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View Full Version : Bellows extension cheatsheet for SA 90 XL, SS 150 XL, 300M?



pchaplo
16-Feb-2018, 13:02
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

Bob Salomon
16-Feb-2018, 13:55
Why? It is pretty easy to just look at the gg. And what image ratios would you want it for?

Dan Fromm
16-Feb-2018, 14:03
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.

Drew Wiley
16-Feb-2018, 17:08
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.

Michael E
16-Feb-2018, 17:21
(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.

MikeMGB
16-Feb-2018, 17:28
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.

Tin Can
16-Feb-2018, 18:05
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 (https://en.wikipedia.org/wiki/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...

Corran
16-Feb-2018, 18:34
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?

Tin Can
16-Feb-2018, 18:42
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.

Corran
16-Feb-2018, 18:45
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).

pchaplo
16-Feb-2018, 19:13
Thanks Dan,

Good point. I will start with my 150mm.


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.

pchaplo
16-Feb-2018, 21:15
For just one lense, this would handy, and I found it here, contributed by “Richard” on QL’s Bellows Factor page
http://www.largeformatphotography.info/bellows-factor.html

I just need one for my 150mm Super Symmar XL.

174863

174864
Scale and pic by Richard

Anyone have one for 150mm that I could print?

biedron
16-Feb-2018, 22:14
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.

You can make your own using the download at http://www.salzgeber.at/disc/

Bob

Doremus Scudder
17-Feb-2018, 03:33
I don't want to do any calculating in the field. The exposure disc is a good tool, but having to place it in the scene is a disadvantage, especially in the field for found and delicate foliage shots, etc. I prefer just to consult a chart.

I've got my exposure record book with me in the field and that has charts for bellows extensions for all the lenses I commonly carry (plus reciprocity adjustments, filter factors etc., etc.) I only have to measure and look up my factor. I'm attaching the charts here for those that may find them helpful.

There's one chart in mm and one in inches so you can measure how you like. Feel free to copy, modify, whatever to suit your needs.

Best,

Doremus

Tin Can
17-Feb-2018, 04:56
Very nice Doremus and I mean that 2 ways.

Beautiful chart well sized to be usable on a phone or printed. Nicely done!

A wonderful gift and accommodation for metric or imperial practitioners. Nice!

Thank you!

pchaplo
17-Feb-2018, 10:58
Thanks Doremus for sharing the chart that you developed. I appreciate your kind generosity, and this tool will help many others for a long time!

Bill Poole
17-Feb-2018, 15:20
Another cheer for Doremus' chart, which is now where my phone can always find it. Many thanks.