Hi Rob, Thanks for your input: I guess the main object of the test is its infrared chracteristics, ie how well it will record the infrared spectrum (the film is said to be senstised upto 820 nm). So sharpnes isn't the main issue yet. I'll be shooting mainly landscape with some houses. Tonight I'll check if sliding a piece of normal sheet film underneath the thin film is a solution (i.e. if the film will be lying flat than, theoretically the sandwich is too thick, but I assume for the landcape stuff I indend to shoot at f16-f32 that should not matter). On the antihalation layer: at one time MACo markerted AURA film, which was basically a MACO 820c film (aka EFKE PL100 plus IR senstive dyes) without an anti halo layer. I was asked to test it out, but no matter how hard I tried I could never obtain the halo effects chracteristic of Kodak HIE, there was a very small difference between the AURA and the IR 820c film. Best, Cor > -----Original Message----- > From: pure-silver-bounce@xxxxxxxxxxxxx [mailto:pure-silver- > bounce@xxxxxxxxxxxxx] On Behalf Of Rob C > Sent: woensdag 4 april 2007 13:28 > To: pure-silver@xxxxxxxxxxxxx > Subject: [pure-silver] Re: (sligthly OT) Film flatness in a 4*5 holder > > I don't think anyone could answer your question with 100% certainty for > several reasons. > > For starters, if the film is loose in the holder, then it may be tilted > one way or another and also the center may or may not be in the correct > plane. > And it depends on what you have focussed on in the subject. i.e. was the > focus point in the center of the frame. > Also, some IR films have no antihalation layer and different IR films will > react to halation in different amounts. This may cause some films to > appear less sharp than others. > And was your subject planar and fill the frame completely so that you > would expect the same sharpness from edge to edge. > And was your lense at optimum aperture to obtain sharpness edge to edge. > > Depth of focus increases the closer your subject is to the camera so if > you want to remove depth of focus as a significant factor from your > testing, do some macro shots. But of course you then have to worry about > depth of field which is much reduced. But then if your subject is planar > then depth of field won't be an issue either. > > So your test results would depend on many factors and I guess it also > depends on what you are supposed to be testing. i.e. subjective or > objective tests. > > Rob C > > ======================================================================== == > =================================== > To unsubscribe from this list, go to www.freelists.org and logon to your > account (the same e-mail address and password you set-up when you > subscribed,) and unsubscribe from there. ============================================================================================================To unsubscribe from this list, go to www.freelists.org and logon to your account (the same e-mail address and password you set-up when you subscribed,) and unsubscribe from there.