
But, persistently not happy with that degree of edge softness.
Could it be a bad interpretation of the MTF curves? Which could assumes higher or lower performance than what actually should be expected?
How can the Tangential 40lp/mm being below 40% performance, be read in the lateral 65% of the image height? It's only in the central 20% of image height this line performing above 60% performance.
But, the Sagittal 40lp/mm is above 60% performance in 90% of image height.
I'm sorry, being persistent.
Thanks everybody for your input.

 

[RalphLambrecht]

Thanks so much Sirius Glass,
Was planning to communicate with you on private message.
Thanks indeed for your post.
You are correct, but It's my long time dream, not easy to leave F-Distagon go, if it's Ok.
Regardless of any other causes apart from the lens itself, is it expected that F-Distagon should show any degree of unsharpness in the edges at 10X enlargement?
Thanks.c

The widest lens I use on the Hasselblad is the 40mm DistagonFLE and it is super sharp. No need to go any wider for me.

 

[BrianShaw]

At what aperture are you noticing the softness, all?

 

[Sirius Glass]

A ten times enlargement is not asking too much.
A fisheye is a very specialized lens with in my not so humble opinion [IMNSHO] has limited usage. I do not know if the softness in the corners is normal. As I stated the widest Zeiss lens I use is the SWC [38mm] which is sharp in the corners.

 

[alentine]

Thanks so much all for your kind input.
And my apologies for the late reply.
I did another two(2) sets of tests, because the first test was not super methodological and was choosing the best edge sharpness negative among other negatives by a well made 10X loupe, then printing to the same scale 10X.
Most of the second test set already developed, and can conclude based on examining under my 10X loupe.
Nine(9) films up to now!
Please continue discussion.
Thanks so much.

 

[alentine]

At what aperture are you noticing the softness, all?

Thanks so much Brian for your question.
Was not able to answer you accurately before I conducted the second set of tests.
Now, I can confidently say:
The edge(not corners) sharpness is improving with closing down.
Not good at all at f/3.5, clear unsharpness at f/8, and best sharpness was somewhere at the range of f/16~f/22.
It improves very gradually but does not at all reach the center sharpness at any f/stop.
Center sharpness on the other hand reaches its max at f/8. Start to decrease with closing down after f/8.
But, at f/11, f/11.5 and may be f/16, the center sharpness still high for a 10X enlargement.
Thanks Brian, and thanks all for studying the following table:
Absolute numbers and relative impressions do not means too much.
But, when related to a certain reference, it can give much better understanding.
All numbers in the table are estimations related directly to the best sharpness achieved by the lens(given 10/10), which was at f/8 and in the center of the negative.
.

.
Now, is this shape of performance expected from F-Distagon?
Thanks indeed.

 

[alentine]

The following is a quote from: http://www.hasselbladhistorical.eu/pdf/LDS/CFi30.pdf
Left column, 6th to 10th line.
Thanks Chris for the link.
" ... It has been designed as a special lens for scientific and technical documentation and offers therefore outstanding image quality and very even illumination from corner to corner – and all this even at wide open aperture. ... "
To me, it looks that the lens I'm testing to decide for keeping it or not, is not performing as it should, unless the evenness that Zeiss is talking about is for illumination and not sharpness!
Thanks for sharing your input and experience.
.
As for the MTF, and specially the Tangential/Meridional lines, I've found this:
https://www.zeiss.com/content/dam/Photography/new/pdf/en/cln_archiv/cln30_en_web_special_mtf_01.pdf
.

.
I added the MTF curves of F-Distagon at f/8, in the lower left of the Zeiss page for comparison.
What I knew after reading again about MTF charts is, waving lines(Sagittal) means field curvature or maybe what Zeiss call it: focus shift.
This page added the effect of low performance Tangential lines.
I think there is similarity between the MTF chart of the lens in the right upper part of the page, and the MTF of Hasselblad F-Distagon.
BTW, lenses compared in Zeiss document page, are from small format, not medium format.
The small photos inside had no manipulation what so ever.
.
I do not know really if I'm just trying to find an excuse to the low sharpness in the edges at 10X enlargement from F-Distagon.
Could the lens be just over rated and I'm expecting too much?
Thanks for your input.

 

[ic-racer]

This is a tough question. Your testing looks like it was done very well, the numbers make sense for lens test but you really need someone with another lens to check. I'd let you know my results, but I have the 40mm Zeiss Distagon and the numbers would be useless to you.

I do have the Zeiss 16mm fisheye and Yashica 15mm fisheye for 35mm and can say they are much sharper in the 4 corners than the Zeiss 18mm rectilinear SLR retrofocus lens.

I don't recall, but I think this print was made from a negative exposed with the Yashica 15mm Fisheye.

Interesting thing about this picture is these icicles were just tiny things. I suspect many photographers would have just walked right on by.

 

[fdonadio]

The fisheye is traditionally used by skateboarding photographers (like me) just because of this, @ic-racer!

The center of the frame gets “pushed away” farther than the borders — that’s why the icicles in the top of your photo look the same size as those in the middle. In a skateboarding photo, using the right framing, the skater looks much higher than (s)he is and obstacles look bigger.

Pretty much every fisheye I have seen has this characteristic and maybe that’s why the corners are not so sharp as the center.

I have the 30mm f/3.5 for my Hasselblad, but I have never tried to assess its sharpness at all. I only use it for skateboarding and customers in this market are not interested in “technicalities”.

Edit: “assess”, not “access”!

 

[ic-racer]

That is great that you are using film for skateboard photography.

 

[fdonadio]

That is great that you are using film for skateboard photography.

Thanks! I use film for everything, except for everyday snapshots, for which I use my phone. I am getting used to take my Nikon FM2 wherever I go.

I shot an “old school” skateboarding contest a couple of weeks ago and did it accordingly: FM2, Zenitar 16mm f/2.8, Metz 45 flashes and Eastman Double-X. I also used a Nikkor 35-105mm for some shots.

 

[alentine]

Hello everyone,
Just to add something related well to the topic of this thread. A sample MTF accompanied with text analysis of the significance of deviated tangential curve on image appearance.
To me, it’s a great resource to the thread and topic.
https://www.opticallimits.com/mtf
“ An example for a lens performing relatively good in contrast but showing only a limited ability to transmit very fine structures ( tangentially at 40 lp/mm) ”
Among discussion of other MTF curves on the same page.
The page does not comment on the field curvature in the example MTF.
The next MTF example, belongs to the text quote above.

Hope this adds to a better understanding of the topic, though I believe without a simple and clear method of visual correlation of MTF the topic will stay unclear and subject to opinions rather than to a solid tested parameters.
Thanks everybody.

The following is a quote from: http://www.hasselbladhistorical.eu/pdf/LDS/CFi30.pdf
Left column, 6th to 10th line.
Thanks Chris for the link.
" ... It has been designed as a special lens for scientific and technical documentation and offers therefore outstanding image quality and very even illumination from corner to corner – and all this even at wide open aperture. ... "
To me, it looks that the lens I'm testing to decide for keeping it or not, is not performing as it should, unless the evenness that Zeiss is talking about is for illumination and not sharpness!
Thanks for sharing your input and experience.
.
As for the MTF, and specially the Tangential/Meridional lines, I've found this:
https://www.zeiss.com/content/dam/Photography/new/pdf/en/cln_archiv/cln30_en_web_special_mtf_01.pdf
.
View attachment 191941
.
I added the MTF curves of F-Distagon at f/8, in the lower left of the Zeiss page for comparison.
What I knew after reading again about MTF charts is, waving lines(Sagittal) means field curvature or maybe what Zeiss call it: focus shift.
This page added the effect of low performance Tangential lines.
I think there is similarity between the MTF chart of the lens in the right upper part of the page, and the MTF of Hasselblad F-Distagon.
BTW, lenses compared in Zeiss document page, are from small format, not medium format.
The small photos inside had no manipulation what so ever.
.
I do not know really if I'm just trying to find an excuse to the low sharpness in the edges at 10X enlargement from F-Distagon.
Could the lens be just over rated and I'm expecting too much?
Thanks for your input.

 

[RalphLambrecht]

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.

goole the MTF for it,which will tell all.

 

[Ai Print]

The widest lens I use on the Hasselblad is the 40mm DistagonFLE and it is super sharp. No need to go any wider for me.

Same here, great lens too, 40mm is very wide for a square format image.

Every time I think about an SWC I remember the price tag to one-trick-pony ratio and scratch the idea.