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theMusicMan
24th July 2009, 10:53 AM
Hi All

I have recently purchased some fabulous new filters... an ND8 and an ND4 (both Cokins, to fit my current set up) and last night went out to try them out for the first time. They are excellent... however, for long exposure shooting - I am right at the bottom of the ladder here and have an awful lot to learn. It's really not as easy as it seems, and it really makes you think about everything.

Here's my first question: How do I best deal with long exposure noise...? I notice that as I have NR turned on on my E-3, when I take a 60 second shot, the camera opens the shutter and exposes for 60 seconds, and also then shows as 'busy' for a further 60 seconds as it deals with the noise via a black exposure (I think that's what it is doing). However, the resulting images I see are still very noisy, even at ISO100.

Is this right...?

Should I turn of noise reduction 'in-camera' and deal with the noise in post processing...? Are there alternate solutions I should consider...?

Any pointers from the experts greatly appreciated as I embark on this new learning curve.

Thanks all.

Ian
24th July 2009, 11:29 AM
Dark frame noise subtraction is very effective at eliminating inherent sensor noise, so don't switch that off, but as you have discovered it does double the overal time that the camera is busy.

Some residual noise will remain, and this can be further cleaned up in post processing.

Ian

theMusicMan
24th July 2009, 05:11 PM
Thanks Ian - I'll leave it on then and when I get shots that I am happy with I shall also apply some additional post processing noise reduction.

I was quite suprised with the amount of noise though, especially as the images I took were at ISO100.

Also - I wanted greater than 60second exposures but the E-3 only goes up this far. Need to use bulb mode when I get a manual cable release as the IR one I have doesn't keep the shutter open when you keep your finger on the trigger.

How is this best done...? Is it with a cable release...?

Archphoto
24th July 2009, 05:18 PM
A cable release can be had at ebay for cheap, there are several sellers offering them for 1/10 of the price of the Olympus one and that are as good.

I got one for my E410/E520 and it works as it should.
There is a version for the E3 aswell, try # 260359110321

Peter

photonutter
24th July 2009, 07:15 PM
A couple of other things to check, even if your shooting raw, is saturation and contrast. Stick with natural or muted mode, certainly not vivid, you'll get higher saturation with the longer exposures anyway.

photonutter
24th July 2009, 07:58 PM
I also use the RM-1 infrared remote which will open and close the shutter in bulb for longer exposures. Star trails by any chance?

Ian
25th July 2009, 09:22 AM
Noise is all about the consistency of the values recorded in each photosite. Each photosite is a well that fills up with electrons (or an electrical charge) that are released when a particle of light (photon) strikes the well. In theory, if the same number of photons (brightness) is received by two wells on the sensor, then the charge that builds up and is read by the analogue to digital converter should be identical. Under normal bright conditions this is more or less what happens.

But when there is a much longer exposure, there is time for the charge to leak away somewhat before it is read, or even become artificially increased (maybe by leakage from an adjacent well). These problems are exacerbated by heat that builds up the longer the sensor is active during an exposure.

This means any small inaccuracies in the capability of each well are amplified. A high degree of these inaccuracies are constant. So if you use Noise Reduction mode, after the image has been taken the camera will reset the sensor, and then switch it back on for the same period of time that the exposure was originally set, any charge that builds up will be known to be not part if the image exposure. You can then deduct the values in each pixel from the second dark reading the data already read from the sensor to cancel out sensor noise.

This makes a big difference for long exposures, but won't eliminate noise 100%, even at the lowest ISO.

One tip: if your subject is mostly dark and there are no highlights that can be recovered anyway (like bright spot lights at night, for example), you could try using the Low Key gradation mode. This is especially relevant if you shoot JPEGs, but even in RAW mode the exposure will be altered and may make it possible to produce better results from RAW.

Ian

Ian
25th July 2009, 09:46 AM
Thanks Ian - I'll leave it on then and when I get shots that I am happy with I shall also apply some additional post processing noise reduction.

I was quite suprised with the amount of noise though, especially as the images I took were at ISO100.

Also - I wanted greater than 60second exposures but the E-3 only goes up this far. Need to use bulb mode when I get a manual cable release as the IR one I have doesn't keep the shutter open when you keep your finger on the trigger.

How is this best done...? Is it with a cable release...?

Use the Bulb Timer setting in the Exposure tool menu. I don't have an E-3 with me at this very moment, but an E-620 I do have here can be set to open the shutter for up to 30 minutes. You don't need a wired remote to keep the shutter open in bulb mode. If you have the infra red remote RM-1, in bulb mode pressing the W button opens the shutter, and you don't need to keep it pressed. You can then wait for the timer to run to the end, or press T to close the shutter when you wish.

Ian

Nick Temple-Fry
25th July 2009, 10:36 AM
I don't intentionally take such long exposures as John is aiming for, but on occaisions in shooting inside churches for hdr I can get exposures upto 40 seconds (at iso100) and other than a scatterring of hot pixels there is not an issue with noise.

The differrence is of course the exposure, the images are (in conventional sense) largely overexposed (for the purpose of pulling details out of the shadows). If John is shooting long exposures of scenes that are going to remain predominantly dark then he is going to fall foul of signal to noise ratio. As noise is random ('ish) it is unlikely that dark frame will generate exactly the same value for subtraction, so any residual will be noise; if the scene is dark then the result will be the noise is the predominant signal from that part of the image.

I wonder if John needs to look carefully at the exposure of the images he has taken, and maybe use a combination of grad and non grad filters to get a better overall exposure.

Just idle thoughts delivered in ignorance.

Nick

photonutter
25th July 2009, 12:56 PM
You could also take multiple exposures at the same exposure setting and layer them in photoshop to reduce random noise. The ony problem there is if your getting light trails from either stars or moving traffic.

Archphoto
25th July 2009, 01:08 PM
Noise in night-shots, or any long-exposure shots, can be diferent between camera's: with my E410 I have verry little, with my E520 I have a lot.
And that at the same settings of 100 ISO at side by side testing.

I ended up using the E410 for my long exposure shots and use the E520 for what it is good: where I need IS and noise is of a lesser issue.

Peter

theMusicMan
28th July 2009, 04:42 PM
Use the Bulb Timer setting in the Exposure tool menu. I don't have an E-3 with me at this very moment, but an E-620 I do have here can be set to open the shutter for up to 30 minutes. You don't need a wired remote to keep the shutter open in bulb mode. If you have the infra red remote RM-1, in bulb mode pressing the W button opens the shutter, and you don't need to keep it pressed. You can then wait for the timer to run to the end, or press T to close the shutter when you wish.

Ian
Great info Ian, I didn't know that, thanks.

I wonder if John needs to look carefully at the exposure of the images he has taken, and maybe use a combination of grad and non grad filters to get a better overall exposure.

Just idle thoughts delivered in ignorance.

Nick
Possibly Nick, though I did use a combination of grad and non grad filters for these shots.
You could also take multiple exposures at the same exposure setting and layer them in photoshop to reduce random noise. The ony problem there is if your getting light trails from either stars or moving traffic.
I shall try this next time I am there photonutter, thanks.

ringneck
30th July 2009, 09:22 AM
Fantastic thread ...as always I have learned SO much ......and on an issue I have had probs with myself(amongst many others).

Well done all
Keith*chr

JerryE-1
30th July 2009, 10:11 AM
I've found Neat Image does a good job on higher ISO E-1 files. You can download a free version that's limited to 8 bit and high quality jpeg output that's a stand-alone application. The more advanced 16 bit, TIFF output stand-alone and Photoshop plug-in versions do cost, but are quite reasonably priced.

Cheers,

Jerry.

Wreckdiver
30th July 2009, 11:34 AM
A cable release can be had at ebay for cheap, there are several sellers offering them for 1/10 of the price of the Olympus one and that are as good.

I got one for my E410/E520 and it works as it should.
There is a version for the E3 aswell, try # 260359110321

Peter

The subject of these cheap remotes has appeared on this forum several times before and the opinion I get is that they cause problems, including damaging the socket on the E-3. I use the Oympus RM-CB1 and although expensive, is the best option in the long run.

Steve