I have a question that I hope to explain clearly so please bear with me.
IF I were to shoot at an evenly lit target at less than the focal length of my lens what would happen on the film ? Would I get an uneven exposure ?
OK so picture this. I shoot at my lightbox with my lens set at infinity (large format) and the subject distance of say 100mm from the 180mm lens.
OK so take it to the real world. Can I shoot through something like an Expodisk which is attached to my LF lens to get an even exposure across the film ? Why ? Pre-exposure film flashing.
I think I am seeing a variation in exposure doing this.
I've a feeling that if I want to get an evenly exposed sheet of film I should shoot an evenly lit target and maybe be only slightly out of focus to try and blur any inconsistencies in the target ? Obviously I can't focus on an Expodisk that is attached to the lens ... so if I focus on a lightbox at a couple of feet ?
The question comes down to the behaviour of the lens due to its design I think. I don't know enough about lens design to answer my own question.
The issue doesn't arise of course for those SLR digital types who may only be using the information the Expodisk conveys at the very centre of their viewfinder on spot metering I guess. Can one use an Expodisk to evenly expose a sensor for dead-pixel testing or something ? I don't have a digital SLR ...
Does the same thing apply for those white lens caps ?