Exposure compensation with bellows question.

[jmpgino]

Hello, I am a little perplexed with this question. I have a rather extensive Hasselblad film camera system, the lens and bellows combination for close up imagery has an exposure increase indicator on the bellows.
Now i have a Silvestri H camera with bellows for two of my lenses. I am using the camera for 6x9. Now the bellows does not have any indicator for exposure, so my question is how do those of you doing close up work calculate exposure increases ??
I have only had the Silvestri for a short time and am still learning with it.
Thank your for any help in advance.
Cheers,
James.

[Vaughan]

https://www.salzgeber.at/disc/disc.pdf

[Kevin Crisp]

What he said, it works great.

[Dan Fromm]

Hmm. I use a slightly roundabout way to do it.

Step 1. Focus the lens at the desired magnification, i.e., set the shot up.

Step 2. Measure extension. This the distance the lens has been moved forward from the infinity position. I measure how far the front standard has moved cos the cameras I do this with have fixed rear standards.

Step 3. Calculate effective f/number as f/number set * (extension / focal length). When extension/focal length = 2 (image on sensitized surface the same size as the subject), f/8 set becomes f/16 effective. And so on.

I do this in the field, carry a small tape measure with me.

[Mark Sawyer]

Or...

You can measure the bellows extension and aperture and divide to find your actual f/stop.

It's in the name "f/stop".

"f" means "focal length"

"/" means "divided by", (or in fractions, "over").

"stop" means "the diameter of the aperture stopping the light".

It's not that hard, people...

[Doremus Scudder]

Or...

You can measure the bellows extension and aperture and divide to find your actual f/stop.

It's in the name "f/stop".

"f" means "focal length"

"/" means "divided by", (or in fractions, "over").

"stop" means "the diameter of the aperture stopping the light".

It's not that hard, people...

Well, getting situated in front of my camera lens to measure the apparent aperture usually is either impossible or puts me in mortal danger And, I have similar problems placing a target in the scene; either it won't stay put or the delicate subject may get damaged. So...

Using the method:

Ext² / Fl² = Exposure Factor
Where Ext = Bellows extension measured from film plane to lens nodal point (middle of the lens for most designs)
and Fl = The focal length of the lens.

I made a small chart for all the lenses I normally use (75mm 90mm 135mm 210mm 240mm 300mm) working backward from the exposure factor series; 1.5, 2, 3, 4, 5, 8, 12, 16, 20. (that's exposure changes in stops of 2/3, 1, 1 2/3, 2, 2 2/3, 3, 3 2/2, 4, and 4 2/3 respectively). I simply carry the chart with me in the field (in my exposure record notebook)along with a small tape measure. If I think I need to add exposure to compensate for bellows extension, I just measure film plane to lens board and look up the factor for the lens I'm using on the chart. That seems to work well for me in the field with my wooden folders.

If I were doing lots of studio work with a monorail camera, I might be sure I have a scale mounted on the camera rail to save a bit of time.

Here's my chart for your extending pleasure
BellowsExtension.pdf

Best,

Doremus

[Alan9940]

Doremus,

Your method of calculating bellows extension is exactly the way I've been doing it for years. But, thank you so much for posting this PDF as I've always been too lazy to create one for myself.

[ic-racer]

The only measurement I usually do is on the ground glass. Like in post #2. Stops of exposure error are 2x the magnification of the image.
Another nice thing about the pritout in post #2 is that it can be printed any size, as long as the disk and measuring scale are printed on the same sheet. You can even make a mini version to use on the GG of a medium format camera.

[cowanw]

Is the bellows on the front or the back of the Silvestri H camera. How close can you focus?

[Mark Sawyer]

Well, getting situated in front of my camera lens to measure the apparent aperture usually is either impossible or puts me in mortal danger ...

I made a small chart for all the lenses I normally use...

If measuring the aperture is difficult in your usual situation, just make a chart of the aperture sizes at the standard f/stops. Say you have a 210mm lens; at f/5.6, divide 210mm by 5.6, your actual aperture size is 37.5mm. At f/8, 210mm divided by 8 is 26.25mm, etc. Now just measure your bellows extension and divide by your aperture size and you'll have your actual, real, working f/stop value.

Or you can divide the square of this by the square of that and get another number to multiply your exposure by...