Rebel XT - high noise at 200-400?

[Hobbit]

Hello everybody,

I own XT for about half and year and generally fond of it. But... there is something that I can't figure out.

When I do pics on 400 I frequently get fairly hight noise in shadows and half shadows. E.g. even peoples bodies and faces are getting noisy if they are a little out of focus. Yes I mostly can clean up this noise with NeatImage but picture is then becoming usable only for 8-10 inch print.

I also get some noise even at 200. For instance the relatively dark clouds got noisy when I shot sunset. The noise can be seen fairly well and especially on 100% magnification.

Also - I noticed that when I am making picture in green zone the camera is setting ISO at 400 always. Didn't see anything describing this "feature" in the manual.

Now I want to know if there is something wrong with my camera, or my photography technique or this is how it is supposed to be by default with Canon Rebel XT? :confused:


I wonder if anyone experienced the same problem and may be you can tell me what would be resolution?

Best regards :)

Michael

[24Peter]

Michael - you can get noise with the XT (or any digital camera for that matter) even at ISO 100 if the image is underexposed. What you want to do is make sure you have enough light. But even in otherwise well exposed images I sometimes see noise at ISO 200. Not enough to bother with noise reduction software but it's definitely there. So it's no wonder you're seeing noise at ISO 400 in the shadows. Try adding more light (flash, reflector) to the image and see what happens.

Let us know. :)

[Hobbit]

Hello Peter,
Thanks for reply!

Well - yes you are partly right. I looked at number of pictures and majority of them have noise in the shadows and half shadows...
However- shadows sometimes are necessary element of the picture and when I see it on the 100% I see no noise on the well exposed person's face and noise where part of the body is in shadow or half shadow. So the overall exposition is fine -exactly what I wanted, but the noise is there...And sometimes I have a clearly dark underexposed image and still practically no noise at 400. As well at 100 I practically don't see any noise anywhere...shadows or not.
So this looks a little strange for me. Something like inconsistent behavior.


Best regards,
Michael

[coldrain]

Noise also gets worse the longer an exposure takes, so that may influence the results you are seeing too.

[Hobbit]

Well, I would expect it on long exposures and I would not complain to have it at 800-1600.
In my case the image is getting partly noisy on 1/250, f/10 , ISO 400 for instance.
Or this one for instance was shot at 1/80,f/11,200 with 18-55 EF-S wide open.

[Dawoofo]

What lens or lenses do you use, Hobbit?

[TheObiJuan]

I never had a problem with noise on the 350D or KissDN at ISO 400 or 800 when the images were correctly exposed. Sometimes there was a higher level of visible color noise that was EASILY removed with a PS mask. This left the image virtually flawless, not like it had been smoothed.
Is it feasible to post some crops of the noise with exif info?

[aparmley]

I'm with Obi on this one. . . ISO 1600 - straight out of camera.

http://parmley.smugmug.com/photos/46098962-L.jpg

[Hobbit]

Hello Dawoofo,
I am shoting with 18-55 EF-S and 50 f/1.8. 18-55 has fairly strong distortion at wide angle (you can see it on the image) otherwise it is O.K when you set it to sweet spot. 50 f/1.8 has not so smart AF in low light but cool optics.
I do get noise issue though with both of them.

Obi and aparmley,

Here is the crop from the image above. If you look at the building especially at the lower part in shadow you will see it. Obviously this image is easily printable at 8 x 10 - but if I magnify it to 100% noise is seen...

As to 1600 - yes I made few shots on 1600 several times and those are good as is up to 1024 X 768, cleanable with NeatImage or other soft if you want them bigger. Furthermore some shots I took at 400 are fine - no visible noise.

This is exactly what I am trying to figure -if there is problem with my unit or I am doing something wrong. If last may be some of you guys can help me by telling what am I doing wrong...

Thanks a lot guys!

[24Peter]

Well I see what you're talking about (i.e., you're not crazy:) ) It might be a little more than I would expect at ISO 200 but then again you're reaching deep into the shadows of an otherwise bright scene (f11). You may want to send the camera in just for peace of mind, but honestly what you're describing doesn't scream that your camera is faulty.

[Hobbit]

Thanks Peter,

I will probably post few more shots and crops here - I want to see if you guys would see any pattern, abnormality and then may be really send it to Canon.

[aparmley]

I don't see anything in that crop of the building that would lead to me thinking your camera had a noise problem. If you want to pixel peep you are going to see noise, no doubt about it. Is what is represented in your image cause to get worried - No. In fact, I thought that image looked pretty clean. Just me, or just my monitor at work? IDK - I really didn't see anything that looked out of the ordinary.

[Hobbit]

aparmley thanks!

I looked through the monitor at work too and it is different from what I see at home. So may be I need to have a look through yet another one. On the other hand even at my work I do see some noise...

anyways I guess that it it not easy to judge from 1 pic. I will post tonight few more.

Can I ask you another thing? with 18-55 is it normal to have geometric distortion of the scale I have on the same image wide open?

[coldrain]

Yes, that distortion for a lens like the kit lens is normal. Wide angle does that, you are closer to the bottom of the buildings than you are to the top of them. Also some barrel distortion is involved, probably, but that is not the biggest part of it.

You will always be able to see some noise when you try to look for it in dark areas that have not much structure, no matter what camera you have.
Even large format digital cameras show noise, I saw some samples of a mamiya and the noise was worse than an entry DSLR like your 350D/XT or a D50.

[Hobbit]

Well I see what you are saying - so the distortion is expected. Well I guess I will have to get better lenses for wide angle when my budget allows this :)

As to noise- again I see what you are saying - the question is whether the noise is abnormal in my case.
Below are few pics with crops from them. Please let me know your opinions - if the noise is higher than it should be at this ISO and exposure.

[cdifoto]

I think you're just being paranoid. Part of the problem is you're using a mediocre lens and showing us primarily OOF areas. The lens is not only mush at the edges, it's difficult to distinguish softness from shallow DOF from noise.

I can tell you right now that my L lenses show less "noise" because they're sharper all the way through compared to my kit lens which looks noisier because it's not a sharp lens except in the center.

Go shoot.

[Hobbit]

That is why I want the opinions. I get though same results with 50 f/1.8.

[cdifoto]

That is why I want the opinions. I get though same results with 50 f/1.8.


The 50 1.8 is a good lens but it's still not a stellar lens. It's definitely no L. It's possible your kit lens and your 50 are fine and you're just confusing shallow DOF with noise. It's also possible that you're underexposing. It's also possible you're expecting too much from an entry level dSLR. It has good ISO performance but it's not a 5D or 1Ds Mark II.


Go shoot.

[Hobbit]

Hm... well- I guess you are not right...but you are right:)
I use currently at home 19 inch LCD. There is noise on that screen...At work I use 17 inch Dell monitor set on 1280X1024. There is no noise - exactly shallow DOF and other things.
So I do see noise on my home screen, but you possibly see only noise, out of focus pic on yours...

[aparmley]

Don - where did you come across this information about lenses being the cause for digital noise? This thread here is the first I've heard of it. Am I totally lost. I am no expert on noise but I certainly have read many times over the common causes and not once heard of the lenses being blamed for making it worse or keeping it to a minimum.

Anyway Hobbit - I don't have any Ls and don't have any issues with noise unless I am forced to underexpose to keep my shutter speeds up - in which case Neat image gets the call and it always comes through for me on the default settings.

be that as it may, I just don't see any cause of concern on your part. If you are really feeling sour about it all return the camera and try another. If thats not possible. Then maybe sending it to CPS for a look might ease your mind. I don't know what else to say here.

[cdifoto]

Don - where did you come across this information about lenses being the cause for digital noise? This thread here is the first I've heard of it. Am I totally lost. I am no expert on noise but I certainly have read many times over the common causes and not once heard of the lenses being blamed for making it worse or keeping it to a minimum.

Anyway Hobbit - I don't have any Ls and don't have any issues with noise unless I am forced to underexpose to keep my shutter speeds up - in which case Neat image gets the call and it always comes through for me on the default settings.

be that as it may, I just don't see any cause of concern on your part. If you are really feeling sour about it all return the camera and try another. If thats not possible. Then maybe sending it to CPS for a look might ease your mind. I don't know what else to say here.


I'm not saying one lens causes noise where another would suppress it. I'm just saying, based on personal experience, that the quality of the OOF areas (not bokeh since bokeh is the background & lights not just blur) can sometimes look like noise when it isnt. My kit lens doesn't render blurred backgrounds very nicely and it could be confused with noise. It's just mush in some areas. Poorly defined areas (be they in focus or not) can be confused with being noisy, when in fact they aren't.

Compare that with any of my other lenses, and the OOF areas at any ISO look nicer...and the noise is there but not as bad because of how well those OOF areas are rendered.

Just my 2 cents.

[Hobbit]

Could you then please post few samples/crops of your OOF/noisy shots made with 18-55. And may be also something made with L lenses?
So I would stop being paranoid and start dreaming of 70-200 L f/2.8 IS ?

;)

[cdifoto]

Could you then please post few samples/crops of your OOF/noisy shots made with 18-55. And may be also something made with L lenses?
So I would stop being paranoid and start dreaming of 70-200 L f/2.8 IS ?

;)

I'd have to have the same image taken with both lenses and I don't have one. Not to be rude, but quite frankly I don't care to put the kit lens back on my camera.

I'm posting my observations, plain and simple. I don't really feel like going through the trouble of a scientific test. You're expressing your concerns about noise and I'm telling you why I think it might seem worse to you than it really is.

[Hobbit]

Well guys thanks everybody.

aparmley - special thanks for mentioning monitor. This I guess was a keyword :)

I looked at the 19-in CRT at home 17-in CRT at work and images are clean, no trace of the noise on 19-inch and on hight magnification it looks like fine (e.g. yes may be not focused somewhere but this is what I expected- not noise )

So thanks again everybody and ... don't buy cheap LCD monitors :) Mine is going back to the shop!

[TheObiJuan]

I don't see anything in that crop of the building that would lead to me thinking your camera had a noise problem. If you want to pixel peep you are going to see noise, no doubt about it. Is what is represented in your image cause to get worried - No. In fact, I thought that image looked pretty clean. Just me, or just my monitor at work? IDK - I really didn't see anything that looked out of the ordinary.

I honestly don't see anything wrong with the image, even for an ISO 400 image. I don't think there is an excessive ammount of noise.

[aparmley]

Well guys thanks everybody.

aparmley - special thanks for mentioning monitor. This I guess was a keyword :)

I looked at the 19-in CRT at home 17-in CRT at work and images are clean, no trace of the noise on 19-inch and on hight magnification it looks like fine (e.g. yes may be not focused somewhere but this is what I expected- not noise )

So thanks again everybody and ... don't buy cheap LCD monitors :) Mine is going back to the shop!

Glad I could help. ? ? So your images were looking crappy on your LCD? But look good to you on a CRT?

My images always look a lot better on my CRT at home than they do on my laptop. . . just one of those things.

[Hobbit]

Yes my LCD I guess was a part of the problem. But when I told this to one of my friends he said that he recently bought LCD 24 in and images look especially amazing on that 1. Didn't have a look at it yet. So I guess also depends in LCD - how much you invest.

[aparmley]

So I guess also depends in LCD - how much you invest. Another area in which "You get what you pay for." I hear those 24" Dells are quite nice.

[cdifoto]

I have a cheap Princeton Tech LCD, albeit quite small at 15" that I have no problems with...


Of course there are better LCDs but I don't consider this one crap.