Scope Diagram

  Provia 400X vs. E200(+3)



More Notes


On this evening (9/15/2007), my intention was to shoot some long exposures on deep sky objects and at the same time try outa roll of Fuji 400X medium format (120) slide film given to me as a sample. My primary scope was to be the f/7 AP155EDF,so I elected to shoot Kodak E200 and apply a +3 push processing (ISO 800 according to Kodak) in order to keep theexposures down to a reasonable time (1 hr). Processed versions of the E200 photos can be seen on a separate page.

My test scope in parallel shooting the 400X film was a Borg 100ED operating at f/6.4. I elected not to push process the 400Xin order to get a feel for its behavior with normal processing. Although comparison with the E200 is not one-to-one,it is close enough to draw some conclusions. In particular I was looking to see if the sky background on 400X stayed relatively neutral, and how sensitive it is to H-alpha light.

The comparison photo (click on the thumbnail at left) was snapped with a digital camera (Nikon D70s). Provia 400X ison the left, while E200 is on the right. Each frame on the left has the same target as the frame on the right in the same orientation, although at different focal length. In the center, some daylight slides are shown for color reference. Everything was laid out on a slide viewing box and, with room lights off, photographed at one time. I've slightly adjusted the color balance so that the image matches what I could see visually.

Conclusion: As can be seen in the comparison photo, while the sky background is slightly green, it is correctable in post-processing. Note that under skies with less light pollution, the green cast may be negligible. However, H-alpha response is weak, as is typical these days for most "normal" films. I may try another roll in the future to see how it responds to push processing, but Kodak E200 will remain my film of choice.