5D long exposure battery life

[david_e._starr1]

So, I plan to be taking some very long exposures once I get my 5D. Some pitch black nature long exposures, ISO

50, maybe even an ND filter. So I'm thinking my exposure times might be upwards of even 45 minutes to an hour, for

some phenominal star trails.

 

Now, my question is regarding the battery life doing such a thing. Would the single battery have enough juice to keep

the camera on that long? Or would I need the battery grip (which I'm getting regardless), and would that even keep

the camera on long enough?

 

Also, the lens I'd use would not be stabilized.

[g dan mitchell]

You would certainly not use an IS lens (at least not with IS turned on) for such shots.

 

45 minutes and up would be quite long exposures. I doubt if you could take more than two of these, if that. In addition, you

would want to use the long exposure noise reduction setting for such long exposures... and for that you'll wait 45 minutes

after the shot for the black frame to be exposed.

 

Dan

[mark u]

You may want to think about your strategy for capturing these shots:

 

http://www.clarkvision.com/astro/canon-10d-signal-to-noise/

 

Similar considerations will apply with the 5D although the details will be different. Image stacker software and an intervalometer may be helpful. You can capture your own dark frames (I'd suggest one before a sequence and one after).

[david_e._starr1]

@G Dan Mitchell:

 

Is that with out without the battery grip?

 

And if I shot RAW and left the NR up to my computer, that would remove the 45-minute wait after the shot, right?

[mark u]

http://luminous-landscape.com/forum/index.php?showtopic=9736

 

Don't leave NR to the computer without using dark frames.

[g dan mitchell]

Agree with Mark U about the noise reduction - this is a different sort of noise than you'll see on more typical exposures.

You will see some solid blue, green, or red pixels that will stick out like the proverbial sore thumbs. Typical software post-

processing noise reduction software won't do a very good job of handling this - the dark frame approach is your best bet.

 

I do not use battery grips, so my earlier answer was in the context of no grip.

 

Dan

[sarah_fox]

Wow, can a digital take that long an exposure without the image being garbage?

 

If it's going to work, you need to bring your camera's circuitry up to a stable temperature for the shot, or else the dark frames might not do you much good. You might start out with a 15 min exposure to be discarded -- just to warm the sensor. Then shoot a 45 min (!) dark frame, as Mark suggested. Then the real exposure. Then another dark frame.

 

One precaution: I don't know what happens during a long exposure when the camera runs out of power. Does it terminate the exposure and write the data while there is still adequate voltage and then shut down gracefully, or does it simply run out of power and die? If the camera only monitors voltage between exposures, then it could be the latter. The consequence could be an over-depleted/damaged lithium battery and/or a corrupt CF card. Even worse, the camera could go schizoid and corrupt its own operating system. (Programmers don't always think about these things, so we shouldn't make assumptions.) It might be good to give Canon tech support a call about this. If they tell you wrongly, then surely they would swallow the cost of replacing the battery and/or restoring the operating system.

 

Use a fresh CF card for each shot, rather than risking the loss of your photos. Doing your own dark frames manually and then recording each dark frame separately would be a way to minimize the chances of data loss.

 

Here's an idea for you, but I don't know if it would work: The grip has two battery compartments. You might be able to charge one battery while using the other. Carefully insert the fresh one and then eject the depleted one. You'll get a bit of tripod motion, but if you're careful it shouldn't be too noticeable. Using this method, you should be able to run indefinitely. One caveat: I don't know if the camera would shut down when the grip's battery door is opened. (Anyone know?)

[Jeff Lear]

Just tested it and it does shut down the camera when the battery grip door is opened.

[kahkityoong]

The 5D has no problems with 45 minute exposure. From memory the longest one I did was 90 minutes. I don't see why you

would use ISO 50 for startrails. No better noise control that ISO 100 and you'll end up more underexposed and get more

noise.

[g dan mitchell]

I'm with Kah Kit Yoong on the ISO question. There is almost never a reason to use the iso 50 setting, and it will certainly

not improve the noise situation at all. Basically, f/8 and ISO 100 should work well for star trails. You could bump to ISO

200 and shorter the exposure by half.

[mark u]

The brightness and number of star trails recorded is determined by the ISO/aperture combination used. The length of the trail in an individual capture is determined by the exposure time. Multiple captures can be added together to produce longer trails.

 

Minimising noise in the dark sky background is not straightforward as the first link I provided should indicate. With long exposures there is an element of noise that increases with exposure time, an element that increases with sensor temperature (which itself increases with longer exposures and also with repeated time exposures even if the ambient temperature is constant). This is why it makes sense to use two dark frames - one at the beginning of shooting and one at the end. You can use a (weighted) average of these dark frames to subtract the noise from your actual exposure(s). The optimal ISO and exposure time depends on ambient temperature. Essentially you would need to do the same testing that Roger Clark did on a 10D to determine the best way to go on a 5D.

[david_e._starr1]

All good advice, thank you all. But there's still something I don't understand.

 

I've tested it with the 40D, and it doesn't seem to have the problem mentioned earlier, but the 5D might. The whole thing where, if you take a 10s exposure, it'll take 10s to process, and if you take a 5min exposure, it'll take 5min to process, that stuff. The 40D doesn't have that delay, but I guess the 5D does?

 

And if so, if I were to take a couple dozen shorter long exposures and compiled them, wouldn't the trails be more like dashed lines? If half the time, the camera would be processing, theoritcally the star trails would consist of a trail that is... say, an inch long, with a gap that is another inch long, followed by another inch-long trail, so on and so forth.

 

Or am I mistaken?

[mark u]

See p 96 and p 151 of your 5D manual. Set noise reduction off, but capture your own dark frames (lens cap on, aperture set to f/22 or using the body cap rather than a lens) of the same duration as your exposures - as suggested, one before and one after your main shot(s). That way you can shoot with a minimal gap between frames - just 1 second using the TC 80 N3 for example. You might also be interested in this software:

 

http://www.tawbaware.com/imgstack.htm

 

if you don't have a suitable way of mimicing what it does.