Super friggin cool bellows factor compensator thingie.

[JBrunner]

There's a few of these around. Most are better than mine, but mine is distinctly super friggin cool. I stuck the link in my signature. Enjoy.

[richard ide]

Thanks Jason. Will be put to use tomorrow.

[Steve Sherman]

You want to know how many stops to adjust for bellows factor?

Try this really super trick idea.

Take the lens you are using and convert it to inches, a 210mm lens is 8 1/4" if your bellows is racked out to 11 inches, you are basically at a one f-stop increase, ( convert the inches to f-stop numbers) f 8 to f 11 is one stop. Rack out to 16 in. and you are twice as long as lens, so you would be at 2 full f-stops. This would also be life size and I can't imagine having much need for any further magnification. It's all proportional, go down to a 6" lens racked out to about 8" and you would again have about a 1 f-stop increase in exposure. It is easy to calculate fractions of inches using 1/3's of f-stops.

For those who question if this method is precise enough, I used this method for years in table top photography using chrome film which demands much greater accuracy than does panchromatic films.


Cheers baby!

[Jim Noel]

I'm gvlad you think so much of the BF calculator. It is nothing new. I made one like it in the 1940's after reading an article in one of the mags of the time. Calumet sold one for many years, and may still do so.

Isn't it odd how old ideas come around and are "rediscovered" by a new worker.

[JBrunner]

I'm gvlad you think so much of the BF calculator. It is nothing new. I made one like it in the 1940's after reading an article in one of the mags of the time. Calumet sold one for many years, and may still do so.

Isn't it odd how old ideas come around and are "rediscovered" by a new worker.

Like I said, there's a few of these around. I've been using the Calumet version for years. It finally ratted up so bad I couldn't read it, so even calling it "rediscovered" would be a stretch, because I never lost it, but there are probably a quite few people new to LF that haven't seen one. I just made a super friggin cool new one.

[jnanian]

jason

the focus image is the bomb. <g>
thanks for the coolstuff!

john

[rwyoung]

I just keep a tape measure and a cheap calculator in my bag. The tape measure has both inches and metric scales. Measure from apeture to film plane (D). Then compute D / focal lenght of lens and square it. That is your compensation factor. Relatively easy to convert from that to stops or adjust exposure time. Most of the time I don't even bother with the calculator, you can get this pretty close in your head after a few times.

Just remember to measure from the apeture, which is not necessarily the lensboard.

But you know what would be fun, offer the same thing without your fabulous mug, as a TIF or similar so that people can insert their own super friggin' cool image. Of course you should do a little branding so that with your fabulous mug it is the "deluxe" model...

[JBrunner]

I just keep a tape measure and a cheap calculator in my bag. The tape measure has both inches and metric scales. Measure from apeture to film plane (D). Then compute D / focal lenght of lens and square it. That is your compensation factor. Relatively easy to convert from that to stops or adjust exposure time. Most of the time I don't even bother with the calculator, you can get this pretty close in your head after a few times.

Just remember to measure from the apeture, which is not necessarily the lensboard.

Math make brain hurt. Solution: Keep brain wet.

Seriously, there are about 7 ways to do this. All I know is I never screw up with the BF calculator. However, whatever floats your boat. We all tend to work with what we are comfortable with, and for some reason it is usually the first way we learned how to do something. Steve's and your method was the second way I learned. I've never been much of a slide rule type of photographer. I try to keep that side of my brain as un-engaged as possible during photography.

[David A. Goldfarb]

I use a similar method, but without a target, so it works for small formats too. I just have a table with magnification factor and bellows factor taped to my meter and all my camera backs. I compare the width of the scene at the subject distance to the width of the format to determine the magnification factor, usually estimating, but if I'm unsure or if it's a still life, I might actually put a tape measure in the scene, like the target in Jason's thingie or the Calumet thingie or the thingie linked to the lfinfo.com page, and then I look up the magnification on the table to get the bellows factor.

[CPorter]

I tried to open the link on your site Jason but when I do it locks my computer up, oh well.

This is not to tell you how to do it, but for LF beginners with rails like myself that may want to use this method: I just use the millimeter scale on my rail. When the inside to inside measurements of both standards are at 126mm apart, I know that my 210mm lens is at infinity. I simply made up a small chart with the extension factors at 1/2 inch increments forward of inifinity to about 5 inches. Did the math one time for the chart (just a few minutes). So, when the inside distance of the standards are, say,at 178mm, that's 2 inches forward of infinity, and my chart says 1.5x.