Record Sheet from a class long ago.

[bobwysiwyg]

I was hoping someone here might be able to explain some of the content on this record sheet. I, and other class members, were given it many years ago in a local photo class, aimed primarily at printing. At the time I was entirely into 35mm so much of the sheet content seemed not to be relevant. With my efforts to learn my 4x5, perhaps it now has some meaning and usefulness.

The upper part seems related to the zone system. It is the middle part that I'm having trouble deciphering, where there are listed focal lengths and extensions. I'm assuming this is related to additional exposure times for the extensions??

Anyway, any input would be appreciated.

 

[Ian Grant]

You're assuming right but in over 40+ years of photography I've never found a need for something so complicated.

Ian

 

[bobwysiwyg]

I can appreciate the observation about it being complicated, but since it was devised by someone with far more experience than I have, I thought it might be of some value.

 

[Ian Grant]

Now come on scratch your head and remember what you were taught

It's a record sheet for shooting (& then printing), the bellows extensions are the exposure factors factors for shooting LF with different lenses. I simplified this by marking my Wista trackbed with an indelible black marker for my 90mm & 150mm lenses, indicating the extar exposure needed in half stop marks.

Ian

 

[bobwysiwyg]

One thing I do remember is that I was never very good at discerning 1/2 stop differences.

 

[David A. Goldfarb]

From the filename I gather that's Howard Bond's exposure sheet? Interesting.

The middle section gives you exposure factor based on bellows extension past the infinity position. So if you have a 150mm lens and you need to focus 2.5 inches past the infinity position, you need to add one stop additional exposure. The focal length range in the chart seems designed mainly for shooting 8x10".

Then there's a table that's lined up with the bellows factor chart of standardized exposure times that says if the exposure on your meter says 2 sec at whatever aperture you're using, give 4 sec. (and don't forget about reciprocity on top of that). I don't think this table is so useful, because it suggests that you would adjust your aperture to use the "indicated" times in the table, rather than selecting the aperture for what it does to the image (i.e., DOF and diffraction).

Personally, I figure bellows exposure factor by estimating or measuring the magnification of the subject compared to the dimensions of the format, and then I have a table taped to the back of the camera to convert magnification factor to exposure factor. I like this method, because it works the same way with any lens, any format, and you don't need to measure anything on the camera.

 

[bobwysiwyg]

David,

Thanks for taking the time for the detailed explanation. Yes, it was a Howard Bond class.

 

[wclavey]

Just getting back to reading after severals days of inactivity because of the hurricane here in Houston...

This is an interesting record sheet. I developed one of my own for LF and continue to modify it over time and it looks surprisingly like this sheet... I guess there is only so much information worth collecting.

I had this one made into a rubber stamp, 2x3" and I stamp it on the top of a journal page and then take other notes below it when I shoot LF.

 

[Anupam Basu]

I never can understand why one needs to get into such a twist over extension factors. If you need to calculate the factor, get out your cell phone and use the calculator function. (Extension/focal length)^2 You can read the extension off the bed of most cameras. Divide it by focal length (i.e. extension at infinity) and square it. Probably much quicker than poring over a chart.

-A