Which produces least noise...

[pressld2]

...bumping up the ISO in camera or boosting the exposure in your RAW converter?

Personally I hardly ever shift my D70 away from its minimum ISO setting of 200 but this often means that I have to push the exposure a little (sometimes a lot! ) in RAW conversion. I keep thinking about running some tests to see which produces the least noise but haven't got around to it yet. Just wondering if anyone has already investigated this and has an opinion to offer...

Dave P.

BTW for RAW conversion I used to use RawShooter Premium and am now using Adobe Lightroom. With either product I'm seeing visible noise if I push the exposure more than about +1 EV.

[Kev Lewis]

Originally Posted by pressld2

...bumping up the ISO in camera or boosting the exposure in your RAW converter?

Personally I hardly ever shift my D70 away from its minimum ISO setting of 200 but this often means that I have to push the exposure a little (sometimes a lot! ) in RAW conversion. I keep thinking about running some tests to see which produces the least noise but haven't got around to it yet. Just wondering if anyone has already investigated this and has an opinion to offer...

Dave P.

BTW for RAW conversion I used to use RawShooter Premium and am now using Adobe Lightroom. With either product I'm seeing visible noise if I push the exposure more than about +1 EV.

Any unexposure in-camera will result in significant noise in the darker regions of the image when you correct it in the Raw convertor. You should always expose to the right on the histogram without blowing the highlights, this gives the sensor the maximum signal to noise ratio and minimises the noise produced.

Personally I think Aperture, Shutter speed and then Iso when I shoot. i.e what aperture do I want/need for the DoF, then what shutter speed and then what iso do I need to use to get the aperture and shutter speed. But it does depend on the circumstances and is almost always a compromise lol

[pressld2]

It's been chucking it down all day today and, being a fair weather photographer, I've been stuck indoors. So I decided to knuckle down and actually run some tests to look at the effects on digital noise of raising the camera's ISO setting compared with underexposing and then correcting in RAW processing.

Equipment used: Nikon D70 with Sigma 150mm f2.8 APO Macro lens set at f11, mounted on a Velbon Ultra Lux i F tripod. The lighting was a fluorescent desk lamp.

Software used: RAW conversion was done in Adobe Photoshop LightRoom v1.0 and files exported as 16 bit sRGB tiffs. These were sharpened using Unsharp Mask in PaintShopPro v9.01 with settings of radius: 1.00, strength: 50 and clipping: 5 then saved as jpegs at maximum quality.

This is my benchmark image, taken at ISO 200 and correctly exposed in camera with no adjustments made in LightRoom...



In the comparison sheets below the left-most samples are all taken from this image. I then took the same shot again at ISOs 400, 800 and 1600 but still correctly exposed. Finally I took shots that were underexposed by 1, 2 and 3 stops and then boosted the exposure in LightRoom to compensate.

This first comparison sheet is from an area with a lot of detail and a good range of colours and tones...



As you'd expect the noise increases with ISO, particularly in the shadows. The noise is not quite so obvious in the corrected underexposed shots but there is a big loss of shadow detail.

However, it's a different story when looking at an area of more uniform tone and colour...



I think it's pretty much neck and neck between the ISO 400 and the 1 stop enderexposed images, both of which show only a minor loss of quality compared to the benchmark. But after that I think the higher ISO is a clear winner over the RAW corrections.

All of which is a very long-winded way of saying that Kev is right - it's better to bump up the ISO if you have to than to try and rescue an image in RAW conversion.

Dave P.

[matt_xyz]

that's interesting, thanks for reporting those tests.

Matt

[glsammy]

Yes very interesting. More info to store away!

[Roy C]

For bird shoots on the 30D I rarely shoot below ISO 400 and very often shoot at ISO 800 but I always try to expose to the right which means that I do not introduce any noise at the processing stage. In fact I use spot metering and +2/3 of a stop compensation as standard.

[Jon]

I agree, I have also come to my attention that the nearer the captured image is to "correct" then the better the imago will be. Pretty obvious we would all chorus.

I have also been made aware of a couple of tips I am happy to pass on:

If you make any required adjustments in Adobe RAW as opposed to Photoshop - and you can get the image you want, then this image is likely to be of a better quality than if you go straight to Photoshop and make your corrections there. This is because you are dealing with the raw data as opposed to anything that has been processed in any way. I Know a TIFF is lossless and all that malarkey but if you can get the image you want in Adobe RAW as opposed to Photoshop the resultant image will be better.

Also if you need to crop and or resize the image it is best to do it in Adobe RAW, and if you do not need to go to Photoshop, apply the sharpening at Adobe RAW as opposed to Photoshop mask. If you foresee the need to use Phtoshop then it is best to reduce the sharpening to zero and then make your adjustments in Photoshop and finish with the Unsharp mask.

I am not for one minute suggesting you will not get a good result in Photoshop, or in any way implying they are not good enough, I am just relaying what I have been advised by professionals. I am just continuing within the spirit of attempting to achieve the best image from the data captured.
Hope this helps.
Jon