Quote Originally Posted by Guillaume Zuili View Post
I did a 16x20 test today. Very weird day with the sun diffused by a lot of smog. Amazing how fast the exposure was. 5 minutes top and for sure it was over exposed.
Was it because of this huge diffused light ?
YES

the use of a difusing material in many different ways in contact printing may be found in literature from 1800's to present day

when u have a large difuse light source,, the time factor comes in to play

the longer the exposure the more the difusion of the light inside the layers of materials in the frame-this can goto positive feed back --the opposite of self masking

also: the contrast of the finished print was controled back in the day by using direct sun or open shade(large difuse light source)-

the speed of the materials was different under direct sun from skylight which was usualy faster-depends on the process

you have discovered for yourself a most important technique in contact printing- -if you take detailed notes every time you make a print you will have a journal that will be your own cookbook with recipes for success-

vaya con dios