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Thread: Sinar db aperture

  1. #1

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    Sinar db aperture

    I've just received my first db mounted lens (g-claron 305mm) to use on my modified 6"x15" camera, and the aperture is a very strange shape.....not at all circular as I expected. Is this normal, or is it faulty?

    Click image for larger version. 

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    Thanks
    Bruce
    Last edited by brucep; 5-Jun-2015 at 06:06. Reason: hadn't subscribed to notificationa

  2. #2

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    Re: Sinar db aperture

    Normal.

  3. #3

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    Re: Sinar db aperture

    I always believed the closest to a circle the aperture was the better the out of focus highlights would be. Does the shape of the aperture have any detrimental effect on the bokeh?

    Bruce

  4. #4

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    Re: Sinar db aperture

    Bruce - unless I'm really out of kilter here, I wouldn't have thought that there would be much 'bokeh' with a G-Claron

    rgds
    andrew

  5. #5

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    Re: Sinar db aperture

    Quote Originally Posted by Andrew Plume View Post
    Bruce - unless I'm really out of kilter here, I wouldn't have thought that there would be much 'bokeh' with a G-Claron

    rgds
    andrew
    Sorry, that was a general question, rather than specific to the g-claron. I was thinking about possible other lenses.

    Bruce

  6. #6

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    Re: Sinar db aperture

    The influence of aperture shape on blur rendition is most noticeable when the subject contains specular highlights (or conversely dark spots over a white background). With a pentagonal aperture, we get pentagonal stars. With a quasi-pentagonal aperture - as shown in your photo - we get quasi-pentagonal stars.

    When no strong tonal transitions occur in the subject... opinions vary. You might find this article interesting: Large Format Bokeh Test. At f/11, the difference between lenses of different design (and shutter blades) is pretty hard to spot.

    Whatever the opinions of others, in the end it comes down to your personal taste, just like all the other factors including choice of lens, film, developer, camera, tripod, light meter, etc. If you can see the difference and it bothers you, then it's a substantial difference. If not, it's not.

    That being said, many would prefer a perfectly round aperture over a geometric one, all things being equal - except for those who think that polygonal blur looks "cool", "retro", "edgy", etc.

    Modern manufacturers seem to be listening to customer preference in this regard, since new lenses tend to boast curved aperture blades and reviewers will point it out when they do.
    Last edited by Ken Lee; 5-Jun-2015 at 12:57.

  7. #7

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    Re: Sinar db aperture

    Bruce,

    Original Sinar mounted DB lenses have usually only the diaphragm of the DB lens mount plate. What's noted in the Sinar literature is, when using non-originally mounted DB lenses in Sinar DB aperture units AND Sinar Copal shutter, the Sinar shutter - having a linkage to the DB board - have to be used wide open, and the aperture set by the lens diaphragm itself. I have both types and that's what I do: if the lens has a great number of diaphragm blades - at least greater then the DB mount plate - I use this, as I expect to have a more creamy bokeh with a larger aperture blades. I am not sure if the blades on the DB mount can be used without the Sinar Copal shutter and my perception of this is not. So, it is not possible, for my understanding, to use a originally DB mounted lens with a curtain shutter as the Graflex Speed Graphic, for instance. You can only use the aperture blades of a DB lens board with a Sinar Copal shutter. Corrections are welcome, as usual.

    HTH,

    Renato

  8. #8

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    Re: Sinar db aperture

    Thanks everyone for the answers

  9. #9
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    Re: Sinar db aperture

    Quote Originally Posted by brucep View Post
    I've just received my first db mounted lens (g-claron 305mm) to use on my modified 6"x15" camera, and the aperture is a very strange shape.....not at all circular as I expected. Is this normal, or is it faulty?

    Click image for larger version. 

Name:	WP_20150604_20_45_45_Pro[1].jpg 
Views:	37 
Size:	59.8 KB 
ID:	134918

    Thanks
    Bruce
    You think that looks off center or what? Looks pretty good from the picture.

  10. #10

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    Re: Sinar db aperture

    Worth noting is what the original market for Sinar DB mounted lenses and Sinar shutters (both mechanical Copal & Digital electronic). This Sinar shutter and DB lens system was intended and often used by commercial studio photographers burning hundreds of sheets of film per day. This was common when producing images for catalogs and such back in the day. Under these conditions, working aperture for 4x5 was often f16 to f45 with camera movement as required. Out of focus rendition and related at apertures larger than f8 was not common. At their working apertures (f16 to f45 and smaller), the shape of the DB lens mount worked well. Having auto stop down aperture and closing of the shutter upon film holder insertion makes burning a few hundred sheets of film each day a lot less work and reduces the problem of remembering to stop down the lens.


    It is in more recent times that noncommercial photographers have taken on using the Sinar shutter for barrel & DB lenses for a host of reasons. IMO, given the size-weight-bulk and such related to using DB lenses, it's a mixed bag of good and bad. If one is interested in using wide aperture barrel lenses (f8 and larger) and wanting a specific out of focus rendition look of a round aperture, older barrel lenses are the way to go.



    Bernice

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