I have heard that when using large coverage lenses, such as 400mm on a samller f ormats, say 4x5 or even 6x9, that a lens hood or compendium shade is necessary t o reduce the amount of light that is entering the camera, so that it is limited to an image circle slightly larger than the film being used. Supposedly all th is extra light that bounces around indside the camera causes loss of contrast an d sometimes creates some strange flare. The theory is, the inside of a bellows, does not absorb 100% of the extra light, so therefore the non absorbed rays bou nc around, allowing some to get on the film or interfere with the light rays bei ng absorbed by the film.
Before I try to run some test shots of this, I was wondering if anyone has any experience with this. Of course if you are using lenses that are suited fo r a given format, than I guess this is not a problem. However, all my lenses wi ll cover 8x10 with plenty of movements, but I shoot mostly 4x5 and 6x9. Any inp ut would be appreciated.