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Thread: how to get critical focus in the corners when using movements?

  1. #1

    how to get critical focus in the corners when using movements?

    I am worried that I am not getting the best focus when using the groundglass with and without movements. I use a loupe to check the corners for sharpness, but I can only check one at a time.. I get one corner in critical focus, then I check the next corner. But how can I verify that a second corner cannot be any sharper without throwing off the focus of the first?

    Perhaps I need to attune my 'sharpness memory'? Does ths get easier with experience?

  2. #2
    Steve Sherman's Avatar
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    how to get critical focus in the corners when using movements?

    If all you are photographing is the landscape don't get caught up in the advertisements you see for view camera movements. The actual off standard corrections you make are small. It is only in very close up work that the camera begins to really look off standard. Also, the shorter the lens the less the movement appears.

    To make things easier for myself, I try to decide what shape my composition is. If the shape in anyway resembles a rectangle I would tilt the lens in the direction of the longest plane of that rectangle. Lastly, many times you actually focus on something in mid air. Like riding a bike, experience is the best teacher.


    Real photographs are born wet !
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  3. #3

    how to get critical focus in the corners when using movements?

    Darin,

    Most of the times, we are looking at a very shallow plane in sharp focus, wich crosses the groundglass on whatever angle it's been determined by the movements we choose. Depth of field and small apertures are usually the only way to really make things come on sharp all around and it's difficult to evaluate this looking at the groundglass after closing some stops. So, I'd suggest you take a look on some technical articles you can find somewhere on this site, wich covers depth of field and related focusing problems when using movements. There's a lot of geometry involved, but the main idea is easy to grasp.

  4. #4

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    how to get critical focus in the corners when using movements?

    Look at your scene and determine where the plane of critical focus should be.
    Then select three points which fall in the plane and produce a good sized triangle on your ground glass. Pull these points into focus and you are all set. This will work in the vast majority of situations and is a good way to get the feel for the whole process.

  5. #5

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    how to get critical focus in the corners when using movements?

    Bruce Wehman puts it well. Check 3 points on the GG, but don't make any adjustments while moving from point to point! If you need a little back tilt, for instance, make the tilt and then re-check all 3 or 4 points. It helps if you have a bail lever---my 5x7 Wisner was giving me fits with soft corners, or a soft side, after seeing everything sharp with the loupe. The back springs were so strong that shoving a holder in usually moved the back enough to throw things off. If your camera doesn't have a bail lever, install one. It's easy to overdo the back tilt and make things loom unnaturally large in the foreground. See David Muench's books for examples of well-done tilts and swings. (Too bad he doesn't illustrate his technique anywhere...)

  6. #6

    how to get critical focus in the corners when using movements?

    Ah, Bruces technique does sound like a good solution. I am anxious to try it out now!

  7. #7

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    how to get critical focus in the corners when using movements?

    One possibility is that in the default positions, the two standards may not be quite parallel. Often there is some play in the detents, and there can be enough a swing so that the plane of exact focus in not parallel to the film plane. Usually, that would be taken care through depth of field by stopping down, but if you are stopping down as little as you can consistent with your DOF needs, such a slight swing might be visible.

    By use of a level it is possible to get both standards vertically parallel, but that won't work with horizontal parallelism. You can try measuring the distances between the standards on either side with a mm scale, but that may not be accurate enough to detect a small swing. But it should be apparent on the gg, and you may be able to correct it by adjustments within the play the detents allow. If that doesn't work, you may have to move out of the detents.

    A good recommendation, which I don't always follow myself, is never to assume anything. Always check as best you can that the standards are set properly.

  8. #8

    how to get critical focus in the corners when using movements?

    I would add slightly to Bruces comments. Remember that your depth of field is the same as you remember from your 35mm days - 1/3 in front of your film plane and 2/3 behind it on an incline (assuming you are using a front tilt). Carefully consider this when selecting a focus plane. Second thing I learned about using movements is that there are shots where you need to rely solely upon stopping down because there is not a place in the potential photograph where a film plane can be satisfactorly placed. In these situations you get to know reciprocity on a first name basis. Make sure that your are square to your camera bed and to each standard

    In these situations I have found that if it is possible to stop down while observing the ground glass, you can see if stopping down will satisfactorly increase depth of field. If this does not work, the alternative is to select another composition and/or lens that will be more favorable to your objectives. Lastly, I printed out some hyperfocal tables for my favorite lenses from the Schneider website to use as reference when out in the field. After a while, I remembered enough of this data to not have to look it up.

    Cheers!

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