85mm f1.2 on Medium Format

[Audii-Dudii]

One question I have is why you had to hack the lens and the SLR camera to get them to working? Why did you not consider the other possibilities that does not include a mirror? Now you know that the mirror isn't all that useful.

A Kapture Group Truewide camera accepts digital backs, has a shutter, and can be adapted to accept Contax lenses, but it really has to be used on a tripod, which I think would limit its usefulness for his purposes.

 

[Vivek]

The results from Marko are superb!

I am just trying to discuss the possibilities related to the gear. Given that the mirror isn't really useful for focusing and there is no TTL metering, tripod bound cams would be least of the concerns. No?

 

[PSon]

1. Mirrorless camera with small sensor size (currently a max size of 1.5 x 135mm format full frame) will increase depth of field. Also mirrorless cameras have AA filter with the exception of the Fuji which has not been released. Furthermore, CCD versus CMOS sensor are different. The point of the original poster intended to create less depth of field by using a bigger chip (MFDB) and the CCD chip looks similar to the 1.3 crop factor Leica DMR and the current full frame Leica M9. All the 135mm format Leica cameras have CCD chip looks despite limited to only 135mm full frame or less.

2. Kapturegroup True Wide uses a copal shutter and it has issue with slow shutter speed (ghosting). The camera cannot be handheld and view with the optical finder for the original poster style of shooting. The application for the Truewide camera is for tripod application.

3. Similar to the Truewide camera is the Hartlei camera with the exception of a focal plane shutter instead of the copal leaf shutter. Again it will be a tripod application only and it does not fit the hacker camera here.

4. Since the Hacker camera here cannot get to infinity focus it changed the f stop (light and depth of field not to mention optical performance since the Contax Carl Zeiss 85mm f/1.2 has floating elements so you cannot treat it like a large format lens).

5. The images of the flowers you see here were taken with lens that reached infinity focus so the absolute f stop was retained (no change in light, depth of field and optical performance). Furthermore, the captured images of the flowers were handheld and view through an optical prism finder. Don't take the flowers as a macro mode type of camera set up. In this setup, the camera is relevant to the original poster intention and style of shooting. Therefore the absolute f stop retention is POSSIBLE.

 

[Shashin]

5. The images of the flowers you see here were taken with lens that reached infinity focus so the absolute f stop was retained (no change in light, depth of field and optical performance). Furthermore, the captured images of the flowers were handheld and view through an optical prism finder. Don't take the flowers as a macro mode type of camera set up. In this setup, the camera is relevant to the original poster intention and style of shooting. Therefore the absolute f stop retention is POSSIBLE.

But the lens was not at infinity focus, the barrel might have indicated that, but that is because the lens was moved mechanically another way. Since the image and object planes are conjugate, meaning the position of these planes are not independent of each other, it means that the lens to image plane distance which effects the relative aperture and depth of field is the same as if you had focused to that point or used extension tubes or bellows.

Sorry, your idea is physically impossible.

The only way you could achieve no change in relative aperture is to optically change the lens by attaching a diopter.

 

[Vivek]

But the lens was not at infinity focus, the barrel might have indicated that, but that is because the lens was moved mechanically another way. Since the image and object planes are conjugate, meaning the position of these planes are not independent of each other, it means that the lens to image plane distance which effects the relative aperture and depth of field is the same as if you had focused to that point or used extension tubes or bellows.

Sorry, your idea is physically impossible.

The only way you could achieve no change in relative aperture is to optically change the lens by attaching a diopter.

Almost agree with all of that except the last part.

"a diopter" would not cut it. It has to be a custom adapter for a given lens.

 

[Shashin]

Almost agree with all of that except the last part.

"a diopter" would not cut it. It has to be a custom adapter for a given lens.

No, a diopter will not change lens to sensor distance problem, but the only way I know of to shoot closer without changing the effective f-number of the system is with a diopter/close-up lens. It won't help the lens hack though as you will still not be able to get the lens close enough to the image plane.

 

[Vivek]

Try different diopters for one lens and then find out if that (keeping the f number the same regardless of the magnification) is true or not. I have.

"a diopter" will not do. It has to be "the diopter".

 

[Shashin]

Try different diopters for one lens and then find out if that (keeping the f number the same regardless of the magnification) is true or not. I have.

"a diopter" will not do. It has to be "the diopter".

If you focus you lens to the infinity position and place a +1 diopter/closeup lens/filter on the lens, the lens will focus at 1m and the effective f-number will be the indicated f-number. Put a +3 diopter/closeup lens/filter and the lens will focus to .33m when the lens is focused to infinity and the effective f-number is the same as the indicated f-number. If you know another way to change the effective f-number without a change to the size of the exit pupil and lens to sensor distance, I would be interested to hear it.

 

[PSon]

But the lens was not at infinity focus, the barrel might have indicated that, but that is because the lens was moved mechanically another way. Since the image and object planes are conjugate, meaning the position of these planes are not independent of each other, it means that the lens to image plane distance which effects the relative aperture and depth of field is the same as if you had focused to that point or used extension tubes or bellows.

Sorry, your idea is physically impossible.

The only way you could achieve no change in relative aperture is to optically change the lens by attaching a diopter.

You only assumed that I had changed the optic mechanically. In fact my system never did and thus my lens work just like it was in the setting of the original system. No alteration was done. Thus, what you saw in those two images are the normal actual setting like the way the lens work on its native camera but with a medium format digital sensor behind it. The camera has an optical finder to shoot in the setting of the original poster.

 

[PSon]

85mm f/1.2 has an entrance pupil of 71mm
80mm f/1.8 has an entrance pupil of 44mm
110mm f/2 has an entrance pupil of 55mm
80mm f/2 has an entrance pupil of 40mm

The numbers don't lie.

The numbers do not lie but a set of numbers only represent one setting in real life. The number changes under a new setting. Take an example here, since the hacked camera from the original poster cannot reach infinity under normal setting, the image circle has increased to accommodate the bigger sensor size. If the lens was unchanged and use it like the native camera, the image circle would not be as big. Therefore, by using the larger format sensor with larger format lens such as the those mentioned by others and you quoted above can achieve the effect of narrow depth of field in spite of entrance pupil number.

 

[Vivek]

If you focus you lens to the infinity position and place a +1 diopter/closeup lens/filter on the lens, the lens will focus at 1m and the effective f-number will be the indicated f-number. Put a +3 diopter/closeup lens/filter and the lens will focus to .33m when the lens is focused to infinity and the effective f-number is the same as the indicated f-number.

That is what I meant by "a diopter won't cut it". It has to be a specific diopter for a given magnification.

I have no clue what Pham is trying to say but the claim that nothing changed and the effective aperture was the same with higher magnification does not happen.

 

[Shashin]

You only assumed that I had changed the optic mechanically. In fact my system never did and thus my lens work just like it was in the setting of the original system. No alteration was done. Thus, what you saw in those two images are the normal actual setting like the way the lens work on its native camera but with a medium format digital sensor behind it. The camera has an optical finder to shoot in the setting of the original poster.

Sorry, my mistake. I thought you were focusing on the flowers AT the infinity position.

 

[PSon]

That is what I meant by "a diopter won't cut it". It has to be a specific diopter for a given magnification.

I have no clue what Pham is trying to say but the claim that nothing changed and the effective aperture was the same with higher magnification does not happen.

There is no magnification on my system. Some of the 35mm format lens have big enough image circle to accommodate the bigger sensor. If a lens has a big enough image circle it can accommodate a bigger sensor without an sort of magnification needed whether through an extension tube or a diopter.

 

[Vivek]

I see how the confusion came in to this thread.

 

[Shashin]

The numbers do not lie but a set of numbers only represent one setting in real life. The number changes under a new setting. Take an example here, since the hacked camera from the original poster cannot reach infinity under normal setting, the image circle has increased to accommodate the bigger sensor size. If the lens was unchanged and use it like the native camera, the image circle would not be as big. Therefore, by using the larger format sensor with larger format lens such as the those mentioned by others and you quoted above can achieve the effect of narrow depth of field in spite of entrance pupil number.

It would not make any difference, the 70mm entrance pupil will always result in a shallower DoF compared to the others--image circle has nothing to do with it. Larger sensors increase DoF with a given focal length and so that is not going to help with the other lenses. You would need to put the other lenses on a much smaller format in order to to beat the 85mm. And being able to focus further away will not decrease DoF.

No, the numbers do not lie in this case, the 85mm f/1.2 is going to have shallower DoF as the entrance pupil is nearly twice the diameter. This is not a surprising result. Especially since this lens is on a MF camera. The other lenses will simply not compete here.

 

[Shashin]

I see how the confusion came in to this thread.

i am thinking of taking up knitting...

Or maybe drinking...

:chug:

 

[PSon]

It would not make any difference, the 70mm entrance pupil will always result in a shallower DoF compared to the others--image circle has nothing to do with it. Larger sensors increase DoF with a given focal length and so that is not going to help with the other lenses. You would need to put the other lenses on a much smaller format in order to to beat the 85mm. And being able to focus further away will not decrease DoF.

No, the numbers do not lie in this case, the 85mm f/1.2 is going to have shallower DoF as the entrance pupil is nearly twice the diameter. This is not a surprising result. Especially since this lens is on a MF camera. The other lenses will simply not compete here.

Shashin, I would agree with you if the 85mm F1.2 has a big enough image circle to accommodate the bigger sensor under the native setting. In this case the lens was used like you would with an extension tube to increase the image circle. Thus you can take a slow lens and extended long enough you still get very shallow depth of field. Therefore, the numbers have to fit within the function of the setting. Also I disagree that by putting the other lens (1.9/80, 2.0/110 etc.) in a much smaller format will not decrease the depth of field but would increase the depth of field instead.

 

[Shashin]

Shashin, I would agree with you if the 85mm F1.2 has a big enough image circle to accommodate the bigger sensor under the native setting. In this case the lens was used like you would with an extension tube to increase the image circle. Thus you can take a slow lens and extended long enough you still get very shallow depth of field. Therefore, the numbers have to fit within the function of the setting. Also I disagree that by putting the other lens (1.9/80, 2.0/110 etc.) in a much smaller format will not decrease the depth of field but would increase the depth of field instead.

This lens focuses to 6m/18ft. This is hardly macro photography and the images show that. It is a fairly usual object distance for portraiture and so it will always have less DoF than the other lenses--moving the subject further than 6m away from the camera is not going to decrease DoF so how could the other lenses catch up?

With a given focal length, using a smaller format or cropping will decrease DoF. This is nothing new. The reason being that you magnify the image more to reach the final display size and therefore the criteria for the permissible circle of confusion, what is considered the smallest sharp point size, is smaller.

Given the parameters of the lens/camera, I do not see any of the other lenses being able to compete with an equivalent DoF. This is a unique camera and there is no way to imitate its look with a given image scale regarding DoF with the other lenses. As fine as the other lenses are, they just cannot get there.

 

[ondebanks]

You only assumed that I had changed the optic mechanically. In fact my system never did and thus my lens work just like it was in the setting of the original system. No alteration was done. Thus, what you saw in those two images are the normal actual setting like the way the lens work on its native camera but with a medium format digital sensor behind it. The camera has an optical finder to shoot in the setting of the original poster.

Pham,

I'm quite confused by your posts down through this thread. When referring to your own flower closeups, you said "Thus, what you saw in those two images are the normal actual setting like the way the lens work on its native camera but with a medium format digital sensor behind it." You seem to be saying that this is different to what Marko did with his 85/1.2, but it isn't. In his case, he also used "the normal actual setting like the way the lens work on its native camera but with a medium format digital sensor behind it." If he'd shot the same model from the same distance at the same f-stop with the same 85mm on its native 35mm camera, he'd have got the same result, merely cropped around the perimeter. There would be no difference in effective f-stop, entrance pupil, focal distance, DOF, bokeh or anything else.

I don't want to belittle Marko's achievement (because it's quite stunning), but it "merely" has been to use a larger portion of the image circle that the lens already had. There are no optical gymnastics here at all. The only pity is that he was unable to recess the lens deeply enough for it to reach infinity focus.

Ray

 

[SergeiR]

Re: 85mm f1.2 on medium format

Sergei, yes indeed! I'm also not sure what you mean by the extension rings. Drilling was necessary to bring the lens close enough to the sensor so I could get a usable focusing range.

Closer subject - we need lens out farther from sensor? So, depending on how close you really ever go it might be possible to just push lens a bit out, without damaging mirror or anything Just a thought. I mean with normal focal length its better to stay away anyway to avoid distortion. That also would sort out problem with 6m max distance.. Or not. Depends Need to think. Given min focusing on regular 85/1.4 to be about 3.5 meters.. there is got to be some slack

So if we take the lens "tail" out, and replace it with thinniest of extension rings, we should be able to add them slowly if we ever need to get closer, or remove them if we need to get farther.

Extension rings i am talking about - are set of 3 "auto macro extension rings" - cant remember how much they cost, but should be less than AFD body So only thing we would miss is mechanical converter from Contax (in your case) or Canon (if someone feel like trying Canon 85/1.2 and see if it will be about same) to Mamiya 645 bayonet(mount)..

You did inspired me to play with few old petzvals i had laying about (got 2 projection ones, that wont cover 4x5) - their focal length is 260 and 150.. Looked like straightforward stuff.. But i didnt like picture i was getting (not enough corners to get actual swirl ) , so i took it apart.