No, I have little experience with long exposures. Just wanted to mention the reciprocity failure. What I discovered in my film days was that once I exposed long exposure time would increase even more due to Schwarzschild. I also have the impression that the lack of reciprocity failure on CCDs is one of the main reason astronomers went for CCDs quite early. I also got the impression that quantum efficiency is much better on sensors compared to film.
Now, if you have tested both you obviously know what works best for your application.
I'm very much aware of negative film handling the high end of the brightness scale differently from digital. I'm doing some testing on it right now. Interestingly I have seen widely varying figures. The film I'm testing is Ektar 100, and my initial measurement gave 12 stops, but those measurements may have some issues, so there will be a retest. Roger Clark reported 7 stops for Kodacolor Gold ( http://www.clarkvision.com/articles/film.vs.digital.summary1/index.html
) and Tim Parkin about 16 stops for Portra.
Going back to the original posting, Tim Parkin posted some very interesting points on the 8x10" vs IQ180 test: http://www.landscapegb.com/2011/10/the-perils-of-testing/
My own view?
- Well to me it seems that my Pentax 67 using Velvia is about on par with my 24.5 MP digital DSLR
- Ektar 100 scanned on my own CCD scanner (Minolta Dimage Scan Multi Pro) has somewhat less detail than the DSLR
- Colors are less consistent both on Velvia and Ektar
- Professional drum scanning gives better results than my own scanning
- Tonal separation on low contrast detail is weaker on Ektar than on my DSLR
- Extrapolating from this I would not expect a Phase One IQ180 to match a well executed 8x10" film image when properly scanned
- But, 8x10" is very demanding and a perfect exposure may be hard to achieve
On the other hand I find digital more practical, and I have not seen that much real benefit from my testing the 67 film based equipment.
I happen to use this exact Kodak data sheet for my long exposures (well, at least used to, now I just memorized it from using). It does require some tuning.
But I think you've missed my point. The first exposure I presented was around 20 minutes, the equivalent digital one (canon 5d mark II), considering the film reciprocity compensation was around 8 minutes (the correct exposure) and it had absolutely, completely, totally blown sky. No RAW processing could recover it.
I shoot a lot during these hours of the day and know for sure that it's not possible to accomplish a long exposure with my digital equipment without some very heavy filtration or tedious expo blending.
The same goes to the second long exposure and to the winter tree. In the winter tree scene, conserving the shadows in digital means blowing off the lights and the highlights or doing exposure blending. BW film just gets it from one click
I don't know what's your experience with long exposures is but digital or film, the scene reading are the same. For instance, during a starry night with no moon, I'd need more than just a few minutes of exposure with my digi, frequently half an hour or more, given the dark frame and cold weather I deplete a complete battery in just a few shots.