Originally posted by Garlic Capital Newby Hi, all. I finally got a chance to use my new K2000 yesterday, and in the process of exploring what it can do, I found the Bulb setting. Hallelujah! Remembering what fun I had using it on my K1000 and B&W film, I tried it a couple of times; no joy. Nothing but white on the LCD monitor. My question is this; seeing as how with color film you can experience that pesky reciprocity error if you have the shutter open too long,
I think it goes without saying but a digital imaging (in this case, CMOS chip) is not film and therefore, it does not suffer from reciprocity failure. As a side note, I had experimented with virtually eliminating reciprocity failure by way of gas hypering. It is oxygen molecules that actually help cause reciprocity failure. Between gas hypered film vs regular film, the differences were astounding!
Anyhow, with the CMOS imaging chip, you have something far more 'sinister' to deal with, that is, noise! The longer the exposure, the hotter the chip gets, and that introduces a lot of noise. Unfortunately, Pentax digital cameras are not as well suited for longer exposures as some other cameras. But pro (specially designed) cameras actually combat this heat by way of cooling systems. A properly cooled imager will keep collecting those meager photos happily for as long as they are turned on.
Originally posted by Garlic Capital Newby how long is long enough for the Bulb setting on a DSLR, and what is the optimal range for f-stops?
I'm not sure how to answer this question. Long enough? Depends really on what you are photographing. One of the ways to combat noise, is to keep your exposures short but take many pictures. In post processing, using a method called stacking, one can achieve the results of a longer exposure.
In regards to f-stops... next to wide open. Stopping down a bit will help eliminate any edge lens distortion on many lenses. Again, depends on the subject.