MORE noise in RAW?? - DPChallenge Forums

Canon EF-S 18-55mm f/3.5-5.6 IS

09/07/2005 11:46:55 AM · #1

I was thinking the other day (my 1st mistake), since RAW is virtually unprocessed by the camera, should we expect a little moer noise? This wouldnt be a big deal b/c we take it out during post-processing, just a question I have.

Konador

Canon EOS-500D Rebel T1i

09/07/2005 11:51:09 AM · #2

I would think less noise as there is no sharpening, but I could be wrong?

Mattel Barbie Photo Designer Digital Camera

09/07/2005 11:54:09 AM · #3

I thot the same thing..and the more I think about it the more I don't know.

nsbca7

09/07/2005 12:10:36 PM · #4

Originally posted by Konador:

I would think less noise as there is no sharpening, but I could be wrong?

There is also no compression. If you are worried about noise shoot RAW.

Bear_Music

Samsung Galaxy S24 Ultra

Sony 24-70mm F4 Vario-Tessar T* FE OSS

09/07/2005 12:32:48 PM · #5

At the most fundamental level, the noise in an image is independent of the format used. For any given sensor, a given combination of ISO/exposure will produce "x" degree of visible noise, and that's built into the system. Some cameras handle this better than others, higher ISOs always have more noise, etc, but it is what it is. The question is how you deal with it afterwards.

Speaking of shooting JPG, one way to deal with it is to enable "noise reduction" in the camera. There are tradeoffs in terms of sharpness/acuity, but noise reduction does have a visible effect.

Now, in my 20D I've noticed that when I shoot RAW and open the image in the RAW editing program it is processed to the parameters I have the camera set for. In my case that's low contrast, low sharpening, low color saturation, whatever WB I have dialed in, etc. I also have adjustments I can make to increase, decrease, or otherwise adjust all these settings.

What I DON'T see is any adjustment for noise reduction; it doesn't seem to be adjustable after exposure.

I deduce from this that the camera settings for noise reduction are either not applied to RAW images (unlike WB, sharpening, contrast etc, which are, but are adjustable in PP) OR are applied-by-unchangeable.

I'd be curious to know which is the case. It may be that because I am working with Canon Capture One (the only RAW editor I can find that works with Windows Me) I am missing more sophisticated levels of adjustmnent, I donno...

Robt.

colema19

Canon EOS-20D

09/07/2005 12:49:07 PM · #6

jpeg compression will cause something of a smoothing effect too, perhaps what you are seeing as noise is just more sharp definition in the image which might be masked in a jpeg compressed image?

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

09/07/2005 02:41:47 PM · #7

Here's my understanding of the noise issue...
As Row-Bear posted, there is a basic amount of noise that is a characteristic of the sensor and electronics used. Subsequent processes such as analog-to-digital conversion, demosaic/bayer interpolation and compression (for JPEGs) can add noise. Noise canalso be removed via a combination of hardware or software algorithms. The end result is that each camera design (in fact each specific camera) has a unique "noise signature" that is a result of the total system. To a degree, user settings can also affect this noise signature.
With respect to RAW vs. JPEG noise, in theory you can get cleaner files from a cam using RAW *IF* you use the additional dynamic range that RAW provides, that is, you "expose to the right." What "expose to the right" implies with RAW is that some highlights actually get "blown" according to the luminance histogram (which judges what is blown out by whether it would be blown in a JPEG file) but are recovered by pulling down exposure in RAW conversion. The end result is that noise is decreased along with the "signal" and the final image is cleaner. It is a significant departure in shooting mentality, since you are NOT shooting to exactly duplicate the final look you want; you're shooting to maximize the quality of the final image, and these are different objectives.
For like-exposed images, there is little difference in noise in RAW vs. JPEG images, provided that the compression level of the JPEG image does not add artifact that is perceived as noise.
As a final note, there is "luminance smoothing" implemented in some RAW converters, and this is a type of noise reduction.

Canon EF 24-105mm f/4.0L IS

09/07/2005 04:13:42 PM · #8

Fritz...did i understand you correctly? I have read on Luminous-Landscape and many other sites to UNDER-expose using digital and recover the shadows b/c they say once highlights are blown they are blown. Is that only in .jpg and if I'm shooting in RAW I should OVER-expose? If so, how much should I over-expose? 1/2-2/3 stop? Thank you to everyone for the help.

rjpat

Canon EOS-20D

09/07/2005 04:40:37 PM · #9

Kiro, check out this link, it explains what they are talking about.

Expose to the right

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

09/07/2005 04:42:46 PM · #10

Originally posted by kiropractic:

The advice to underexpose digital is really pretty crappy advice. It is true that if you are shooting JPG you need to be careful with blowing highlights (or blowing individual color channels on saturated subjects). Shooting RAW allows 1/2 to 1 stop of additional "headroom" so you can move the histogram to the right that amount and pull the exposure back in conversion, however like any format, if you overrun the dynamic range of the capture device, you'll still have irrecoverably blown highlights. Experience is the best teacher here. An RGB histogram on the camera helps greatly, but is only available on higher-end equipment (it's one of a raft of reasons I am buying the 5D) and still gives an indication of blown highlights based on a JPEG file, so you need to judge by how much you can blow them. Like trying to judge how fast you can drive without getting a ticket, LOL.
Bottom line, it's not possible to generalize that we need to "overexpose" by a certain amount. If shooting a low-key subject, you might be able to "overexpose" the intended final look by 2 stops, then pull it back. If shooting a high-key subject, you might be exposing spot on, or possibly being conservative and slightly underexposing to ensure the highlights are held.
It's unfortunate that camera histograms can mislead, especially luminosity histograms, however they are still the best tool that we have, and once you learn to always use the greatest allowable level of exposure, you'll be rewarded with a significant decrease in shadow noise. It's never desriable to "pull up" shadows significantly unless there is no other choice.