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Thread: 85mm f1.2 on Medium Format

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    85mm f1.2 on Medium Format

    Zeiss 50 Jahre 85mm f1.2 lens on a Mamiya 645AFD body with a digital back.

    From start to finish it is a long story but to cut it short, when I started this project I had no idea if this would work at all and if, to what extent. With the Zeiss being rare and pricey, I certainly didn't want to destroy it in the process! But I had no choice, not trying was not an option. I dismantled the rear portion of the lens to make it slimmer, followed by substantial drilling into the Mamiya body to make room for the lens. I also needed to shave the mirror by maybe 2-3cm and remove a fair number of camera components that were in the way. Having done all that, it was then possible to bolt the lens to the camera from the rear. Finally, I had to adjust the focusing screen so focus would match what I'm seeing in the viewfinder.

    Function and limitations: Obviously it is not as pretty or as functional as a native lens. The invasive procedure means:
    - the lens is attached to the body permanently
    - you cannot stop down the lens.
    - there is no infinity focus. Max focusing distance is abut 6m
    - in the viewfinder the top quarter or so is blacked out because of the mirror shave
    - there is no focus assist light; I'm assuming its because I pulled the electronics out
    - metering works but its far from accurate. Best to shoot manual with a light meter or check histogram
    - focusing is close to guesswork at the longer distances but is surprisingly manageable closer in. I'm using a Maxwell matte focusing screen. It does help.
    - the mirror did get somewhat damaged during the modification and it is somewhat less reflective.
    - the image circle covers the whole Aptus22 chip

    Image quality (as I see it):
    - within the lenses designated image circle everything is pin sharp (its even possible to see moire) with a nice smooth rendering
    - the edges rapidly lose sharpness and seem to swirl the image around the center. I actually don't see this as a problem, considering my subject matter its more of a plus.
    - there is only a (very) small bit of purple fringing in contrasty light
    - bokeh is smooth and wonderful

    Photos taken with this available here: Zeiss 85mm f1.2

    cheers,
    Marko
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    Subscriber Member KurtKamka's Avatar
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    Re: 85mm f1.2 on medium format

    Love the ingenuity, Marko. And the images look great. That lens produces some of the best bokeh available and pairing it with a medium format sensor is a dream proposition for those who like to shoot fast.

    Kurt

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    Re: 85mm f1.2 on medium format

    You are a crazy person, in the best sense. The results looks great. What made you decide to go through all this effort, versus perhaps giving the 110/2 Planar a go? It seems to have a somewhat similar look...
    But like I said, very nice that you decided what you wanted to do, and just did it, regardless of practicality.
    My photos are here: http://www.stuartrichardson.com and more recent work here: http://stuartrichardson.tumblr.com/ Please have a look at my book!
    My lab is here: http://www.customphotolab.is and on facebook

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    Re: 85mm f1.2 on medium format

    Hm. Thanks. I wonder if its possible to just butcher one of 3 extension rings and use it as tail mount for 1.2. Pity that lens is so expensive that it overcomes desire to experiment a bit.

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    Re: 85mm f1.2 on medium format

    Very cool DIY project, it would interesting to see it compared to the Mamiya 80mm f/1.9.

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    Re: 85mm f1.2 on medium format

    i think i have to do something similar one day with my contax645 and canon ts-e 17mm

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    Re: 85mm f1.2 on medium format

    Superb results!

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    Re: 85mm f1.2 on medium format

    Quote Originally Posted by drevil View Post
    i think i have to do something similar one day with my contax645 and canon ts-e 17mm
    Ack! Please don't tear up a 645!

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    Re: 85mm f1.2 on medium format

    Oh my God, you are a genius!

    Great results btw, sort of a proprietary look!

    Let me know if you would consider renting the camera, seriously.

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    Senior Member ondebanks's Avatar
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    Re: 85mm f1.2 on medium format

    Very ambitious project, delighted that it worked for you. The results look great.

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    Re: 85mm f1.2 on medium format

    WOW, Just wow!!! Congratulations!

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    Re: 85mm f1.2 on medium format

    Wow what a positive response! Thank you all
    To answer some of the questions:
    Stuart, for me it was a very easy decision. The 110/2 has a wonderful reputation and I certainly would like to try one someday. However, the 85/1.2 is a full one and a half stops faster. Not just the DOF, also the added light gathering abilities have come in handy. I also prefer the normal focal length. And I already have the RZ 110/2.8.
    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.
    It would be interesting to compare to the Mamiya 80/1.9. Unfortunately I do not have this lens. I did a quick comparison test with the Canon 50/1.2 on my 5D. One closer in the other further out. Shot handheld so there are framing differences. What I see: The Canon is a very nice lens, but is clearly beaten by the Zeiss. It is still very sharp, and certainly better in the corners with less distortion, but the Zeiss has better bokeh, shallower DOF and noticeably less chromatic aberration. The Canon shots were cropped to 4:3.
    I also attached a 100% crop of 'City'. Grain was added in post.
    best,
    Marko
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    Re: 85mm f1.2 on Medium Format

    135mm format Zeiss lens on digital medium format sensor. In these cases, there were no light loss and no macro narrow depth of field exaggeration (absolute f stop retain).

    Last edited by PSon; 8th March 2012 at 13:53.

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    Re: 85mm f1.2 on Medium Format

    So great Marko... love it.
    It's something i'd have done...

    Cheers

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    Re: 85mm f1.2 on Medium Format

    Interesting project, seemingly impossible, but your determination paid off! Thanks for sharing. Would love to see some photos of the actual work done to the camera body to make this possible.

    You already answered why ... the extra stop and half of light, but like Stuart, I wondered if it could be that much better than the Mamiya 80 f/1.9 or Hassie/Rollei 110/2 or Rollei Schneider 80/2. The zeiss bokeh - chromatic doublets and hard edges with soft insides ... you either love it or you don't but no one can't say it doesn't have character.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by EH21 View Post
    ...I wondered if it could be that much better than the Mamiya 80 f/1.9 or Hassie/Rollei 110/2 or Rollei Schneider 80/2...
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    In these cases, there were no light loss and no macro narrow depth of field exaggeration (absolute f stop retain).
    Impossible.

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    Re: 85mm f1.2 on Medium Format

    Marko,

    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    Marko,

    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.
    The only other possibility I can think of is the Hartblei Cam. Sure, you could mount and focus the lens on a tech-cam and MFDB...but you have to have something with a shutter.

    Ray

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    Re: 85mm f1.2 on Medium Format

    Yeah, if Canon EOS lenses can be attached to a MFDB with a shutter in between, Contax should be very possible.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    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?

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    Senior Member PSon's Avatar
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    Re: 85mm f1.2 on Medium Format

    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    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".

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    I see how the confusion came in to this thread.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    I see how the confusion came in to this thread.
    i am thinking of taking up knitting...

    Or maybe drinking...


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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    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.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    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

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    Re: 85mm f1.2 on medium format

    Quote Originally Posted by MarkoRepse View Post
    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.
    Last edited by SergeiR; 9th March 2012 at 11:15.

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    Re: 85mm f1.2 on Medium Format

    Apologies to anyone if this has already been discussed

    Pham is correct about the effective fstop. Since I cannot focus at infinity it is as if I am using a thin extension tube on its native camera (but with a bigger sensor). Moving the lens further away reduces the effective aperture. However, to get to infinity requires moving the lens closer by a few millimeters at most. Unfortunately this is not possible. But in practice this amount is negligible and I very much doubt anyone would notice any difference. In any case, I am superbly happy with the results. I do not see how theoretical perfection would improve my photography.

    Quote Originally Posted by Vivek View Post
    Marko,
    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.
    Vivek, maybe I overstated the difficulty of focusing. It is indeed difficult to focus at 6m, however the same can be said for any lens. I will probably get a magnifier as it should help. Closer in and with good light its not a problem. I actually shot the whole 'city' series handheld. Practically impossible with the Hartblei.

    Sergei, if I understand you correctly, unfortunately I do not think that would work. Because if I move the lens by 2-3mm further away than it is currently, the max focusing distance drops to maybe 1m. I had it like this for a while in an earlier stage and it was not very useful. If you succeed with your petzvals, do let us know

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by MarkoRepse View Post
    Apologies to anyone if this has already been discussed

    Pham is correct about the effective fstop. Since I cannot focus at infinity it is as if I am using a thin extension tube on its native camera (but with a bigger sensor). Moving the lens further away reduces the effective aperture. However, to get to infinity requires moving the lens closer by a few millimeters at most. Unfortunately this is not possible. But in practice this amount is negligible and I very much doubt anyone would notice any difference. In any case, I am superbly happy with the results. I do not see how theoretical perfection would improve my photography.
    Actually, focusing at 6m would be the same whether the lens could reach infinity or not, so it is really not saying much as most lenses can focus at 6m and would have the same relative change. The increase of the effective aperture at the distances you work at are insignificant at the object distance you are working at--that is true for all lenses. Do you actually compensate for exposure when focusing to say 3m?

    But it is a wonderful camera for what it does.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by MarkoRepse View Post
    Sergei, if I understand you correctly, unfortunately I do not think that would work. Because if I move the lens by 2-3mm further away than it is currently, the max focusing distance drops to maybe 1m. I had it like this for a while in an earlier stage and it was not very useful. If you succeed with your petzvals, do let us know
    Yeah. its kinda tricky. As with petzvals - its just easier for me to get it all on 4x5 No real reason to play with 645 body (although - i do have one to spare )

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.
    There are several things need to be defined here:
    1) Depth of field is not totally dependent solely on entrance pupil. Take a couple examples (more than two), a) it depends how well the lens is corrected for colors and b) the in general max-center resolution fall off from the center of the image circle. These are two examples of what other elements could effect the depth of field. Thus the entrance pupil alone cannot determine the total outcome of depth of field.

    2) Since the ultimate goal is to achieve shallow depth of field, the focal length can be varied to the availability of lens with speed and size of image circle. For example the Kodak Aero 178mm f2.5 lens on the Crown or Speed Graphic 4x5 will result in thin depth of field.
    http://marktucker.wordpress.com/2011/01/21/homemade/

    3) By putting the lens onto smaller format does not necessary translate to thinner depth of field since the crop factor (using primarily the sharpest part of the lens image circle) to increase the focal length versus the native fall off of a full image circle of the lens. This is why folks prefer bigger full frame looks. An example is the Zeiss Sonnar 1.8/135 on the Sony A77 is about 202mm f/1.8. However the depth of field is greater than a Canon 1.8/200 EF lens on a full frame 5D. Numbers has to be adjust accordingly in the function.
    Last edited by PSon; 9th March 2012 at 12:58.

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    Re: 85mm f1.2 on Medium Format

    I would love something like this. I wonder about the focusing though as I know how hard it is just focusing the 110mm f2. Would be ideal if this could be done on a camera with reliable focus confirmation.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Pham Minh Son View Post
    There are several things need to be defined here:
    1) Depth of field is not totally dependent solely on entrance pupil. Take two examples (more than two) it depends how well the lens is corrected for colors and the in general max-center resolution fall off from the center of the image circle. These are two examples of what other elements could effect the depth of field. Thus the entrance pupil alone cannot determine the total outcome of depth of field.
    Lens aberrations have nothing to do with DoF. Basically, DoF can be defined with two criteria, the angular size of the entrance pupil and the permissible circle of confusion. The first is how large the angular size of the entrance pupil would be from the subject which defines how fast things fall out of focus. The permissible circle of confusion defines sharpness which is solely a factor of format size.

    You can also define DoF based on object distance, aperture, and focal length, but those are really two sides of the same coin. You always need circle of confusion.

    2) Since the ultimate goal is to achieve shallow depth of field, the focal length can be varied to the availability of lens with speed and size of image circle. For example the Kodak Aero 178mm f2.5 lens on the Crown or Speed Graphic 4x5 will result in thin depth of field.
    Homemade Cameras, (carrying the torch). « Mark Tucker : Journal
    No one is doubting that lenses can have a narrow DoF. In fact, the AeroEktar has the same size entrance pupil as the 85mm f/1.2. The DoF will not be identical however because of the difference in format and therefore the permissible circle of confusion.

    The image circle per se has nothing to do with DoF. A 178mm f/2.5 lens with a larger image circle would have the same DoF on a 4x5 camera as the Kodak lens. And the Ektar on a 35mm camera would have even less DoF. The factor is the permissible circle of confusion for the formats.

    3) By putting the lens onto smaller format does not necessary translate to thinner depth of field since the crop factor (using primarily the sharpest part of the lens image circle) to increase the focal length versus the native fall off of a full image circle of the lens. This is why folks prefer bigger full frame looks. An example is the Zeiss Sonnar 1.8/135 on the Sony A77 is about 202mm f/1.8. However the depth of field is greater than a Canon 1.8/200 EF lens on a full frame 5D. Numbers has to be adjust accordingly in the function.
    What I am saying is if you put a specific lens with a specific focal length on two cameras with different format sizes, the camera with the smaller format will produce less DoF with that lens at a given aperture.

    Your example is showing changes to two parameters at the same time. All you have said is a 135mm f/1.8 lens (with a 75mm entrance pupil) on a APS camera has a greater DoF that a 200mm f1.8 lens (with a 111mm entrance pupil) on a 35mm camera. As would would expect from a lens with a smaller entrance pupil and less magnification. So while the DoF changes proportionally with the format crop factor (permissible circle of confusion), the DoF also changes with the reciprocal of the focal length squared. So in this case, the longer focal length lens on the 35mm has less DoF--it also has a greater entrance pupil.

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    Re: 85mm f1.2 on Medium Format

    Pham, here is an online pdf by Zeiss about Bokeh, but also covers DoF very well.

    http://www.zeiss.com/c12567a8003b8b6f/embedtitelintern/cln_35_bokeh_en/$file/cln35_bokeh_en.pdf

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    Re: 85mm f1.2 on Medium Format

    *shudders* can we please not go into that whole discussion on how and what affects DOF

    It was such a nice DIY thread..
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    Re: 85mm f1.2 on Medium Format

    Sergei, One of these days I am going to put my 98mm f/1 Wild Heerbrugg on MFDB to make photos.

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    Re: 85mm f1.2 on Medium Format

    Got to admit - never heard of it before.. (thus - googled) Wild Heerbrugg Falconar 1.4/98mm ?
    That would be interesting to see, as it should be just past "normal" i.e short tele- might be perfect for portraits if it covers enough

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