Graduated center ND filter for Mamiya 7 lenses?

Discussion in 'Medium Format Cameras and Accessories' started by StoneNYC, Oct 19, 2013.

  1. StoneNYC

    StoneNYC Subscriber

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    Does anyone use Graduated center ND filter for Mamiya 7 lenses?

    I may be using the wrong term but I know they make them for certain LF cameras but I've noticed a LOT of vignetting on the Mamiya 7 lenses, and most of the time I like it, but sometimes I don't want the effect like in panoramically it images I want the detail in the corners.

    Anyone?


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  2. BennehBoy

    BennehBoy Member

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    I've never seen one for any of the 7 lenses, they'd have to be manufactured specific to each lens and would likely only be effective at certain (wider) apertures before ending up with a reverse vignette.

    Might be simpler to stop down? Or are you seeing problems at small apertures. Which lens(es) by the way?

    Can't say I ever noticed a problem with the 65 or 80.
     
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  3. David Allen

    David Allen Member

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    I also have no problems with the 65mm lens.

    Can you post some examples?

    David
    www.dsallen.de
     
  4. StoneNYC

    StoneNYC Subscriber

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    Hmm I think my 43mm has it worst? I'm on my phone and only have a few examples accessible

    ImageUploadedByTapatalk1382218206.666829.jpg
    ImageUploadedByTapatalk1382218636.168163.jpg

    These aren't terrible but another example

    ImageUploadedByTapatalk1382218772.727752.jpg
    ImageUploadedByTapatalk1382218842.351746.jpg

    It seems more noticeable in darker scenes or darker parts of a scene.

    I may also have slightly corrected for this already in these images so it might have been stronger before, but I could have sworn it was not just in the 43mm but also the 65mm and MAYBE 150mm (that's all I have).



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  5. Dan Fromm

    Dan Fromm Member

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    Stone, I just did the calculations. On 6x7 (90 mm diagonal), a 43 mm lens will be down between 1 2/3 (cos^3) and a hair over 2 (cos^4) in the corners. A 65, around 1 stop down, and 150 < 1/4 stop. If y'r 150 vignettes perceptibly the reason has to be mechanical, perhaps a filter in a really thick ring.

    I have no idea what size the M7 43 mm's filter threads are. You're in NYC, should be able to rent a center filter for a 47 SA or 45 AG. These come in a couple of sizes, if one fits your lens rent it and see what it does for you. These beasties are all a little approximate.
     
  6. cliveh

    cliveh Subscriber

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    Why would you want to use such a gimmick?

    Sent by an old out of date computer.
     
  7. StoneNYC

    StoneNYC Subscriber

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    Well certainly it happens with and without filter rings so that's not the issue.

    Also I don't live in NYC I live in CT (it's easy to make that mistake obviously I understand).

    I guess I'll just deal with it, many times it's nice, just sometimes on chromes especially it's stronger.

    I also don't understand your math, and I mean that I couldn't handle trigonometry at all and I'm not even sure what you said really means, can you dummy it down? Why would the lens mm change the "stop"?

    Thanks!


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  8. StoneNYC

    StoneNYC Subscriber

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    Lol, the same reason many LF shooters use them, to creat an evenly exposed image...

    Sent from a phone with probably more technology than your computer :wink:


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  9. ROL

    ROL Member

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    The graduated center filter was a big (expensive) deal for "professional" color slide shooters for the M7 series' 43mm lens, at one time. I've used the lens without for years, both on chromes and B/W. I've never personally had a need for it. Although I don't shoot much color, I've had nothing but good results without. Likewise, of the thousands of monochrome negatives I've made with the combination, I've never either noticed it, or was easily able to adjust in printing. The 43's lens hood might help a great deal, assuming you've got one. As per Dan's observations, I'd be more afraid of the filter's unspecific adulterations to light.

    BTW, I've also never used such a filter with LF, although the potential for uneven exposure with wide angle lenses is much greater. I always take care of it in printing.
     
  10. StoneNYC

    StoneNYC Subscriber

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    Interesting, I don't print (yet) optically and dislike having to do it digitally in post.

    Yea I only learned about center density filters after reading about the trouble with ultra wide LF lenses which is how I got the thought in the first place :smile:


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  11. Rafal Lukawiecki

    Rafal Lukawiecki Subscriber

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    Stone, I like your snow scene, very much.
     
  12. StoneNYC

    StoneNYC Subscriber

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    That's a huge complement, thank you!


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  13. MattKing

    MattKing Subscriber

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    Stone:

    As far as the trigonometry is concerned, think of it this way:

    With any lens, the light rays from the edges have much farther to travel than the ones from near the centre, so by the time the light from the edges reaches the film it is tired, so the edges are darker :wink::wink::wink:.

    Speaking slightly more seriously, it is just the nature of the optical realities.

    In general, the result is both natural and aesthetically pleasing, except when the shot is of something flat which we expect to be illuminated evenly - something like a wall.

    The desire to illuminate the scene evenly when the angle of view is quite wide probably comes from viewing to many photographs on TVs/monitors - they look quite natural on prints.