Keep the Noise Down
If you are interested to know how to keep noise levels down in your images then please read on. Here are a few thoughts from my own experience that have helped me. Noise, most importantly, means loss of image detail, so low noise is important if your desire is to produce clean, clear, quality images.
I won’t go into the finer details and technical jarg regarding digital noise here, I am not a scientist, camera designer or technician – I just take photos! Alrightey then …
Firstly, I shoot mostly in Manual or Aperture Priority modes preferring more control over the camera settings and performance
- Keep your ISO setting low. Higher ISO means higher noise levels, so for all but sports and action, I keep my camera ISO setting at minimum. This often requires the use of a tripod or monopod to keep the camera steady, but I am serious about image quality so I consider this well worth the effort. There is much talk about the hi ISO abilities of cameras like the Nikon D3s and many statements regarding the image quality. If you are serious about fine art prints, landscape, product photography, food photography etc then even with a very highest quality sensor, lower ISO will always give cleaner, superior results and professional quality large prints – by large, try 630mm + high x 2300mm long, Durst Lambda printed on Kodak Professional Endura print paper, view the image here.
- Long exposures introduce noise, so keep your exposures times as low as practicable. This is not always possible in which case I set my camera long exposure noise level reduction. Generally I have found with the cameras I currently use, exposures under 15 seconds are all pretty low noise if I have exposed the image correctly. Exposure times over that, is where the cameras long exposure noise reduction setting helps.
- Under exposure will also add noise to images when trying to increase the exposure level in Photoshop or Lightroom (or which ever is your software of choice). I expose to the right, meaning the bias of my exposure is to the right of centre on my camera histogram.
- After each exposure or set of exposures I always check the histogram to ensure correct exposure – that there is no “clipping” the graph on either the left or right sides of the histogram. In practice a small amount of clipping can be brought back in Lightrooom but too much and you have lost information from your image, meaning there will be either total black or white areas where there is no image detail recorded.
Exposing to the right is not over exposing but keeping the exposure on the + side or right side of centre on your histogram. If I adjust an image exposure up by any considerable amount in Lightroom 3 or Adobe Camera Raw, I have found noise introduced and less definition resulting, whereas adjusting the exposure down on a brighter image (the image of course is not overexposed, only brighter than I want the final image to be) retains detail and has not introduced noise.
- A hot camera sensor will cause more noise, some suggest the noise level doubles for every 5 degree Celsius increase in temperature. Basically I keep my camera in the coolest spot possible, shade – but not sitting in the car at 45+ degrees C as it can be in parts of Australia. Nikon recommends operating in temperatures up to 40 degrees C is ok, which I have found it to be in practice also. Remembering of course that ambient temperature is considerably increased inside a black camera body exposed to direct sunlight.
- A larger sensor area will produce lower noise levels, this is why full frame or FX sensor cameras (35mm film equivalent) produce cleaner images than cropped sensor cameras, four-thirds micro and compact point-and-shoot cameras. Medium format cameras generally produce cleaner images again. This has something to do with pixel pitch and the amount of gap around each pixel or photodiode on the sensor plate, a larger sensor plate having more space around each individual pixel. It follows that smaller sensors with the same megapixels has them all closer together.
- Shoot in camera RAW if possible. Some of the smaller cameras will not do this but most DSLRs have a camera RAW setting which I use exclusively. Jpegs, even at the highest quality setting strip information from the image. Camera RAW files – NEF for Nikon, Canon CR2, Fuji RAF etc, these files are just the raw data the camera has recorded for the image, they are not useable in this state and must be processed and converted into a usable format, the most common being JPEG and TIFF. Camera RAW files record the most information to bring the best out of your image, but remember the basic premise of any processing is GIGO, or Garbage In Garbage Out. There is nothing that can correct a really crappy image. I check my lens is clean, focus, exposure (meter in the view finder and the camera histogram after the shot) framing, white balance … and push the remote button!
- I am not a software expert and have not used alot of RAW converters, Nikons’ NX2, Adobe’s Camera Raw and now Adobe’s Lightroom 3 which has the latest Adobe Camera Raw technology built in. I use Lightroom 3 almost exclusively, simply the results have won me. There is other software available, but that is another post – sorry!
- Post processing. I have used Nikon ViewNX, Nikon (Nik Software’s) Capture NX2, Adobe Photoshop Elements, Photoshop CS5, Adobe Camera Raw, Lightroom 3 and Noiseware Professional. Of these I have found Capture NX2, Noiseware Professional as a plugin to Photoshop CS5 and Lightroom 3 (which is Adobe Camera Raw built in) all very good. Of course excessive noise is just that and a reject image for me.
- If you don’t process your images after downloading them, consider learning to do so and making this your practice. Nothing too complicated about basic processing but the results will bring a smile to your dial if you love photography. In camera processing is another option but once again – that is a yarn for another post!
I am sure there is more that could be covered, but by following some basics and making them my standard practice, my images quality has improved and that is what we are all about really.