# Rebel XSi image noise



## ShootAndSpin (Apr 15, 2015)

I'm fairly new to the XSi, which I realize is a fairly "entry level" DSLR. I used to shoot RAW images with the original digital Rebel and had decent results with little-to-no digital "noise". I noticed with the XSi that I tend to be getting a lot of it in my images. I realize it's common to get more when shooting in low-light situations, but I also get colored artifacts when shooting in daylight at ISO 200 at 1/100 in Manual mode, which never seemed to happen when I used the original Rebel DSLR. Is this a common problem with this camera, and if so do you have any suggestions to remedy this issue? I use Photoshop, but you can only do so much with the noise reduction filter.


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## waday (Apr 15, 2015)

Someone else may be able to provide more technical information, but I can absolutely understand where you're coming from as an XSi owner.

Post a few shots showing these problems and the folks here can help determine if it's a settings/light issue or a camera issue.

The biggest thing I've found that will help is to make sure you have good, sufficient lighting. Not lighting that you think is good enough, but the correct amount for proper exposure of the photo.

It's funny, I look back at photos that I took a few years ago (or even a few months ago, haha) that I thought were fantastic. They were almost always underexposed or way overexposed. I've just come to terms with the fact that I will have some amount of noise in my photos when shooting in less than stellar light. Yes, Photoshop and Lightroom can remove a good amount of it, but there's always the balance of removing too much or leaving some in the photo.


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## KmH (Apr 15, 2015)

Because a digital camera doesn't work like our eyes work we have to consider the dynamic range of the scene we are shooting compared to the dynamic range the sensor in our cameras can capture.
The camera needs quite a bit more light than our eyes do.
With a DSLR we usually also have 3 or more light metering modes we can choose from - Spot, Partial, Center-weighted, Matrix/Evaluative.

Understanding Camera Metering
Understanding Image Noise
Understanding Dynamic Range
An exposure control technique we can use to minimize image noise is known as Expose-To-The-Right, or ETTR.
To-The-Right means to the right on the image histogram.
We expose for the highlights in a scene and let the shadows take care of themselves.
Optimizing Exposure - Luminous Landscape
ETTR
Exposing to the Right - Digital Photography School

*Tones & Contrast*

Understanding Histograms, Part 1: Tones & Contrast
Understanding Histograms, Part 2: Luminosity & Color
Using the "Levels" Tool in Photoshop
Using the "Curves" Tool in Photoshop
Understanding Image Posterization


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## TCampbell (Apr 15, 2015)

I'm not sure what "colored artifacts" are without looking at sample images... but be aware that if you shoot JPEG, the images go through the JPEG algorithm which compresses colors and "normalizes" pixels that seem to be "nearly" the same color value so that they just are the same color value.  But when you have areas with gradually changing tonality, you can notice digital artifacts where the image suddenly changes from one level of tonality to another one.  You wouldn't see this if the image were displayed using a non-lossy format and it can be reduced with JPEG by setting the lowest possible compression levels.

Edit:  I see Keith's note above has a link of "Posterization" -- which is what I'm referring to.  Take a look at that link and tell us if this is the sort of thing you are seeing your images when you refer to "colored artifacts".


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## ShootAndSpin (Apr 17, 2015)

It doesn't seem like posterization to me. There's pixels that are completely different colors from the pixels surrounding them, but it usually only occurs in the darker areas of the images. Not underexposed, but darker than the rest of the image. For example, it tends to happen around "Zone 3 and 4". (Sorry--I was taught to use the Zone System when I was in school. ) I apologize for not having any samples to show right now. I'll be out of town for a few days, so I don't have access to anything at the moment. A friend of mine suggested I tried using my hand-held light meter instead of relying on the one in-camera because, while the images I'm referring to are usually exposed fairly well, I do sometimes have to tweak the Fill Light and Recovery settings in the RAW editor screen. I could just continue shooting with my older Digital Rebel, but the RAW files produced with it aren't recognized by my newer version of Photoshop.

I'll shut up now. I'm just rambling "out loud."


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## Tinderbox (UK) (May 18, 2015)

I have downloaded a few sample raw`s and they seem all right, I like correct underexposed photo`s to see what noise is introduced, some sensor have not just noise, but colour noise which is a pain.

The Noise in the corrected XSi photo`s i checked seem fine to me, but maybe i am more tolerant. 

We really need a sample to see what is wrong.

John.


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