Noise is a killer

Anybody know what the picture above is of? I'm not sure I could guess if I didn't know already. It's someone's eye. In fact, it's the eye of a musician who goes by the name Shura, but you can't really tell it's an eye at all. There's a lot of smearing which means that detail is lost; there is lots of speckling, particularly in the shadowy areas; and although it's not too bad here, there is sometimes a lack of contrast because regions of low contrast are wiped out by the noise, which tends to be quite contrasty.

Noise is caused by the electronics of the camera (or the scanner, if you're scanning film. N.B. noise is not to be confused with film grain). A large percentage of noise comes from the sensor in your camera, and in general, the larger the sensor, the less noise in the images. This isn't the whole cause, since there's also an effect that comes from the closeness of the light-sensitive photosites on the sensor itself. In general, the large, expensive cameras will have a large sensor (often called a full-frame sensor, because it's almost the size of a frame of 35mm film). Prosumer level cameras have an APS-C size sensor, which is considerably smaller (1.5--1.7x smaller) than full frame. Most compact cameras and MSCs/CSCs (like the new Olympus Pen series) have sub-APS-C-sized sensors, and thus suffer from larger degrees of noise. Some of this noise will be cleaned up by the camera's software when it processes the image that you've taken, but some remains, especially when you have the camera set at a high ISO, that is, the sensitivity of the sensor is pumped to higher levels.

In this picture, the problem is lack of light. I'm in a dark room, I'm quite far from the stage, and the little tiny photons reflected off Shura's face aren't finding their way into the end of my lens. Here I'm shooting at 90mm on my zoom lens, with an aperture of f/4.5, a shutter speed of 1/40s, and my ISO is bumped all the way up to 6400, which is pretty much the useable limit on my camera. In fact, I'm probably shooting beyond the limits of my camera here. As a rule of thumb, your shutter speed should be faster than one over the focal length you're shooting at. So because I'm at 90mm here, I should be shooting at 1/100s to eliminate any camera shake that occurs when I take the picture. If I was to shoot at 1/100s, the picture would be underexposed because there wouldn't be enough time on the exposure to collect all the necessary photons. I could open up my aperture to make it wider (e.g., f/2.8, see diagram below), but for this lens, f/4.5 is my limit. Luckily on this lens I have vibration reduction, a system which tries to compensate for camera shake. This can often give you a 3-4 stops of light bonus, so that even though I'm shooting at 1/40s it can seem like I'm shooting at 1/320s in terms of camera shake. And this image in general is quite sharp, so I'm happy.

Is there anything that can be done about the noise in the top image? There is a little bit of rescuing that can help the situation. It depends on your post-production software (Photoshop, Lightroom, GIMP, etc.), and how adept you are at tweaking the settings, how successful this is. Personally, I'm pretty useless at this. I use a stand-alone piece of software which is called Neat Image. You select a region in the photo where there's no drastic colour change, and it analyses that region and removes the noise from the whole photo depending on what it finds. It has mixed results, depending on the quality of the region you've selected, see below.

As you can see, it's done a pretty good job of removing the speckles (luminance noise) and the random blobs of blue/green/yellow/red (chroma noise). The payoff is that the image is now a lot more soft than it was before, which means that we need to sharpen the image carefully, and potentially more than we normally would for a noiseless image. But when it comes down to either taking a noisy image or taking no image at all, it's probably best to take it, and do the best you can with the noise post-production:

The difference can be seen particularly in Shura's face, the shadow areas (compare the noise top-left to bottom-right), and any areas of solid colour, for instance in the red curtain. Differences may appear be minimal on this scale (800 pixels), but when blown up they make a clear distinction between an ugly photo and a not-so-ugly one.

Lack of focus

So, the photo above isn't entirely what I mean by lack of focus, but it is an amusing example of getting the focus wrong. Here we see the lovely Emma and Becca from the band Peggy Sue sharing a moment whilst playing. It would have been a fairly nice shot if I could have placed the focus sharply on their faces, whilst throwing the crowd a little bit out of focus to give some separation in the shot. I was shooting fairly wide, at f/4.2 and a focal length of 86mm. An f/2.8 would have given me a really nice separation, but unfortunately I don't have the cash to splash on a 70-200mm f/2.8. The issue with this photograph, then, is wrong focus. I missed the focus on the young women sharing a musical moment, and instead managed to get a picture of a fierce-looking heavy-built man appearing like he's going to scale that barrier and give me a punch on the nose for taking his photo. The reason was that I just wasn't paying attention to my focus points. I had just been taking a photo of the lead singer in the band (her guitar is in the lower right corner) and swung around to see Becca and Emma getting into their groove, and I pressed the shutter release. Oops. I realised at the time that I'd missed the focus, changed the focus point to rest on the closest of the girls*, and snapped again... but by then the moment had passed. A missed photo opportunity. Dangit.

This is more what I'm talking about when I say "lack of focus". What we have here is a fairly reasonable picture of a famous landmark (Canary Wharf in London). It's quite dynamic, due to the radial streaks in the sky. It's quite cold in tone, which echoes the glass and chrome of the buildings, and the water. It's reasonably sharp, too. However, there's no focus to the photograph. There's nowhere for the eye to rest. What should be the focus, the main Canary Wharf tower in the centre, is too small in the frame to have an impact. It is helped slightly by the leading lines of the buildings around it focusing in on the main structure, but there's too much void -- the empty sky, the empty water -- when the building should be dominating.

The moral of this story is, then, to have a strong focal point to your photograph. Often, when you have a wideangle shot like this one, there should be some foreground interest. When you're photographing a building with a wideangle lens, however, it may be better to get in very close to it, making the most of the dramatic converging vertical lines that you'll get in that situation, and making your building fill the frame. When you don't have a wideangle shot, it can be better to place your focus on a line of intersection of thirds -- divide your shot up vertically and horizontally into three equal parts, and where the lines cross towards the four corners of your photograph, these are the "sweet spots" where your subject can sit quite comfortably. This is known as the "rule of thirds", although it should only ever be used as a guide, not as a hard-and-fast rule!

* Just a little tip: I would focus on the closer of the girls because the "region of good focus", let's say, extends more behind the focus point than it does before. As a rule of thumb, when you have your subjects at a range of distances, you should focus about 1/3 of the way into the frame. So I would focus on Emma, the girl on the right, who is slightly in front of Becca, so as to get them both into the region of good focus. If I was to focus on Becca, because the region of good focus extends less towards me, there would be a higher chance then that Emma would be out of focus. I hope that makes sense!

Introduction to Photo Phrustrations

I am a photographer. I'm not a professional, probably somewhat through lack of talent, but mostly through choice ... I don't think I'd enjoy it. Photographers are often poorly paid, and poorly respected: I like to be both well paid and well respected! However, I take a lot of photographs, and people have asked me to do "professional" jobs before -- photograph music festivals, photograph school visits, photograph weddings -- so I have some experience of photography.

Photography is continually very frustrating to me, though. There's probably not a day that goes by when I'm taking photos when I'm not thinking "Arggg, I wish I could have done that better. I wish this picture was better exposed. I wish this picture was sharper. If only I'd crouched down lower. If only I'd given the subject more space in the photo. If only I'd brought my tripod." I'm frustrated with myself, with my equipment, with the weather, with missed opportunities, with lack of post-processing skills. And I guess plenty of you are too. So perhaps we can pool our knowledge so that by sharing tips and tricks, or even just our moans, we can get more enjoyment out of our photography by discussing it.