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Thread: TLR DoF DOA

  1. #11
    FrankB's Avatar
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    Hi Marco,

    In 35mm terms, I generally work as you suggest.

    However, the depth-of-field in 6x6 with a standard (80mm) lens is considerably shorter than in 35mm with a standard (50mm) lens. With the 180mm Mamiya lens the DoF is *much* shorter than I'm used to! This, and the inability to check, is repeatedly tripping me up.

    For landscape work I am quite often finding that I haven't allowed a wide enough aperture for my composition and either the foreground or the background is soft. In another case I wanted selective DoF for a contre-jour dewy spider-webbed cross in a graveyard. When I check the neg afterwards I find that one side of the cross is sharp as a tack whilst the other is softer than I feel I can get away with, even at 10x8. (I'm currently looking at the possibility of doing this with a paper interneg to give the whole thing a softer, more textured feel... but I may well be in "sow's ear" territory! )

    I find the distance scales on the C330S very imprecise and (in my inexperienced hands) useless. Others may (and apparently do) find differently. I'm not very good at guessing distances. Others may be (and apparently are) better.

    The idea of a laser rangefinder may well be overkill, but on the other hand may speed my learning process i.e. "The hyperfocal near point for this lens at this aperture is *this* much which makes it about that rock *there*. The hyperfocal focussing distance is *this* much which makes it that mossy patch *there*. Job's a good 'un!"

    I did a quick search online and apparently I'm not the only one who thinks this method may have merit. Unfortunately the products the other chaps are using are only available on the other side of the pond and the ones over here are ridiculously pricey.

    In the meantime I'll keep practicing and bracket my apertures more. If it were easy it wouldn't be fun!

    All the best

    Frank
    The destination is important, but so is the journey

  2. #12

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    If you go on the Mamiya forums for TLRs, there are some very knolagable people there, Han and Graham the guys that wrote the book on these TLRs.

    I believe there are focusing aftermarket gizmos you can buy including some gaget that measures the distance the lens has moved off the body. Another I remember being marketed was a special knob with a scale on it like the Yashicas have.

    As many people here have mentioned, it's a matter of practice. Like your 35mm, you will pick up certain tricks to make life easy. If you are doing studio or controlled environment shooting, I sugest you put a ground glass on the film plane, make your focusing adjustments and make reference marks on your camera body so you can repeat the same on demand when you have it loaded with film.
    Anyone can make a Digital print, but only a photographer can make a photograph.

  3. #13

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    Well, Han Verhulst is actually writing the book.

    There were a few devices that attempted to compensate for the poor focus scales (mind you, no scale is as reliable as a good loupe on a large format camera, but I digress).

    One was an odd gadget that fitted in the flash shoe and incorporated something like a dial gauge. The anvil of the gauge pressed against a flange attached to the lens board of the camera. It gave very precise lens extension, provided the infinity point and the correct scale was used. Bear in mind that the extension of infinity focus varies with focal length with these cameras.

    Then there were two replacement focus knobs. One was just oversize, which makes finer adjustments easier. The other was internally geared and used a scale to give measurements.

    Best of luck finding any of these.

    The C33 scale was made up of a plate mounted alongside the bellows with a set of curved lines scribed on it. These lines read off against a vertical scale on the front of the camera body. Because the horizontal motion of extending the lens was enhanced by the vertical scale - more actual travel - it was potentially more accurate.

    The limited maximum apertures of the lenses count against you, too. The 180mm f4.5 has a DOF (from my own tables) of about 3.5 feet wide open at 30 feet. So your visual focus error is likely to be around +/- 1 ft.

    Stop-down depth of field preview on small and medium format has some value down to maybe f8 for me. Anything beyond that and you need a good screen, a darkcloth, and a magnifier.

    Depth of field _in practice_ is a fuzzy issue, more often than not. Experience in applying DoF tables is really useful.
    I feel, therefore I photograph.

  4. #14
    DBP
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    Quote Originally Posted by FrankB
    I may look into getting a laser rangefinder (although these are pricey in the UK)
    Before you go off and spend real money on double checking focus, why not pick up an old-fashioned rangefinder like item 7623982731 on e*b*a*y. They tend to be really cheap and quite accurate.

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