So, I have been taking some long exposure shots and I`m planning to do more of those as I will be receiving an ND 110 filter (10 stops) soon (jay!). Time to spice up those old beach photos!Alas, after 30 seconds of exposing, my camera seems to need at least that same amount of time to think/process/write/whateveritsdoing. I have been missing 90% of all the cool lightnings (ask Murphy). Is buying a new Compact Flash card going to solve this? I now have a 15MB/second UltraII and am aiming for the 60MB/second Extreme. I have a Canon 400D.This question almost seems too stupid to be true, but I have been fooled by promising specs before, and I'm not looking for just a faster upload to my computer.Any intelligent remarks on this?
Your camera needs **exactly** the same time following a long exposure in order to do the long exposure noise reduction. It has absolutely nothing to do with the memory card.The reason is that things like 15 seconds are like epochs for electronics, it's an extremely long time. The sensor gets electrically mucky due to leakage currents, which may be uneven. Bad cases show up as hot pixels, like little stars.Long exposure noise reduction works by taking a second shot for the same time with the shutter closed immediately after the first shot, then it subtracts the noise from the dark shot.If the time is really unsupportable, look through your cameras menus for the option to disable long exposure noise reduction. Of course your images may be worse, or they may not be, silicon production is always subject to continuous variation, you may be lucky and got a sensor that is well balanced!An intermediate technique is to take a single reference dark shot (like with the lens cap on), and then subtract that in PP. I know this can be done in RAW, but no idea how as I-ve never played with it (there's something to put on my list of things to experiment!).
Pr4ktic saidTime to spice up those old beach photos!
Mull of Kintyre,Oh mist rolling in from....
I am not sure on the Canon but on the Nikon it takes quite awhile for the camera to perform the long exposure noise reduction. Is that what is taking your camera so long? If so different memory won't have any effect.
Thanks for saving me 54 euro Ercolano. I`ll be sure to think about you when I spend that on my next 70 beers here at the beach (yes, Brazilian prices are awesome. the deliver the beer cold until in the water for that)Mull of Kintyre, man, that may have been the first videoclip I have ever seen. Although maybe Cliff Richard won that...
Are you guys sure? I just tested with my camera, and took a 30 second long exposure and as soon as the shot was taken, it was immediately ready to take the next one.. I did it 3 times in a row and I didn't have to wait. My card is a Compact flash (Sandisk Extreme III) 30mb/sec and my camera is the Canon 40D.
I'm with Eury on this one and it sounds like you've got "Long Exposure Noise Reduction" on.Bottom of page 103 in the User ManualAnd on a side note - I can't notice any speed difference between Ultra II's and Extreme III's, either in camera or downloading to PC when used in a 40D. (But I understand it could be quicker using a card reader with the PC, but I've never tried)
I`m sure I have LENR on, because I chose to do so. But now I will test to see the impact of setting it off.
If the noise with LENR is too bad, you might look creating the dark-frame yourself first and use some didicated noise reduction software (e.g. NeatImage) profiled from the dark-frame to do the noise reduction in PP. The software will set you back about the same amount as the memory card, but I find some cutting edge noise reduction capabilities are quite useful as it will make the higher ISO speeds on your camera more usable.
Eurydice saidAre you guys sure?
Absolutely. **If** you have long exposure noise reduction enabled then the camera will take two shots of the same length, once with the shutter open, and once with it closed. All cameras are like this when doing long exposure.Of course if it is turned off there is no difference to any other shot ;-)As far as the time taken to record to the memory card is concerned, there is no difference in write speed for a change in shutter speed, in fact the image is first captured into an internal buffer before writing to the memory card.The reason for all the confusion (and this misconception that long exposures take a long to to write is quite common), is because during the second exposure the camera blinks the busy lamp, just the way it does when writing to the memory card. It would be clearer if the camera stated on the display "please wait while noise reduction calibration takes place" or something similar. Unfortunately the LCD display on just about all cameras is placed back to back with the sensor, and the second NR shot has to be done under as similar conditions as possible to the original shot, i.e. with the LCD off to reduce noise (and heat disturbance) from that.If you find the wait anoying, it's worth playing around to see how much effect it actually has on your camera, long exposure noise problems vary at random; two identical cameras could yield quite different results.
VoidPointer saidyou might look creating the dark-frame yourself first and use some didicated noise reduction software (e.g. NeatImage) profiled from the dark-frame to do the noise reduction in PP.
Does this work for long-exposure noise? I thought NeatImage, etc. just take out the noise pattern that is inherent to a given sensor design. Whereas the "long-exposure" reduction handles the "hot pixels" that occur in a basically random fashion that's unique to the specific sensor in your individual camera. Can NeatImage also take out long exposure noise? Would be nice to do this after-the-fact so that you don't have to sit out on a cold night waiting for the camera.
+ in reply to...
Since you can create noise profiles that are specific to your sensor at specific ISO settings and exposure times, you should be able to create a profile from a black frame at a given exposure/iso time and use that as a profile to run noise reduction on your long exposure images... I have not tried it and have patiently waited for the camera to do its thing. I will give it a try and post results.
Hot pixels are the obvious ones, but could easily be picked out by hand using the healing brush.Truth is you have a whole noise floor, mostly subtle but nonetheless present. It should be possible to subtract a sample noise floor shot from an unfiltered shot, but the form of the dark noise is not constant. This is why cameras do two shots back to back, it will give the best results.If time constraints you to not use LENR, then a single reference black shot taking in the middle of the shoot and applied in PP is probably better than non at all, but taking one reference and expecting to reuse it in any time frame, as you might do with a custom WB, will probably be not so effective.Applying correction using a dark reference shot that's significantly different from the conditions under which the shot was taken could make the noise worse.
Bummer, I can't test it right now. My Pentax has two options for LENR: Auto and On. No way to turn it off entirely.As far as the reference frame is concerned. Just subtracting it won't help. Noise is random, so the noise in the reference frame will not match the noise in the actual photo pixel-by-pixel. It will however have the same statistical properties (noise profile) and thus, a noise reduction software that can build a profile from a reference image that includes mostly noise can help you.