jimy444 said:
Hi Guys
i am facing a problem when using my 5d mark 2 during night shots
I am shooting at 5 - 10 - 30 seconds and bulb and it is taking as much time for the picture to display on the screen/finish processing as the exposure time
example if i set the exposure to 30 seconds it takes another 30 seconds for photo to appear
and the buffer is going full and making me wait after couple of shots.
Imagine doing it on long exposures, 100 secs each.. i can only shoot couple of shots and it will make me wait to finish precess before i can even shoot another one.
is this normal ?
are you facing such problems, i tried with a friends 5dmark 2 and it is going much faster. even with a 200 seconds exposure the photo is appearing the second the shutter closes, and it is a big problem as i shoot night skies and scenery to wait that long for each photo...
The increased time is the built-in camera
Long Exposure Noise Reduction (LENR). It exposes what is called a Dark Frame after the light frame, and that frame is used to subtract noise (assuming it works...in-camera LENR does not always work.)
If you are doing night sky astrophotography and want low noise results, it is better to handle noise reduction on your own. You can take your own dark frames, as well as bias frames, in addition to light frames, and combine them all with a tool like DeepSkyStacker. DSS will use multiple light frames to maximize SNR, and use a properly combined dark frame and bias frame to subtract the noise.
Light Frames are the full color exposures of the night sky. It is best to have as many of these as you can. A single light frame will be very noise, poor in contrast, low in SNR, and otherwise barely sufficient for a night sky photograph. Stacking two light frames produces better results with higher contrast, but you will still have a low SNR. It is best to shoot at least 20 light frames or more of the same stellar object to maximize SNR.
Dark Frames are exposed the same as light frames, only with the lens cap on. By "the same as light frames", I mean...EVERYTHING has to be the same. Shutter, Aperture, ISO, AND temperature. The temperature matters her because it affects noise. If you are shooting the sky on a very cold night, dark current will be lower than on a normal night, and noise will be lower than on a normal night. You can expose all dark frames after the entire sequence of light frames is done. It is best to have 16-20 dark frames to produce a master dark frame for that particular shoot. If you end up shooting 40, 60, 80 light frames, you still only need to have 16-20 dark frames.
Bias Frames are created at the fastest possible shutter speed, and the same ISO as the light frames. It does not matter what the temperature is. Again, it is best to have 16-20 bias frames to produce a master bias frame for that particular shoot.
Once you have a set of light frames, dark frames, and bias frames, you can stack them with a tool like DSS. Just give it all the files, and it will take care of the rest. It'll produce master dark and bias frames for you from their individual frames. It will then process the light frames...align them, apply the dark and bias frames, then stack them to produce a single, low-noise, high SNR night sky photo. Once you have the initial night sky photo...you are pretty much on your own to tweak the final outcome (which is actually quite a pain with DSS, you might end up better off by exporting the default output for tweaking in another program.)
The results of the above method should be far superior to single-shot exposures of the night sky, with or without in-camera LENR.
