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Photography and Photoshop Tutorials
Bellows Extension Calculator
Online bellows extension factor and exposure compensation calculator and printable exposure compensation scale

Here is a quick way to calculate the bellows extension factor and exposure compensation amounts for large format view camera users in the studio.

To use the calculator follow this link.

Online bellows extension factor and exposure compensation calculator...

However when you are working in the big room there is no computer or webbernet so the online calculator is not an option...

For years I have calculated my bellows comp in my head for large format. I always enjoyed using my RB-67 partially because of the bully bellows comp scale which made the bellows factor calculation into a non-issue.

I wanted to improve my large format production rate as it is a notoriously slow process. This was one of the points where I saw that it could be better, not that it took me that long to figure out the factor but just having to go into math mode detracted from the experience of vision and visualization.


I have carried a legal size xerox of a ruler which I coated with packing tape on two sides for years. When backpacking a 4x5 I try to keep the kit light.

I decided to make a scale that was like the RB-67 scale which covered the lenses in my kit while giving me an inch ruler as well.

I immediately noticed that there were not many simple calculators for bellows extension on line so I fixed that...

While I can't use the online version in the field it will certainly did enable me to make an excellent paper ruler.

I first made a 2 inch tall version and hindsight being 20:20 I decided I wanted it even smaller so I transformed it to make a 1 inch version. My Zone VI field camera has a 300 mm maximum bellows draw so my ruler ends in that range. The ruler is around 14 inches long.

Here are links to the two rulers, the 2 inch and the slightly more compressed 1 inch version.

Large Bellows Extension and Exposure Compensation Ruler

Small Bellows Extension and Exposure Compensation Ruler

For the mathematically minded out there (not me) here is the formula that I used for the online calculator:

  • extension is bellows extension in mm
  • focalLength is focal length in mm
  • factor = (extension * extension)/(focalLength * focalLength)
  • stopsCompensation = log(factor)/log(2)


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Web Site by Cooksey-Talbott Studio

Fine art photography of California by master nature photographer Cooksey-Talbott. Hundreds of beautiful photographs are displayed for sale online as raw or ready to hang images.

Cooksey-Talbott Gallery is an online gallery of nature photographs. The collection includes pictures of the High Sierra, Ansel Adams Wilderness, Yosemite, Trinity Alps, Sonora Pass, Santa Barbara Hills, East Bay Hills and Garin Park as well as hundreds of different waterfalls. Legacy images are from medium and large format film taken with the Mamiya RB-67 and a variety of 4x5 view cameras. Some of the more recent work is shot with a Nikon D200, Canon 5D Mark II and the Sony A7r.

We offer archival quality prints in a wide range of sizes and media. We print on a heavy art papers and canvas using a Canon iPF8300 44 inch 12 color printer with pigmented inks. Our images are first party prints made directly by the artist. Prints are signed and numbered and include a Certificate of Authenticity.

Ralph Cooksey-Talbott Thomas has been working as a photographer since 1972 when he moved to California from Michigan. During the 1970’s he studied under Ansel Adams in Yosemite. Ansel published one of his photographs in the portfolio section of his book "Polaroid Land Photography" Ansel and Orah Moore, another of Ansel’s students, suggested that he shorten his name to Cooksey-Talbott, and that is the name he has worked under since. Cooksey also studied at the San Francisco Art Institute and the San Francisco Academy of Art. He has lectured in photography at the U.C. Berkeley Extension, Studio One in Oakland and Santa Barbara City College. Cooksey is currently working as a photographer and facilitating which is a monthly photo walk that meets up in Niles California.