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Thread: Fine focus required?

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    Fine focus required?

    I am currently chatting with Mike of Walker Cameras, with regards to getting a Titan XL 5x4 for use with my newly-acquired scanning back (Thanks, Doug and Chris!).

    I was asking about appropriateness for digital, and the focusing problems people have in general, to which he said he always uses standard pitch focusing (2mm apparently), but he could fit a finer pitch focus if required.

    I presume the requirement for fine focus increases as a lens' focal length decreases, but at the same time you will be decreasing focus 'snap' for longer lenses?

    So my question (for all those with much more digital experience than myself!) is:
    Below what focal length do you think fine focus would be beneficial? And at what point do you think it may become a hindrance?

    My guess is that I'll be looking to cover focal lengths between 55-90mm, or maybe even 135mm at a push.

    Thanks,

    Graham.

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    Re: Fine focus required?

    With those focal lengths, I would say you probably might like finer focus...most view camera users on film use lenses from around 90mm to 210mm. Since you are biased to the wide angles, the finer pitch should give you a bit more control. But I am not familiar with the Titan XL -- is it the type of camera where you can just loosen the focus knob and slide it manually? I know my Ebony is like that...but anyway, I doubt you would have a problem with the standard focus pitch unless you are exclusively using likes like the 24mm and 35mm apo digitars.
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    Re: Fine focus required?

    Interesting question... shooting LF film my shortest lens is 47XL (on 4x5" 6x9cm 6x12cm), but then again I never use it wide open, f/8 is about the largest aperture I've used with that lens. My primary "small" LF camera (as opposed to the 8x10 monorail) is my Ebony SW23, which with 56x84 mm image format is similar to a scanning back, so focal lengths and focusing considerations are related (though not the same).

    Rather than talking to Walker about pitch, would you consider widening your search a bit? I'd recommend considering Ebony SW45 as an alternate choice - great precision in manufacturing, and the design allows for tightening up focusing to have a rail-like feel to it. It's also a great choice for very short focal length, I use the 47XL on a flat board with plenty of room for shifts and tilts. It should handle a 35 on a recessed board. Though I think it might require a larger budget than the Titan.

    (Update: I see now that the Titan XL is rather similar to SW45 in overall design.)

    Either way, you could ask the manufacturer to fit larger focusing knobs, that would certainly improve focusing precision.
    Last edited by Lars; 12th April 2009 at 00:45.
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    Re: Fine focus required?

    Quote Originally Posted by Stuart Richardson View Post
    -- is it the type of camera where you can just loosen the focus knob and slide it manually?
    To be honest, I don't have a clue

    Quote Originally Posted by Lars Vinberg
    I see now that the Titan XL is rather similar to SW45 in overall design.
    Yes, now I check they are very similar. It looks as though the Walker is half way between an RSW and SW45; but not as pretty!

    Quote Originally Posted by Lars Vinberg
    Either way, you could ask the manufacturer to fit larger focusing knobs
    Now why didn't I think of that? Funny how the simpler answers often pass me by...

    Another option I have come up with -- again, feel free to comment -- is to have a standard rack on the front bed, and a fine one on the rear. Does that seem a fair compromise?

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    Senior Member Lars's Avatar
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    Re: Fine focus required?

    Quote Originally Posted by shakeshuck View Post
    Another option I have come up with -- again, feel free to comment -- is to have a standard rack on the front bed, and a fine one on the rear. Does that seem a fair compromise?
    Absolutely - now why didn't I think of that Make a rough setting with the front then fine tune the rear.
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    Rick Moore
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    Re: Fine focus required?

    Quote Originally Posted by shakeshuck View Post
    Another option I have come up with -- again, feel free to comment -- is to have a standard rack on the front bed, and a fine one on the rear. Does that seem a fair compromise?
    Some view cameras, such as the Sinar C, come standard with much finer control on the rear standard than on the front.

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    Re: Fine focus required?

    i'm using an arca swiss Fline 69, with the last arca screen.
    I can focus without problem with my 45... the 35 becomes a problem... but, it's not just a question of finer control, but also details visible on the ground glass... when i'm using live view, i can focus !
    The other trouble, is to make shure that the standard remains // !
    For finer focusing, with some lenses and camera, you can also mount the lens on a helicall mount... even with a LF camera... but with shorter lenses, you won't have the space to do it !

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    Re: Fine focus required?

    One word of advice for achieving accurate focus with short lenses on GGs: get an 8x loupe or larger. Okay, that was 6 words.
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    Senior Member routlaw's Avatar
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    Re: Fine focus required?

    Quote Originally Posted by shakeshuck View Post
    I am currently chatting with Mike of Walker Cameras, with regards to getting a Titan XL 5x4 for use with my newly-acquired scanning back (Thanks, Doug and Chris!).

    I was asking about appropriateness for digital, and the focusing problems people have in general, to which he said he always uses standard pitch focusing (2mm apparently), but he could fit a finer pitch focus if required.

    I presume the requirement for fine focus increases as a lens' focal length decreases, but at the same time you will be decreasing focus 'snap' for longer lenses?

    So my question (for all those with much more digital experience than myself!) is:
    Below what focal length do you think fine focus would be beneficial? And at what point do you think it may become a hindrance?

    My guess is that I'll be looking to cover focal lengths between 55-90mm, or maybe even 135mm at a push.

    Thanks,

    Graham.
    Graham

    Couple of thoughts here, based upon my own experience with using the BL in the field, but with a Zone VI circa late 90's.

    Of more importance than focus pitch is to know whether or not the Walker bellows that will allow a 55 mm lens does not leak infra red. This is a very serious issue you have to contend with because the infra red blocking filter is not on the sensor rather its at the lens. Often soft bellows that will allow for any movements with wide angles will leak infra red. I am not familiar with the walker but the Ebony universal bellows is famous for this as are some older Linhof and a few other bellows.

    Back to focusing, my Zone Vi is probably more crude in focusing than either of the camera's mentioned so far and at least to 90 mm it has never been a problem. In other words I am inclined to think it will not be a problem for you either. Once again of more importance regardless of which camera you go with make sure the scan back focusing plane is a perfect match to the calculated film plane. This has been discussed widely on the BL forums in the past, some cameras precise focus does not match the ground glass. We are only talking a mm or perhaps half that distance but it can cause problems. My own Cambo ULtima is one of them. Lay a large ruler/yardstick out on a table at about a 45 plane find an arbitrary POF, make a prescan and see if they line up precisely and predictably. If you don't get a predictable focus you have a much bigger problem than focus pitch at the knob. Its fairly easy to contend with in a studio environment but a different ball game in the field.

    Also invest in or make the best bright screen you can acquire. This will be way more helpful than 2 mm focus pitch.

    Hope this helps.

    Rob

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    Re: Fine focus required?

    Thanks for these updates, guys.

    I hadn't even considered the fact that the bellows wouldn't be IR tight.

    My first outing to test the kit properly was an attempt at a church interior, and was a complete disaster. With low light levels and mixed lighting (I didn't take any of my own) I kept getting odd and unpredictable colour shifts that I still don't know the cause of. It could have been a low laptop battery (I have been warned of this), or, as you say, stray IR. Now I know to look for it I'll keep my eye out.
    I was using a Horseman monorail that I've had for twenty years or so; even though it's had little use, the wide bellows could indeed be suspect.

    Thanks,

    Graham.

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