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Thread: 85mm f1.2 on Medium Format

  1. #51
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    Re: 85mm f1.2 on Medium Format

    I think the Falconer lens is corrected for particular parts of he spectrum and may not be great with white light--lots of CA. I think on the aerial camera, the lens was shimmed for certain wavelengths like red, yellow, blue, etc. But I have never seen one in the flesh.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    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.
    What Son is pointing out here is that the permissible circle of confusion is indeed influenced by actual lens designs that take certain corrections into account in order to achieve higher contrast and resolution. If this were not the case, then there would be no difference between a Zeiss lens versus a Leica lens versus a Canon lens or any other of the same focal length even if they had similar entrance pupils. However, we all know that this is far from true. Sharper lenses allow smaller circles of confusion and we can see this difference.

    Basically, the MTF/OTF of a lens does affect the DOF. For example, a 85mm lens with almost perfect MTF characteristics (100% transmission) cannot have the same DOF as another 85mm lens with extremely poor MTF, even with a common entrance pupil. In fact, in the extreme limit of a hypothetical lens that is so terrible that it has 0% MTF, such a lens cannot possibly have any DOF.

    Son merely points out here that field curvature and this variation of MTF from center frame to edge will also vary among lens designs of a given focal length. A lens with very quick fall-off from center will exhibit shallower depth of field compared to a lens of the same focal length (and entrance pupil) that is "flat" and does not have such fall-off.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by SergeiR View Post
    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
    Not that one. A 9.8cm f/1 Reconar (really f/1.0!).

    See: http://forum.getdpi.com/forum/sony/3...s-nex-7-a.html

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    Re: 85mm f1.2 on Medium Format

    David, which of these lenses under discussion would have such horrible MTF where DoF is impacted:

    Mamiya 80 f/1.9 or Hassie/Rollei 110/2 or Rollei Schneider 80/2.
    I still say that none of those lenses will produce less DoF than the 85 f/1.2 simply because of the difference in entrance pupil. That is the discussion.

    Also, the ability to produce smaller circles of confusion does not change DoF--the permissible circle of confusion is just the value used to calculate DoF and can be set as you like. Lens aberrations are neither here nor there in this discussion.
    Last edited by Shashin; 10th March 2012 at 07:20.

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    Re: 85mm f1.2 on Medium Format

    I will be on the Canon CPS Roadshow 2012 starting next tuesday in Berlin.
    I will have an Aptus II 12 from Yair for the show to put on the HCam and I will take a look about the Canon 1,2 85mm, I think I already did this before, but the Image circle was not big enough. What I have used a lot was my Contax Planar 1,4/85mm (also the new IR version) and this one filled the large chip easily.
    And- we have a Handgrip for the HCam-B1, it´s made by Novoflex and especially the B1i or B1v are certainly usable with an additional finder.

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    because photography is more than technology - and " as we have done this all the time "
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    Re: 85mm f1.2 on Medium Format

    Shashin,

    You are not making any logical sense here. Previously, in your post #46 of this thread you say,

    Quote Originally Posted by Shashin View Post
    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.
    Then, in your post #54 of this thread you say,

    Quote Originally Posted by Shashin View Post
    Also, the ability to produce smaller circles of confusion does not change DoF--the permissible circle of confusion is just the value used to calculate DoF and can be set as you like. Lens aberrations are neither here nor there in this discussion.
    This is a logical contradiction of your previous post.

    I (and most photographers) maintain that circles of confusion have EVERYTHING to do with DoF.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    Shashin,

    You are not making any logical sense here. Previously, in your post #46 of this thread you say,



    Then, in your post #54 of this thread you say,



    This is a logical contradiction of your previous post.

    I (and most photographers) maintain that circles of confusion have EVERYTHING to do with DoF.
    David, I don't know why saying aberrations are not a factor in DoF and then saying that have nothing to do with DoF is a contradiction.

    Also please read what I write rather than imagining what I write. I state rather clearly that DoF is dependent on circles of confusion.

    Before I leave this conversation, the term "permissible circle of confusion" indicates the maximum spot size that is considered to be the limit of sharpness. This is a subjective numbers and manufacturers can use any permissible cycle of confusion they believe would give them the best description of DoF. And individual photographer can do the same. But when we look and an image and perceive DoF, we will set a natural limit based on vision. What does it matter how small the permissible circle of confusion is if it is smaller under the actual permissible circle of confusion? (Rhetorical question, BTW.)

    I posted a link to a Zeiss article. Please read that. It will help you understand this problem. I have already broken Sergie's command to stop talking about DoF. His wish is my command.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    David, I don't know why saying aberrations are not a factor in DoF and then saying that have nothing to do with DoF is a contradiction.

    Also please read what I write rather than imagining what I write. I state rather clearly that DoF is dependent on circles of confusion.
    In your previous post you also say that "circles of confusion does not change DoF". So, it makes no logical sense to say that and also maintain that "DoF is dependent on circles of confusion". This is a contradiction. Either circles of confusion change DoF or they don't.

    Lens aberrations do contribute to blur, which directly relates to circle of confusion. Again, a very soft lens will limit its depth of field compared to a very sharp lens. And, you cannot subjectively change the circle of confusion to make a soft lens any sharper. This is ultimately limited to how well the aberrations are controlled by the lens itself.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    In your previous post you also say that "circles of confusion does not change DoF". So, it makes no logical sense to say that and also maintain that "DoF is dependent on circles of confusion". This is a contradiction. Either circles of confusion change DoF or they don't.
    I am using the comparative "smaller." If the permissible CoC is X, than a CoC of X/2 is not going to change DoF.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Stefan Steib View Post
    I will be on the Canon CPS Roadshow 2012 starting next tuesday in Berlin.
    I will have an Aptus II 12 from Yair for the show to put on the HCam and I will take a look about the Canon 1,2 85mm, I think I already did this before, but the Image circle was not big enough. What I have used a lot was my Contax Planar 1,4/85mm (also the new IR version) and this one filled the large chip easily.
    And- we have a Handgrip for the HCam-B1, it´s made by Novoflex and especially the B1i or B1v are certainly usable with an additional finder.

    Regards
    Stefan
    Stefan, do you have any samples of the 85/1.4 shot at 1.4 you could share? I'm curious how it would compare to the 1.2 version. And the Canon as well when you have them.

    As for the DOF discussion, I prefer not to debate this, but my view is that the confusion comes from two ways you can look at DOF. DOF is caused by the bending of light. The first I will call absolute DOF, which is the result of just the bending of light and is a theoretical concept. In practice this determines how much the OOF areas blur. Then there is which I will call rendered DOF, and here we need to take into consideration also the system resolution, lens resolution, etc., as it essentially tells us how big the CoC is. Note that absolute DOF has a CoC of zero. So a better lens/sensor will let us "zoom in" more. This means that two different lenses with the same focal length and aperture will have identical absolute DOF, their rendered DOF can be different. I hope this has been clear enough.

    To finish on a more interesting note, I also added two photos from the 'city' series

    Square

    Street
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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    Lens aberrations do contribute to blur, which directly relates to circle of confusion. Again, a very soft lens will limit its depth of field compared to a very sharp lens. And, you cannot subjectively change the circle of confusion to make a soft lens any sharper. This is ultimately limited to how well the aberrations are controlled by the lens itself.
    Sergei is going to kill me. But the answer is no. You have a lens that is sharp or unsharp. How can you even determine DoF in an unsharp image?

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    I am using the comparative "smaller." If the permissible CoC is X, than a CoC of X/2 is not going to change DoF.
    This is simply not true.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    Sergei is going to kill me. But the answer is no. You have a lens that is sharp or unsharp. How can you even determine DoF in an unsharp image?
    A sharp lens will support a smaller circle of confusion than an unsharp one.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    This is simply not true.
    Actually, it is true. If the permissible CoC defines the DoF, then all the CoCs smaller than that does not change the DoF.

    I think you are confusing DoF with resolving power.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    A sharp lens will support a smaller circle of confusion than an unsharp one.
    Yes, but the unsharp lens has CoCs larger than the permissible CoC and so the unsharp image has no DoF that can be determined. So to even talk about DoF in an unsharp image is pointless.

    You really should read the document I linked to in a pervious post.

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    Re: 85mm f1.2 on Medium Format

    See (the middle of) my post above. I think the confusion comes from how you define DOF

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Shashin View Post
    Yes, but the unsharp lens has CoCs larger than the permissible CoC and so the unsharp image has no DoF that can be determined. So to even talk about DoF in an unsharp image is pointless.

    You really should read the document I linked to in a pervious post.
    First, no one is talking about an unsharp image here. A lens that is characterized as being "unsharp" is simply a statement that its MTF is not as high as a lens that can be characterized as "sharp". So, in the context of CoC and DoF, "sharp" and "unsharp" refer to relative MTF performance.

    I understand CoC and its relation to DoF. What you don't seem to understand is that lens aberrations and lens MTF/OTF performance do affect what can be used as a permissible CoC.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by MarkoRepse View Post
    See (the middle of) my post above. I think the confusion comes from how you define DOF
    I am using the standard technical definition. Which is really the only way you can define it.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    First, no one is talking about an unsharp image here.

    A sharp lens will support a smaller circle of confusion than an unsharp one.
    Well, if the lens is unsharp, the image from that lens must be unsharp. How else can you define unsharp>

    A lens that is characterized as being "unsharp" is simply a statement that its MTF is not as high as a lens that can be characterized as "sharp". So, in the context of CoC and DoF, "sharp" and "unsharp" refer to relative MTF performance.

    I understand CoC and its relation to DoF. What you don't seem to understand is that lens aberrations and lens MTF/OTF performance do affect what can be used as a permissible CoC.
    You are talking about contrast and how an image is rendered. This is not DoF.

    Since the permissible CoC is defined by the format size, the MTF is really not a factor. The MTF of a lens does not change no matter what format you use it with, the DoF will as the permissible CoC is different.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by David Klepacki View Post
    This is simply not true.

    +1

    (If anyone has a problem with that, I have two suggestions.

    1. Look up the actual origins of CoC in detail. Hints: There are a lot of variables. DoF are approximations based on a big list of assumptions.

    2. Better yet, use a camera and make some images.)

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by Vivek View Post
    +1

    (If anyone has a problem with that, I have two suggestions.

    1. Look up the actual origins of CoC in detail. Hints: There are a lot of variables. DoF are approximations based on a big list of assumptions.

    2. Better yet, use a camera and make some images.)
    So you are saying that the smallest CoC defines the DoF, not just the permissible CoC? I would suggest you look up the origins of CoC in detail.

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    Re: 85mm f1.2 on Medium Format

    Quote Originally Posted by MarkoRepse View Post
    Two more gems, Marko!
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