Question about long exposures - bulb mode in DSLR's

episodic

I'm looking at an entry level dslr

I've narrowed it to two -

Either a pentax k110d or a nikon d40

Price is a major concern.

Second - will both of these do long exposures? I'm looking to do things like star trails and extended night shooting, etc.

Finally, which is apt to last longer and not break?

Also - will using the bulb mode alot (like for 30 minute exposures or longer) -wear the camera out faster?

TIA - I know I've asked alot.

ziggy53

How much research have you done to determine what it is that you need to make long exposures and star trails?

What will be your procedure for star trails, long exposure or multiple exposure?
What lens specifications have you chosen and why?
How important are batteries and power efficiency in your choice? (I know the answer, but I want you to research it somewhat.)
Have you investigated the light pollution in the site where you plan to shoot?
Which is typically better for these tasks, CCD or CMOS, and what do these two cameras use?

episodic

ziggy53 wrote:

How much research have you done to determine what it is that you need to make long exposures and star trails?

What will be your procedure for star trails, long exposure or multiple exposure?
What lens specifications have you chosen and why?
How important are batteries and power efficiency in your choice? (I know the answer, but I want you to research it somewhat.)
Have you investigated the light pollution in the site where you plan to shoot?
Which is typically better for these tasks, CCD or CMOS, and what do these two cameras use?

Both these cameras have pretty good power ratings with the Nikon being the clear winner.

At first, I'll have to shoot with the kit lens - that should not be problematic though. I have a good tripod already. I know about light pollution. Don't know the cmos vs. ccd question.


My main question is - Is using bulb mode 'hard' on the camera?

mr peas

"Which camera will last longer?" Thats really hard to tell. Theyre both entry level DSLRs, I'm sure they will last at least 25k-50k+ exposures, similar to the Canon Rebel XT.

"Will using the bulb mode alot (like for 30 minute exposures or longer) -wear the camera out faster?" It will use less shutter movement. For ex, 4 quick shots at 1/15th a second will trigger the shutter 4 times, versus a shutter held open for 60sec will only be triggered once. Therefore, bulb mode would probably have less wear on the camera.

But honestly this is something you need not worry about. Unless you plan to shoot over 300 shots a night, you wont be putting too many shots on the camera to begin worrying about it. I would be more worried about how long you will hold out until you find out that your entry level DSLR is less than satisfactory @ 6megapixels when you can easily go up to 8megapixels for the same price you are willing to pay.

Have you considered buying a used Rebel XT? or even a new one? @ Dell.com they are $500ish dollars new, probably save 50-100$ if you buy it used from the for sale forum here. Of course, it will also depend on what lenses you already own. If you have Nikon or Pentax bodies, then it would be wise to pick up the same brand DSLR. But if not, I (being a Canonite) would suggest you pick up a Canon Rebel XT from Dell.com for $500, ask around here for someone to sell you a 17-55mm kit lens for $50-$75, and buy a Canon 50mm 1.8 lens for $75 shipped from Amazon.com. That is, if you're not in a hurry.

I hope that helps.

ziggy53

episodic wrote:

Both these cameras have pretty good power ratings with the Nikon being the clear winner.

At first, I'll have to shoot with the kit lens - that should not be problematic though. I have a good tripod already. I know about light pollution. Don't know the cmos vs. ccd question.


My main question is - Is using bulb mode 'hard' on the camera?

Good answers! I'm glad to see you spending some time thinking about this.

The thing to remember with dSLRs is that in long exposures, they are always on. If you plan a 1/2 hour exposure, you also need to include 1/2 hour for the black frame. That's one full hour for a single exposure. It's pretty hard on batteries. I don't personally think that either camera mentioned is particularly appropriate for the task.

A better approach (IMHO) with this level of camera is multiple shorter exposures, stacked together.

Information available here:

http://www.astropix.com/HTML/I_ASTROP/TRIPOD/TRIPOD2.HTM

As far as damage to the camera due to long exposures, some have commented that the imager does heat up during long exposures. This can contribute to premature failure, usually limited to individual photo-sites (pixels). These pixels usually go "dead" and would need to be mapped out by some means. Other considerations are the exposure to the elements, which can lead to related problems.

You may (probably) have condensation problems with the lens. The best solution I have heard of is the use of disposable hand-warmers, attached to the lens to keep it slightly warmer than the ambient air temperature.

I couldn't find anyone online using either of these cameras for what you wish to do. Both are CCD imagers.

It is generally considered better to use CMOS imagers for long exposure photography (banding issues with CCD), but recent technological advancements have narrowed the differences considerably, and cooling technology can eliminate most of the problems altogether (which is why dedicated imagers used for astronomy often have cooling mechanisms attached to the imager itself.)

If you are determined to do a lot of long-exposure night photography, you might consider using an older film camera with a mechanical shutter.