Not Your Everyday Banana

by Bart Arondson

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I'm using a Canon T2i and I was sitting in the audience taking some photos for my friends. (I'm not the wedding photographer).

I took this shot with the 50mm f/1.8 at 1.8 and at 100 ISO. No flash, Spot metered on the brides face.
I take all of my photos 2/3 steps underexposed, so after putting this in Lightroom, I noticed a lot of grain. Is this grain normal for the T2i and will a better sensor yield better results?

Before Editing: enter image description here

After Editing: enter image description here

Full Image http://i.imgur.com/RXrqsPd.jpg

Is this normal for a T2i. I know I'm extremely zoomed in and everything will have grain in it no matter the camera, but will this be better on a better camera? or will the sensor pick up and fake the same amount of grain?

Here's another full sized pic that you can very noticeably see the grain in the image. http://i.imgur.com/hYwiO04.jpg This picture was taken on a 30 second exposure. I turned up the vibrance a bit and even upped the luminosity to get rid of some of the grain, but even not zoomed in, you can see it.

I just always notice real photographer's pictures seem to turn out much more clear. Any tips?

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Well, the 2/3 stop underexposure doesn't help. Usually if digital photographers adjust their exposure it's 'to the right', or overexpose to maximize information and minimize noise (grain). The second concern is that you haven't told us the ISO equivalent that your camera was set at. If you shot at a high ISO then your images are more likely to have noise. –  BobT Oct 7 '13 at 18:03
    
Oh yes! That is very key. I was shooting at 100 ISO. Here's the Information from Lightroom: i.imgur.com/Cx3oLnI.png. Hmm, I always thought I should shoot under exposed to get more detail from the places that I would later like to overexpose - like faces –  ntgCleaner Oct 7 '13 at 18:30
    
Noise is about the amount of light hitting the sensor, not ISO, I've added two examples to my answer, my 550D (T2i), "crappy" kit-quality lens, ISO 400 with no noise –  Nir Oct 7 '13 at 19:56
    
Blue component is a lot noisier/grainier than red and green. A greyish subject might have a lot of blue innit, making it show noise when underexposure is corrected in post. –  Esa Paulasto Oct 12 '13 at 13:25
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4 Answers 4

up vote 3 down vote accepted

Noise is caused by not having enough light hit the sensor.

The oversimplified but easy to understand explanation is that your camera has a constant level of noise "brightness" is every image, when the picture is very bright the real detail overpower the noise and you can't see it but when the picture is dark the noise and details are at a similar level and the noise is visible.

If you increase the brightness of the picture (either in post processing or increase the ISO) you are increasing both the details and the noise by the same amount - so the more you increase brightness in post the more noise you will get.

So what can you do?

  1. Don't under expose, brighter original image equals less noise

  2. If you need more light higher ISO causes less noise than increasing exposure in post (I have the T2i and you can get noiseless pictures at ISO 400 and even 800 if you have enough light)

  3. You can reduce noise even more by overexposing a little bit (without clipping the highlights) and reducing exposure in post, this is called "expose to the right" (ETTR), but this reduces the image quality in other ways (there are always tradeoffs) I personally don't do this [update: I may be wrong about it reducing image quality, can't find details about it right now].

Update: Here are some examples, 550D/T2i, "low quality" lens, strait out of camera JPEG, practically no noise

  1. Manual mode, ISO 400, 1/200, f/6.3, indoor with bounce flash, EF-18-135 IS (kit lens!!!), JPEG strait out of camera (I shoot RAW+JPEG), full image followed by 100% crop (you can see in the 100% crop I slightly missed focus, really annoying):

enter image description here enter image description here

  1. AV mode with +1 exposure compensation, outdoor in direct sunlight, f/8, 1/800, again ISO 400, again with the 18-135 and again JPEG strait out of camera

enter image description here enter image description here

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Just curious, what drawbacks does ETTR have? If you're not clipping the highlights, most, if not all the information should still be there in the RAW... –  Chinmay Kanchi Oct 7 '13 at 19:13
    
@ChinmayKanchi - I'm not sure, I don't remember exactly and can't find the original source, I think it was something about color accuracy or saturation. I personally don't care much about ETTR because I don't like to spend time editing so I didn't really care about the details at the time. –  Nir Oct 7 '13 at 19:49
    
@Nir Great and detailed answer! I am going to go home and play around with the settings again. Thank you for the examples as well, There's practically no noise! Thank you again! –  ntgCleaner Oct 7 '13 at 23:04
    
The biggest disadvantage of ETTR in low light is the loner Tv that might mean motion blur caused by camera or subject movement. Sometime you have to underexpose slightly to control the motion and then live with the noise. And there are some excellent tools for dealing with noise in RAW files before converting them to jpeg. –  Michael Clark Oct 8 '13 at 2:02
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The other problem with ETTR is that it's easy to blow the highlights, which often looks worse than a little noise. –  mattdm Oct 8 '13 at 10:35
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Most of the noise appears to be a result of the underexposure. Did you shoot RAW or JPEG? The underexposure hurts in the dark parts because it is falling outside the dynamic range of your sensor and if you aren't shooting RAW that will be greatly compounded. Some underexposure is nice for highlight prevention, but if you go too far, you are going to sacrifice a lot in the shadows, particularly with a camera with a relatively small (comparatively) dynamic range.

A lot of the distortion looks like aberrations from the lens as opposed to noise too. (I mainly only see noise in the dark parts that got too underexposed and were boosted too far back up.) Better optics are generally the reason that professional images look so much better. Photos on my old xTi look far better when I slap on my 24-70 f/2.8 II. Sure they look better on the 5D Mark iii, but the optics make a huge difference.

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Thank you for this answer! I am shooting in RAW and even though it's their cheapest lens, I thought the Canon 50mm 1.8 was great glass? I will turn the exposure up a bit and experiment some more. I am currently saving up for that exact 24-70 f/2.8 II lens right now. –  ntgCleaner Oct 7 '13 at 19:03
    
If you're shooting RAW, try overexposing by about 2/3-1 stop. Basically as much as you can without blowing out the highlights. Then drop the exposure in post. You'll be stunned at how much this helps. My aging 30D feels like a brand new camera since I started doing this! –  Chinmay Kanchi Oct 7 '13 at 19:08
    
There is nothing at all wrong with the 50 f/1.8, but it will be quite a bit sharper up around f/2.8 than it is wide open. But that is not the source of the grain -- the grain is as others have mentioned likely due to the underexposure. –  Patrick Hurley Oct 7 '13 at 19:24
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@ntgCleaner - it isn't that it isn't a solid lens. For the price, it's great, but it's also not high end glass. My 24-70 f/2.8 is slightly sharper than the 1.8 and I'm pretty sure even the 1.4 from what I can recall. Keep in mind, we're also pixel peeping quite closely to see any issues. It's still a great lens, just not top quality. –  AJ Henderson Oct 7 '13 at 19:30
    
@ChinmayKanchi - I don't know how it is on the T2i, but I know on my 5D Mark iii, I can't over-expose without blowing highlights. I think some of the more recent cameras have moved towards putting more emphasis on getting as much detail out of the shadow as possible. That said, a 2/3 underexposure is still quite a lot. If I do under-expose, I do it by 1/3 at most, and that's with a high dynamic range sensor. –  AJ Henderson Oct 7 '13 at 19:32
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Did you shoot raw? If you did, then you have greater control over both colour and luminance noise reduction as well as sharpening. It looks as if you've lifted the exposure on a JPEG which doesn't have quite the same latitude (technically 64x less for 14-bit raw) for modification as a raw file does.

With my raw files in Lightroom I personally use 20 on luma, 25 on colour and 40 sharpening with 1.2 radius. I used to use a Canon 60D but now I shoot with a 5D Mark III.

Underexposing is not ideal in most cases unless there is a significant reason for you to restore highlights and maximise dynamic range, such as landscapes. Wedding photos often benefit from a "bright, sunny disposition", and using normal or slightly brighter exposure (say +0.3EV) can produce nice results, both technically and visually.

I've tried both underexposing and overexposing but now I don't do either. I simply shoot the correct exposure and adjust in post. ETTR is not really possible in high dynamic range scenes anyway. The only time I ignore the meter in the camera is when it is off and the subject is too dark or bright due to some other factor in the scene.

Unlike raw-capable digital cinema cameras, I know Canon DSLRs do not show us the raw histogram but rather the histogram based on the tone curved, final JPEG, which makes it hard to guess when highlights are really clipping. With a raw histogram, you know exactly where the exposure lies on the sensor.

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Looks like you original image taken was heavily as under exposured. Bumping up shadows showed not only grain also vertical banding which is typical for many Canon sensors.

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This may be true but in general on this sit we like to see claims about defects being typical for a brand backed up by references. Thanks! –  mattdm Oct 12 '13 at 13:46
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