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Thread: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

  1. #1

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    Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Wondering if anyone has created spreadsheets for quick bellows extension guide. I shoot 4x5 using Schneider Super-Angulon 90/5.6 XL, Super-Symmar 150/5.6 XL, and Nikkor 300M/9.

    I usually do landscapes but now I want to shoot some details and textures at close range. I will probably start with the 150 XL and 300M so those are my priority.

    Edit: I’m thinking I will use the 150mm for starters on my 4x5. If you use an example of a closeup, please use 150mm
    Last edited by pchaplo; 16-Feb-2018 at 19:11. Reason: Using 150mm first
    Dallas Texas HABS / HAER / HALS Photography
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  2. #2

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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Why? It is pretty easy to just look at the gg. And what image ratios would you want it for?

  3. #3

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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Key magic formulas:

    extension = focal length *(magnification + 1)

    Extension is measured from the film plane to the lens' rear node. For most LF lenses the rear node is close to the diaphragm.

    Front node to subject distance = focal length *(magnification + 1)/magnification

    For most LF lenses the front node is close to the diaphragm.

    effective f/ number= f/ number set * (magnification + 1)

    You're going to need 600 mm extension to shoot a 300 mm lens at 1:1. Front node to subject distance will also be 600 mm. There are some subjects for which that much working distance is helpful, but in general you'd be better off using a shorter lens at 1:1.

  4. #4
    Drew Wiley
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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Today I used a little gadget from Calumet. It's a little plastic crosshair card you place in the scene, then you measure the width of it on your groundglass using a special plastic ruler marked in f-stop factors. Really portable and works for all lenses. Maybe someone else is making something like this now that Calumet is gone.

  5. #5

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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    (bellows extension) / (focal length) = extension factor

    This factor works just like a filter factor: Factor 2 equals one full stop of exposure compensation, factor 4 equals two full stops, factor 8 equals three full stops, etc.

  6. #6

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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Quote Originally Posted by Drew Wiley View Post
    Today I used a little gadget from Calumet. It's a little plastic crosshair card you place in the scene, then you measure the width of it on your groundglass using a special plastic ruler marked in f-stop factors. Really portable and works for all lenses. Maybe someone else is making something like this now that Calumet is gone.
    I have the same, mine is actually printed on paper and laminated. It's at work right now but if I happen to be reminded on this thread on Monday I could scan it and post pdf's somewhere for people to download.

  7. #7
    Tin Can's Avatar
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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    I use my 'Calumet Exposure Calculator' all the time as I do mostly studio experiments. I'm not using the 'work' word anymore, as I agree with Maynard G. Krebs. "WORK!"

    So I looked around. They are now rare and expensive. eBay has ONE at a wacky price. Meaning very high. mint...

    I wonder if we could make a knockoff? It must be out of patent by now...

  8. #8
    Corran's Avatar
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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    I've completely abandoned the "formulas" these days, because they are unnecessary. Bring along a little tape measure, smallest you can get because you won't need more than a couple feet (your 300mm at 1:1 would be ~24" of extension, if you even have that amount of bellows).

    Measure the total extension from the film plane to the center of the lens. That's your new "focal length." Decide what f/stop you'll be using. Divide the lens' nominal focal length by that aperture to get the size of the aperture in millimeters (e.g. your 150mm at f/22 = a 6.8mm aperture). Divide the total extension you measured earlier by that number and you have your new, corrected f/stop. So if your 150mm was focused out to 220mm, 220/6.8 = f/32, or a one stop correction. The extension measurement doesn't have to be exceedingly exact.

    This is way easier IMO. Others may disagree. Unless you need a specific magnification for scientific/measurement purposes, why bother calculating it?
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  9. #9
    Tin Can's Avatar
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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    I use it for magnification goals. It's mindlessly simple.

    Can you do that simple math in your head?

    I can, but don't want to. It's a distraction from my real goal.

  10. #10
    Corran's Avatar
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    Re: Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?

    Personally I don't even bring the little tape measure. I can eyeball it pretty well and yes do some quick maths and come up with a corrected f/stop that works, as far as my negatives are concerned (I am more likely to mess up my metering / zone placement than miscalculate bellows compensation).
    Bryan | Blog | YouTube | Instagram | Portfolio
    All comments and thoughtful critique welcome

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