2

Just curious if anyone can help with this?

I am using a Canon 5D Mark II and it seams to be having noise issues at ISO 250 and up and especially at ISO 400? What is going on?

In low light when my flash doesn't hit the subject very well it seems to be very extra grainy and also a bit blurry. Even when I am not in low light such as outside during the day and still using flash at say ISO 400 I still see noise? Once I am home and zoom in a bit it is so ridiculously grainy and not clear.

Any ideas about what may be causing this?

Joanne C
  • 33,138
  • 4
  • 72
  • 132
kristen
  • 29
  • 1
  • 2

2 Answers2

5

It sounds like you are underexposing. Noise is generally a more significant problem when the brightest pixels in your image are only about 18% gray level. If this is the case on a consistent basis, especially if you are encountering blurring (I assume due to camera shake) then you are plain and simply using too low of an ISO setting.

If you use a low ISO setting and under-expose, then boost that exposure in post, your actually amplifying the effects of noise a lot more than if you use a higher ISO setting. If you are getting blurry, noisy shots at ISO 400, try ISO 800 or even ISO 1600. The goal is to saturate your exposures, pushing the average per-pixel luminance beyond that 18% gray level. The more pixels you can saturate beyond an 18% gray level, the less noisy your image will appear. If you over-expose but do not blow out your highlights, you can recover exposure in post with a little negative exposure compensation or highlight recovery.

The fear of using a "high" ISO setting is often the cause of noisy photos. High ISO is not bad, and in low-light situations (even with flash), you need to use the highest ISO setting you must as dictated by minimum shutter speed requirements. In general, the camera will do a better job of boosting exposure while minimizing noise when using higher ISO settings than you could generally do by shooting at a lower ISO setting and trying to compensate for underexposure in post.

jrista
  • 70,728
  • 15
  • 163
  • 313
1

There are many factors to "noisy" images. So listing them for your consideration

  1. Focus. Surfaces that are even slightly out of focus will appear more grainy than the parts that are in sharp focus.
  2. Brightness. The darker the area, the more noise there are. Just because you are using low ISO doesn't mean there are less noise. A dark area in low ISO will be approximately as noisy (or maybe a bit less) as a bright area in high ISO.
  3. Lighting. Certain lighting condition introduce noise more than others.

Of course without image, it's hard to say. The list is probably by no means comprehensive as well. But just because you are using low-ish ISO doesn't guarantee your image will be noise free.

Elaboration due to popular demand :D.

  1. Focus. It's pretty simple maths. Imagine you have a concentrated source of light such as a candle light in pitch dark. If it's in focus, all the light will be directed into a small single area on the sensor. If it's not in focus, it will be blurry and spread acorss a wider area. Less light = more noise.

  2. <--->

  3. Lighting. There are 3 color channels the camera can understand. RGB. On the photo sensor there are usually 2 photo sensor sites of one channel and 1 for the other 2 channels. So RRGB or RGGB or RGBB in a 2x2 grid. The channel with more photo sites would produce less noise. This one differs from camera model to model (Or not, I just know the theory behind it).

    Canon 7D for example have horrendous blue channel. (Personal experience)

Sleeper Smith
  • 191
  • 4
  • I do not agree with point no. 1. I have never seen such a problem but opposite. Also, can you please elaborate point no. 3. Which lighting induces more grain than other? – Nitin Kumar Jul 30 '12 at 10:07
  • I am sure all these need to prefixed with "at high ISO", because at typical ISOs none of these situations will produce any discernable noise. – Burhan Khalid Aug 04 '12 at 20:06
  • I do not agree with point no. 2. A darker image will have a higher signal to noise ratio than the camera is capable of, but there will not be more noise in the dark areas than the light areas. – Phil Sep 21 '12 at 04:14
  • 1
    Haven't heard of any RRGB or RGBB sensors, they all tend to be RGGB (because human eye is most sensitive to green). – Imre Nov 29 '12 at 07:06
  • 1
    @NitinKumar: Actually, noise DOES show up better on OOF backgrounds, assuming the background is not high key. In complex subject detail, noise gets drowned out by useful detail. However in a smooth background that has little fine detail and large areas of flat color or gradients, the effects of noise are more prevalent. So, I agree with point #1. I also agree with point #2, noise IS worse in the shadows, because S/N is LOWER in the shadows, not higher. Not sure about point #3...LESS lighting could result in lower exposure, resulting in lower S/N and more noise. – jrista Dec 04 '12 at 22:33