Bellows Extension Compensation

[Andrew O'Neill]

I don't do a lot of close up work, so when I do, I sometimes forget to compensate... Three ways to figure out the extension factor, that I know of, anyway...

 

[Sirius Glass]

Great video. What I did was to use the formulas in a spread sheet to print out a scale for my 1953 4"x5" Speed Graphic with f stops along the length. I glued the scale to the rail. That way the location of the lens is over the f stop compensation. using the reading off the rail requires not tape measures.

No rulers or tape measures were injured or killed in the posting of this post on this thread.

 

[MurrayMinchin]

I don't do a lot of close up work, so when I do, I sometimes forget to compensate... Three ways to figure out the extension factor, that I know of, anyway...

Another great, informative video

Waaaaaay back in time (1980 or so) I spent a tedious afternoon with a calculator and figured out the BEF's for my two 4x5 field camera lenses. Once I had those figured out, I transcribed them onto a wooden ruler.

In the field I never had to devote brain power to BEF's again...I just pulled the ruler out of my camera bag, held one end of the ruler at the film plane, and noted what factor needed to be applied by where the lens board fell along the rulers length.

Never measured inside the camera with the lens off...just eyeballed it while keeping the lens on.

 

[cowanw]

As I was watching, I wondered if your reciprocity app was a weakness in your testing; was it the same exposure effect for 8 and 20 sec.? Seemingly it was.

I noticed the difference in density was not the same at Zone lll as zone X. Does this mean that the 2.5 X extra exposure is expressed at one particular zone or am I forgetting something (like logs)?

 

[Andrew O'Neill]

As I was watching, I wondered if your reciprocity app was a weakness in your testing; was it the same exposure effect for 8 and 20 sec.? Seemingly it was.

I noticed the difference in density was not the same at Zone lll as zone X. Does this mean that the 2.5 X extra exposure is expressed at one particular zone or am I forgetting something (like logs)?

It's not a reciprocity app. It's actual data that I generated years ago, by contact step wedges, and exposing them at 1 sec, 10sec, and 100sec (with the aid of ND filters for consistency). Curves were drawn, etc etc. It's been tested and used in the field for many situations and is quite sound. I keep that data, along with data for other films that I use, on my phone.
With increase in exposure times, comes a bit of contrast increase with this film, which can be compensated for by reducing development. I prefer not to do this, as most of the time I'm developing for Alt processes like Carbon Transfer, which benefits from this.

 

[grahamp]

I usually carry a flexible tape measure, but I have been known to forget it or leave it in another bag. Fortunately my hand span is exactly 9 inches, which is better than a pure guesstimate.

I keep meaning to put a scale on one edge of my dark cloths.

 

[Sharktooth]

I keep meaning to put a scale on one edge of my dark cloths.

That's what I do. I sew one of those sewist tape measures to the bottom edge of my dark cloth. I also sew a little pouch on my dark cloth to hold a paper printout of extension factors for various distances for each of my lenses. No calculations to make, and it's always there and ready when needed. If you forget your dark cloth you've got far bigger problems to worry about.

 

[Alan Edward Klein]

I tried this is a dry test and seems to work pretty nice. YOu place the disk and check where the aperture should be set. Then remove the disk and click.

QuickDisc Home Page

The Quick Disc is a simple but effective tool to determine the exposure compensation when photographing small objects with large format cameras.

www.salzgeber.at

 

[Pioneer]

I don't do a lot of close up work, so when I do, I sometimes forget to compensate... Three ways to figure out the extension factor, that I know of, anyway...

I ALWAYS forget to compensate...until I get home!

Nice video, thanks for posting.

 

[cowanw]

Thanks

 

[Chuck_P]

Nice video........thank you. I'm catching up on some threads as I've been away for a while.....and thanks for the Quick Disc info.

 

[btaylor]

I tried this is a dry test and seems to work pretty nice. YOu place the disk and check where the aperture should be set. Then remove the disk and click.

QuickDisc Home Page

The Quick Disc is a simple but effective tool to determine the exposure compensation when photographing small objects with large format cameras.

www.salzgeber.at

Thank you for this, Alan. I had seen this or something like it years ago and I forgot about it. I have now printed it out, I like simple and I don’t think it gets easier than this!

 

[Andrew O'Neill]

I show the QuickDisc towards the end of the video. The link to the QuickDisc is in the video, as well as in the description. It's a neat gadget, but please remember to remove the disc when you go to take the picture!

 

[btaylor]

I show the QuickDisc towards the end of the video. The link to the QuickDisc is in the video, as well as in the description. It's a neat gadget, but please remember to remove the disc when you go to take the picture!

Sorry, Andrew. I have to admit I have not yet watched your video and just went to Alan’s link. Thanks for all of your contributions and clarifying the attribution.

 

[RalphLambrecht]

Here is a variation of the same idea: flip through the pages to find some useful helpers