light meters

[absolom]

Are there any light meters that take into account bellows extension?

[Jay DeFehr]

Sort of. The Sinar metering backs meter at the film plane, with appropriate accessories, so that takes everything into account, including bellows, filters, etc. Lacking that, if you calculate the bellows factor, you can enter the compensation factor into your meter (some meters) and read the meter directly. Is this what you have in mind?

[vinny]

after doing closeup work for a while with a particular lens, you'll know how much to adjust for via the ISO dial, w/o measuring the bellows etc.

[Shen45]

Not to my knowledge but the Expodev application for BTZS as used on the Palm or now on the iPhone accounts for Bellows filters and reciprocity. It only workes though with data test files for the BTZS [system].

Many experienced workers use a simple method of 25% bellows extension = 1/2 stop exposure increase. Eg a 12" lens at 15" add 1/2 stop of exposure.

[Leigh]

Many experienced workers use a simple method of 25% bellows extension = 1/2 stop exposure increase. Eg a 12" lens at 15" add 1/2 stop of exposure.
That's mathematically correct and accurate.

Mark the position of the front standard when the camera is focused at infinity,
then measure its position when focused on the subject as desired.

The difference between these two values equals the bellows extension.
For a life-size image (1:1 ratio) the extension should equal the lens focal length.

The extension divided by the lens focal length is the extension factor.

The method given is accurate for any lens.
Making a single measurement in the close-focus position and assuming the lens focal length
as a starting point can introduce a significant error with some lenses.

To answer the OP's original question...
Any throught-the-lens (TTL) metering system will automatically compensate for bellows
and for any lens attachments or modifiers.

- Leigh

[Two23]

Get a Quick Disc and you can use any meter.


Kent in SD

[absolom]

Jay,

Yeah, entering the compensation factor into the meter is what I had in mind. I can of course just do the math myself but I'm considering buying a new light meter and was wondering if there were any that had this feature. Any specific recommendations?

[Drew Bedo]

Nothing beats informed experience and a few bad negatives. Do the math for a while—eventually you'll be able to make the correction without thinking much.

Seriously: Pre-figure the correction for your favorite lens(es). For a 150mm lens, each inch of extension beyond six inches requires 1/3 stop additional exposure. For a 210mm lens the correction for each inch of extension beyond 8 inches is 1/4 stop additional exposure.

Figure it out once and write it down. Use a short piece of cloth measuring tape to check the distance from GG to the lens board (OK the primary node) and check your pre-figured table. After a while this will become part of your process.

[BetterSense]

1:1 is 2 stops.

It's easy to remember, and you can interpolate tolerably well for less/more magnification.

[Jay DeFehr]

Jay,

Yeah, entering the compensation factor into the meter is what I had in mind. I can of course just do the math myself but I'm considering buying a new light meter and was wondering if there were any that had this feature. Any specific recommendations?

I think most meters can be made to function this way, by one method or another. Altering the ISO setting might be the most universally available method. For instance, if your bellows extension is 50%, and you're using ISO 400 film (and rate that film at EI400), you can simply set your meter to ISO 200 and read it directly. Different meters have different kinds of exposure compensation mechanisms, but they all accomplish the same thing as adjusting the ISO on the meter. I hope this helps.

[Clive Gray]

You can also use the film plane metering probes from the Sinar system with non metering backs or other makes of camera if you have the metering cassettes it is less ideal but perfectly useable.

[Ivan J. Eberle]

Learning how to program a meter or compensate it is probably about as difficult as doing the maths in your head. The benefit of not offsetting the meter is the next reading will not be skewed if you forget to zero out the meter.
If shooting modern neg films, it's all pretty easy. If transparency, it's more critical.

[Doremus Scudder]

I think many make the issue of compensating for bellows draw much too complicated.

My solution: A table with bellows compensations for all my lenses and a small tape measure.

By the time you've put your disc in the scene and taken it out again (and then measured it on the ground glass and consulted a table...), or fiddled with your iPhone or hand-held computer, or twisted the ISO dial on your meter (which you may forget to reset...), or done the mental gymnastics to come up with a rough estimate (and maybe not got it right... do it again to check...), I've measured my bellows draw and looked up the exact compensation in either shutter speed or aperture change on my little table.

If you're dealing with close-up work, the time it takes to measure bellows draw and consult a table is a miniscule fraction of the time it takes set up the shot and is often fewer steps than other methods of finding the bellows compensation. Plus, it is accurate and you don't have to do calculations when you should be concentrating on composition and getting the shot right.

Best,

Doremus

[Henry Larson]

Are there any light meters that take into account bellows extension?

My LunaPRO sbc has a bellows extension function.
It is described in detail in the Lunapro sbc instruction manual

[Jim Jones]

Some small format macro accessories such as bellows and extension tubes came with a scale to be placed in the plane of focus which would directly read information such as magnifiation and exposure factor. This one came with Spiratone extension tubes. The inch and metric scale is not part of the macro scale, but added for reference. A similar aide for any large format could easily be calculated by anyone proficient with modern calculators. I'm too rusty with a slide rule to volunteer.

74155

[Leigh]

A similar aide for any large format could easily be calculated by anyone proficient with modern calculators.
Calumet sells such a set for $10.95 IIRC. I bought a couple of them last year.

It consists of two pieces:
1) a high-contrast square target that's placed in the scene at the desired plane of focus; and
2) a little scale to read the bellows factor directly from the image of the target on the ground glass.

Very nice item.

- Leigh