Young enthusiast looking for a digital back for my Hasselblad 500 C

[Pieter12]

Ahhh ok
got it!

I am still testing the camera and i am so sorry but i have new questions now about cromatic aberation and sharpness i testet first my CF 50:

View attachment 424658

then my 80 c

View attachment 424659

a lot lot better both iso 50 f 11 t15

is that nominal or is something wrong, or do
we now see thing with the sensor with 39mpx which where impossible to see on film?

You will see a difference in sharpness if the sensor is not in the same plane as the film. As well as chromatic aberration/color fringing along the edges of the image with wide angle lenses, due to the angle of the light hitting the sensor.

 

[12557]

Yes ofc but the Sensor fits perfectly, there is no chance that the sensor is on a wrong plane, everthing is original, so is the not shparness normal?

As well as chromatic aberration/color fringing along the edges of the image with wide angle lenses, due to the angle of the light hitting the sensor.

Ofc yes but good one like my rodenstock for my lohhof is perfect perfect in sharpens and has any aberration

So how are yours on 80 and 50?


thank you guys!

 

[itsdoable]

I can't really tell much from the resolution of the posted pictures.

Your 50 that you posted is a FLE, was the FLE element set to infinity?

These backs were often individually shimmed for the camera body, as the precision required for a digital sensor is higher than for film. I would do a focus test with any new2me digital back first to see how well registered it is. Then you can test your lenses.

 

[12557]

Yes, the 50mm is an FLE, and I had the ring set to infinity — that part is correct.





Regarding the resolution, I made screenshots: one at 300% zoom and the larger image at 100%.





You mentioned that these systems were sometimes adjusted to the body. How exactly was that adjustment done?





And how would I test, without a lens, whether the digital back itself is actually focusing/sharp?

 

[Pieter12]

And how would I test, without a lens, whether the digital back itself is actually focusing/sharp?

I believe that like film, the sensor itself has no focus, just its placement in the plane of focus.

 

[_T_]

If the sensor was out of the correct flange focal distance the camera would focus slightly nearer or farther than where you set the plane of focus according to the viewfinder, but some part(s) of the image would still be in perfect focus.

You can test this by taking a picture of a ruler placed parallel to the axis of the lens. If the marking on the ruler that you focus on in the viewfinder is in sharp focus in the image then you know that the sensor is in the correct position.

 

[itsdoable]

Regarding the resolution, I made screenshots: one at 300% zoom and the larger image at 100%.

The 300% always looks less sharp than the 100%. Hard to compare.

You mentioned that these systems were sometimes adjusted to the body. How exactly was that adjustment done?


And how would I test, without a lens, whether the digital back itself is actually focusing/sharp?

The test is to see if the focusing screen is in the same place as the sensor or film, that is if you focus perfectly on the screen, where is the focus on the film or sensor - often SLR can be front or back focused. This is most noticeable on fast long lenses, so those are the best for testing. In this case the focus screen can be shimmed, or the mirror stop can be adjusted, or the film plane/sensor plane can be adjusted. Early digital backs all had shims mounting the sensor in the back, so they could be adjusted to match a camera body, for instance the Planar 2/110 can be quite sensitive to this. I had a 3rd party screen on my Hasselblad which worked fine in the film days, and when I got the 2/110, I noticed it was back focusing, then inspecting my film shots, I could see that many of them were slightly back focused. Adjusting the screen position, or replacing it with an acute matte solved the issue.

This is a typical focus tester

You focus on the target, and in the resulting picture you can see where on the sloped scale where the sensor is actually focusing on.


Even though I have a home made one, I often just use our the front stoop.

For best sensitivity, use a fast long lens, focused close, wide open. I focus on the wood block, and I can see where the sensor is in focus - this was post adjustment for an infrared sensor, the focus screen has been shimmed to focus in visible light where the sensor would focus in infrared. Initially, the ground behind the block was in focus (back focusing)

This also can show if this lens has field curvature or some tilt.

 

[12557]

I understand exactly what you mean, and it makes complete sense to me.

I recently had the focusing screen (ground glass) adjusted, but at that time I was still shooting film. From my images, I do get the impression that the focus may be shifted forward, but I’ll test that more carefully now.


What I don’t fully understand—and I’ll send you some example images later—is that I have the feeling that nowhere in the image the sharpness is really good. If helpful, I can send the files in full resolution.


If that is indeed the case, wouldn’t that suggest that the sensor is not positioned correctly in the digital back? I can’t see any adjustment options on my P45, since it simply locks into place on the rear mount.


Also, in both test shots the lens was set to infinity, so at least the more distant objects should be absolutely tack sharp.

And regarding the lens I would use for the focusing screen test: my longest lens is the 80mm, and I would test it wide open at f/2.8 — correct?

ang again thank you for your help!

 

[12557]

I did that test and it super ok!

80CF f:2,8 t:125 view: 100% :

50CF view: 100% a litte cropped and smaller and crompresset in due to the 2mb limit

80CF view: 100% a litte cropped and smaller and crompresset in due to the 2mb limit


i am excited for your opinion!

 

[12557]

On that day it was very windy!

 

[itsdoable]

That looks pretty nominal to me. I assume you focused on the yellow warning label of the cigarette box?

The 2 pictures look OK to me (being 100% with the compression). Maybe others can comment (or you can ask in a digital forum) as I'm not a pixel peeper, but it looks typical of the output. Keep in mind that these backs do minimal sharpening and no contrast processing, and at 100% you should start to see some softness due to the demosaic algorithm. I find its difficult to assess sharpness with green foliage, especially against the sky, as residual chromatic aberrations and purple fringing (which is a property of the sensor CFA and well depths) tend to overpower.

 

[12557]

Okay, thanks for your assessment. No, I actually focused on the small text in the red area on the front, and in my opinion that part does look 100% sharp. So that’s already a good sign.





My concern was more about the overall sharpness of the image. But maybe I need to get a second opinion elsewhere, or perhaps others here will still comment.





Curious to see what others think.

 

[_T_]

It’s hard to tell from the description what you did to the photos.

I think you resampled the image to a lower resolution, which would make it impossible to see if the file looks sharp.

What you would need to post so that we can see the sharpness of the image is a crop of small portion of the original file including <2000x2000px of the sharpest part of the original image. If you resize the image to fit the file size requirements we can’t tell if it’s sharp, and you can’t upload the original file because it’s too big, so you have to give us a smaller piece of the image without doing any resampling.

 

[12557]

So again 2000x2000px export form capture one on JPG

 

[12557]

Hey Guys last question!


Where can I find, or is there a place here in the forum or in another forum, where I could find experts who discuss the technical details of vintage digital backs in depth? Is there perhaps a suitable thread here? So far I haven't found anything. And until then, many thanks again for your support over the past months.

Kindest, Matthias

 

[Pieter12]

Try getdpi. There is a forum for medium format with digital backs.

 

[Alexander6x6]

Try getdpi. There is a forum for medium format with digital backs.

Getdpi does not work for newcomers. I tried it a couple of years ago and, although you can complete the registration process, you won't receive a response. Sending personal email messages to the moderators won't help either.
I also tried the hybrid section of this forum, but unfortunately it was a dead end.

 

[itsdoable]

Getdpi does not work for newcomers. I tried it a couple of years ago and, although you can complete the registration process, you won't receive a response. Sending personal email messages to the moderators won't help either.
I also tried the hybrid section of this forum, but unfortunately it was a dead end.

Perhaps they have fixed that issue, the OP was able to post a question there.

Phase One P45 on V-system: softness normal or not

Hey Community! I've been shooting with a Phase One P45 on a Hasselblad 500C with Planar C 80 T and a 50 for a few months now. My first experience with a digital back on V-system bodies. Overall I'm very happy with the back, but I have some questions about overall sharpness that I'd appreciate...

www.getdpi.com

 

[Alexander6x6]

Perhaps they have fixed that issue, the OP was able to post a question there.

Thanks a lot! They fixed it in March this year.