minus filter and belows factor

im guessing that the bellows extension using the minus 4 filter

will need to be factored in as my shutter is calibrated for 135mm?..

it looks like the minus 4 is about 2 times as long by the almost

double size of the christmas tree in the ground glass when focused at

the same distance.. .. if that is the case would i open one stop? i

can measure mm distnace to glass to get correct exposure

difference?? someone said to put the minus toward the film.. their

is a minus but its not on one side or the other its on the edge..??

any help appreciated..dave..

You seem to have the idea, Dave. You do have to apply the appropriate bellows factor to your exposure when using minus lenses; I always measure the actual extention before shooting and have made a little cheat-sheet for each lens that I use the minus lens with so that I don't have to do many calculations in the field. The minus lens requires no adjustment for density.

Many minus lenses come with a little arrow that points toward the subject when the lens is used on the front of your taking lens(as I usually use it); if I remember correctly, someone mentioned that it should point toward the film if you are using the minus lens on the rear of your taking lens. I have never used it this way, so if I have it wrong, someone will correct me, but I think you'll know if you have it right just by looking at the ground glass.

Vick's right on! I use my minus(-)lens on the rear element when its diameter is too small for my front element. Alfred Blaker's book "Field Photography" Table, on page 366, calls for a +2 stop correction when using a 135mm prime lens and a -4 diopter lens.

Harry

There is a good article on this very subject in the magazine "View Camera" November/December 2003 issue. The Method of

Varying the Focal Length of Large Format Camera Lenses by Robert Havira. He covers the use of minus lenses on the prime lens rear element on page 43.

Harry