Exposure compensation with bellows question.

[Bob Kerner]

+1 for Mark's method.

Or skip to 4:40 to hear the math explained and reference to the disc


And there are several smart phone apps that will do this for you. Reciprocity Timer is one such app.

Or explained another way:
Convert the focal length of the lens you’re using to inches. For instance, a
210mm lens is 8”.
8” (210mm) lens, focused at infinity. Bellows extension 8”
· Think of inches in terms of f‑stops: f8.
· Measure the distance from the film plane to the lens board.
· Let’s say the distance is 11”. Think of f‑stops: f11.
Bellows extension 11”, measured from middle of shutter to ground glass.
· The difference between the focal length, 8”, and the focusing distance, 11”,
can be thought of as one stop difference. F8 to f11.

Excerpted from Finely Focused

[Daniel Unkefer]

TTL 4x5 5x7 8x10 Broncolor Strobe Meters Norma Sinarsix Cassettes by Nokton48, on Flickr

I use the Sinarsix for TTL spot metering at the film plane. I find this to be the most accurate and quick method for my uses. I find the Olde Norma Lunasix Meter Probe to be deadly accurate for available light spot metering. The FCM2 measures TTL strobe and ambient, and is new to me. Love it. I may just stop bracketing after I get more confident with it.

[Eric Woodbury]

My rule of thumb.

Example: If I'm using an 8 inch lens (210mm) and it is focused at 11 inches, then that is the equivalent of one stop addition (in this not-so-cleaver example, notice that 8 inches would be like f/8 and 11 inches would be like f/11) Therefore, I change in opposite direction to compensate the f/# by one stop (from f/11 to f/8 or f/22 to f/16). No ruler needed if you can guess kinda close. Or mark a ruler on your camera to calibrate your guesses. When in doubt, give a little extra.

75mm = 3 inches, 100 mm = 4 inches, 150 = 6 inches 210=8 inches, 300 mm = 12 inches, etc.

Metric folks could use centimeters and it would work fine without a too many zeros involved.

[cowanw]

The “H” is designed to be a hand-holdable architectural camera for travel. How close does it focus?

[Daniel Unkefer]

How about this? My exposures TTL generally run within 1/3 stop of indicated.

Sinar Norma Handy w TTL Sinarsix metering by Nokton48, on Flickr

[Doremus Scudder]

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...

Well, I've made the chart and have it with me, but it's just the exposure compensation. That said, all I have to do is measure and apply the appropriate compensation; zero calculating anything. If I were doing lots of macro work (like you do), having a real, working f-stop value would likely be valuable. Still, I get around the whole depth-of-field calculation thing by using a focus-spread method of finding the optimum f-stop, which works regardless of bellows extension.

More than one way to peel the onion

Doremus

[Bernard_L]

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.

This can't be right. Assume you are taking a picture of an object "near infinity", i.e. far enough that one should not even worry about correction. Extension as you define it

Measure extension. This the distance the lens has been moved forward from the infinity position.

is close to zero; more precisely extension<<F.L.
Then the f-number following your recipe becomes "very small", like, e.g. f/8 becomes f/0.5, when it should remain f/8 or very close.
Your formula at step 3

Calculate effective f/number as f/number set * (extension / focal length)

should be:
Calculate effective f/number as f/number set * [(extension / focal length)+1]

Plus, there is an implicit assumption about the location of the exit pupil, but let's keep it simple.

[Dan Fromm]

This can't be right. Assume you are taking a picture of an object "near infinity", i.e. far enough that one should not even worry about correction. Extension as you define it

is close to zero; more precisely extension<<F.L.

Huh? When the lens is focused at infinity the distance from the lens' rear node to the film plane is the focal length. Exactly. Where the standard then sits is the infinity position. It depends on the lens' design type -- broadly, retrofocus, telephoto, neither -- and mechanical design and need not be 1 f from the film plane.

I did make a mistake, effective f/# is f/# set * 1 + (extension/focal length)

[Bernard_L]

Huh? When the lens is focused at infinity the distance from the lens' rear node to the film plane is the focal length. Exactly. Where the standard then sits is the infinity position.

Yes. and

Step 2. Measure extension. This the distance the lens has been moved forward from the infinity position.

the extension as you defined it is zero when focused at infinity. And the standard, rear flange, etc sit where they need sit.

[jmpgino]

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

Hello, sorry for the late reply had an accident that needed an emergency room visit and quite a few stitches in my hand.
The bellows are at the back of the camera. The lens fits onto the front of a body and the bellows if needed is attached on the back of the body. It has a ground glass that a focusing prism can be attached, once focused the prism is removed and the film back is then attached. Just got a Schneider 100mm f5.6 Copal 0, lens cost $530, the Silvestri bayonet mount cost me $450 a crazy amount for what it is. Have not yet fully tested it but it gets close enough for me if doing table top or a flower. Beautifully made equipment from Florence Italy, but very expensive.