Is your Digital Noise Blaring - photography gremlins

Submitted: Saturday, Mar 24, 2007 at 18:46
ThreadID: 43595 Views:2516 Replies:8 FollowUps:11
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Matt asked this question on another thread, so to keep it OT, I will post a few thoughts here.

With film cameras, when we wanted to make photographs in low light, we used "fast film" or ISO 800 (say) film. The ISO is a standard measurement for sensitivity to light - the higher the number, the more sensitive, so film that needs less light (and thus allows one to use "faster" shutter speeds) for desirable exposures has a higher ISO reading.

Similarly, with digital cameras, the sensors are the equivalent of the film, and they are made to be optimally sensitive to a certain amount of light that is similar to the amount of light required for desirable exposures on traditional ISO 100 or ISO 200 films. Most of these sensors will work with less light, and either with Auto settings or by manually changing the ISO settings of the camera, one can reduce the amount of light required for desirable exposures, and thus speed up the shutter speeds.

Even with ISO 100 film, however, the film emulsion - the chemistry that was activated by exposure to light, is made of very fine particles. The higher the ISO, the larger the particles. If you make large prints from even an ISO 100 film, a close inspection reveals the grain. Even with small prints from an ISO 1600 film, the grain is very evident.

So it is with the digital equivalent. The sensor is a computer chip that converts light energy into electronic signals. Just like in radio systems, for instance, these signals are prone to noise - interference if you like. This interference can come from other energy sources (IR light and heat, other electronic signals in the vicinity - the other components on the miniaturised camera - the memory card, the zoom and focus motors, etcetera to name a few). Thus you have a signal to noise ratio that describes how similar in intensity these two energy sources are. At their designed optimum light sensitivity (taking photos in normal sunlight conditions) the ratio is extremely high. At very high sensitivies, the amount of energy from the light readings is getting to be much lower and thus the noise energy is starting to get very similar to the signal energy, so we start to notice the noise - if it were a radio signal we would hear the buzz. In the digital image we see strange colours and discontinuities in the tones in the image.

Most of us have seen it, I am sure, if we have spent any time looking at our own or other people amateur photography.

Here are some things that affect noise:

1. how dark the image is - noise is worst in shadows, because surprise surprise the energy levels in the dark are lower
2. how small the camera is - the smaller and closer the components, the more prone to one component affecting another, thus increasing the noise (thus digital SLR cameras will generally have much less noisy images in sub-optimal light conditions than compact cameras)
3. when images are extremely overexposed - a really bright area in the image creates huge energy flows in parts of the sensor affecting the parts of the sensor that had low energy flows
4. how much image compression the camera software or settings make - image compression results in loss of image quality adding noise to the image, as does image editing and adjustments, unless you have professional tools and skills
5. the amount of effort, development and technology that has gone into the design of the camera
6. chromatic aberation is another noise effect from the optics - the smaller the optics (the lens), and the less sophisticated it's design, the higher the purple or red fringing in areas of high contrast.

So, that is what noise is and why it is caused. But why do you care?

Well, if you take photos - particularly those in low light situations, your photos may not look as lovely (eg. that beautiful sunset) as you had hoped for - you will see bountiful noise in those sunset and weather shots shown with the TV news.

If you are only going to display them on your PC at low resolution, this may not bother you. If you expect to publish them, print them, or sell them, then this could be a show-stopper.

Sites like and others review cameras (not all of them because there are 1,000s of them released each year), and noise will be one of those things that they assess. Taking some photos with the camera you are thinking of buying in low light conditions and taking them home and looking at them in detail on your PC is a way of determining if the levels of noise are acceptable.

Digital cameras allow us much more flexibility in working in low light conditions - we don't have the change films. As a consequence, we have to worry about noise.

Here is a DP Review article on the subject with some images, for those that wish to read more.

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Reply By: Keith_A (Qld) - Saturday, Mar 24, 2007 at 19:26

Saturday, Mar 24, 2007 at 19:26
Thank you for that reminder Andrew. As with any tool that gets infrequent use, I forget some of the simple things - like changing the ISO in low light.
Next time one of my night pics turns out badly, it might even jog some of my neurons into remembering this post.

Your explanation was both thorough and clear.......appreciated.......Keith.
AnswerID: 229492

Follow Up By: Andrew from Vivid Adventures - Saturday, Mar 24, 2007 at 19:36

Saturday, Mar 24, 2007 at 19:36
Interesting point Keith - give that camera more frequent use for a while and you'll make it second nature.

As with any tool, if you get familiar with it you don't have to think about it and using the tool doesn't get in the way of the task and allows the tool to work it's best.

People's photography would improve in leaps and bounds if they just learnt on thing at a time by doing it multiple times. For example, the next time you're taking photos take one of the following skills and repeat it 7x and it might become a habit:

1. stable camera hold and stance, and caressing that shutter button like it was a woman's ...
2. what really was the camera focusing on (the red or green squares that most cameras have to tell you what you are focused on)
3. half-press focus and reframe for more interesting compositions
4. reviewing an image for sharpness
5. reviewing an image for correct exposure, and using exposure compensation if necessary
6. assessing whether a flash would help or hinder
7. trying other angles - getting higher, getting lower, going for the angles ...

FollowupID: 490260

Follow Up By: Mike Harding - Sunday, Mar 25, 2007 at 06:54

Sunday, Mar 25, 2007 at 06:54
I doubt I'll ever be able to press the shutter release again without being distracted by other thoughts :)

Good post Andrew. One other point worth mentioning is that some (all?) digital cameras will automatically change the ISO speed in low light conditions. I turn this feature off and normally keep mine locked to ISO100 or so.

Mike Harding
FollowupID: 490316

Follow Up By: Andrew from Vivid Adventures - Sunday, Mar 25, 2007 at 07:31

Sunday, Mar 25, 2007 at 07:31
Good observation Mike.

A lot of cameras have "Auto" ISO setting ... this sounds great, and indeed may be very good, but it is rather arbitrary about when it decides that you need to use a higher ISO (generally you can't set the criteria).

As a result you don't know when your shots are going to be noisy, and some cameras don't even put the ISO actually used in the EXIF data stored with the photo (I guess that is a subject for another day) so there is no way of looking at what was used.

If the noise is not going to bother you, and being able to take photos without thinking in any conditions is what you need, then the Auto function is for you. Otherwise, pay attention to the camera's shutter speed selected and if it is getting less than 1/100s for wide angle lenses and 1/200s or 1/300s for telephoto end of the zoom, then changing the ISO can help if you can live with the noise - otherwise, get a tripod.

Interestingly the cameras with Auto ISO tend to have the higher levels of noise at higher ISOs too ... the Nikon D-SLRs are an exception.

FollowupID: 490319

Reply By: Aknot - Saturday, Mar 24, 2007 at 19:49

Saturday, Mar 24, 2007 at 19:49

Appreciated the effort put into that reply to earlier question, was very interesting and I even understood most of what you said. THANK YOU enjoyed reading a very informative thread as was previous thread earlier.

AnswerID: 229498

Reply By: Dave198 - Sunday, Mar 25, 2007 at 03:37

Sunday, Mar 25, 2007 at 03:37
Thanks for the very informative post Andrew. Not.

Now you will have me bringing up all my photos on the screen analysing every shot.
This is going to cost me lots of time.

Don't post another one like that for a while so I can get some serious study done after I look at the mistakes in my photography.

Dave :>))
AnswerID: 229537

Reply By: Richard W (NSW) - Sunday, Mar 25, 2007 at 07:02

Sunday, Mar 25, 2007 at 07:02
Excellent summary. I can never be reminded enough about this stuff.
Noise Ninja in PS2 helps a bit. ;)
AnswerID: 229544

Follow Up By: Andrew from Vivid Adventures - Sunday, Mar 25, 2007 at 07:39

Sunday, Mar 25, 2007 at 07:39
That is also a good point Richard.

For the uninitiated Richard is not talking about some Playstation Game of Photography.

There is a range of software available for "Noise Reduction" - some cameras even have noise reduction in the camera. Most of this software works with Photoshop CS2 (I think this is what he was refering to), or PaintShopPro. He mentioned NoiseNinja which, like Richard, I have found to be the best, but it is rather technical to use. There are quite a few others - notabley NeatImage, and DxO Optics.

There is Noise Reduction built into the Adobe Photoshop Lightroom recently released which might help Dave with the task of reviewing his photography - it certainly is an efficient way of working with large numbers of images.

There are drawbacks - the sideeffect of noise removal is the loss of detail in the image, so while it may smooth out those skin tones, and make the image more pleasant too look at, you will no longer see the eye-lashes on the tiger that Willem was staring down that late evening in the game park so many years ago - oh yeah, that was film. Oh, I forgot to say, the same software works equally as well for grain removal, so that the grain of a slide or negative isn't so noticeable.

FollowupID: 490320

Reply By: Member - Brian H (QLD) - Sunday, Mar 25, 2007 at 08:16

Sunday, Mar 25, 2007 at 08:16
I have been playing with my camera and many a time I will set it up with a tripod and put on manual and just mess with the settings and see what happens. This is done in varying lighting. At least my camera I can see what I used to take the photo etc, which helps for next time.

It is a big learning curve for me I like looking a peoples photos but just for interest sake I would like to know the camera / len settings they have used to get some of the shots. My pet hate would have to be taking the time to get your photos and when you return home they are cra$ for what ever reason. One of my reason for wanting a laptop on my travels, check before I leave.

Your info above helps and thanks for your time in putting up.

Of course with the vision you have given of the shutter button ...... lordy lordy taking photo's has a whole new outlook and hmmmmmmmm feel :) :)

Come to think of It may just go take a photo :) :)


AnswerID: 229551

Reply By: TroopyTracker - Sunday, Mar 25, 2007 at 18:15

Sunday, Mar 25, 2007 at 18:15
Thanks Andrew,

Now I know! Currently looking around the net for reviews of the cameras I'm thinking of.

Thanks again,
AnswerID: 229632

Follow Up By: Andrew from Vivid Adventures - Sunday, Mar 25, 2007 at 18:20

Sunday, Mar 25, 2007 at 18:20
You might like to use the checklist:

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Follow Up By: TroopyTracker - Sunday, Mar 25, 2007 at 18:42

Sunday, Mar 25, 2007 at 18:42
Will do, thankyou,

FollowupID: 490439

Follow Up By: Andrew from Vivid Adventures - Tuesday, Mar 27, 2007 at 08:09

Tuesday, Mar 27, 2007 at 08:09
Hi Matt,

If you were the person looking at the Olympus SP550UZ, there is a detailed review of it now on DP Review here:

FollowupID: 490748

Reply By: Member - Craig D (SA) - Tuesday, Mar 27, 2007 at 08:35

Tuesday, Mar 27, 2007 at 08:35
M6 + Summi and K25 - what noise? Said tongue in cheek of course :))))))))))))
AnswerID: 229963

Follow Up By: Andrew from Vivid Adventures - Tuesday, Mar 27, 2007 at 09:39

Tuesday, Mar 27, 2007 at 09:39
talk about accessible ... ;-)

can you still buy K25? what is the resolving power of K25?

Andrew who prefers Velvia 50.
FollowupID: 490766

Follow Up By: Member - Craig D (SA) - Tuesday, Mar 27, 2007 at 10:27

Tuesday, Mar 27, 2007 at 10:27
Hi Andrew, I still have stock of K25 and K64 in my fridge:)

The resolving power of K25 is 63 at 1.6:1 and 100 at 1000:1
Velvia 50 is <80 at 1.6:1 and 160 at 1000:1 for comparison.

These films are gorgeous when using Summicrons and sharp as chit when I switch to Canon L-series lenses. The Summis, as you would know, just glow. Ever seen B&W landscapes shot with Leica glass? Ansel would be jealous:)

FollowupID: 490774

Follow Up By: Andrew from Vivid Adventures - Tuesday, Mar 27, 2007 at 11:19

Tuesday, Mar 27, 2007 at 11:19
Yes - jealous or broke ;-)

I have plans for Summis on my 5D ...
FollowupID: 490786

Follow Up By: Member - Craig D (SA) - Tuesday, Mar 27, 2007 at 12:18

Tuesday, Mar 27, 2007 at 12:18
Ur obviously a full-frame fiend :) Might trade my 1V HS in one day (not!), nor would I part with any of the L's. Might let the Bronica ETRsi go though and get a Mamiya II if I ever get the bug again (I was a wedding photographer (own studio) and a photojournalist and got a little burnt out - now I rarely even press a shutter believe it or not).

FollowupID: 490797

Reply By: TroopyTracker - Tuesday, Mar 27, 2007 at 17:49

Tuesday, Mar 27, 2007 at 17:49
Thanks for the link Andrew,
Great site,
AnswerID: 230068

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