ISO800

Shooting ISO 800 on the Dimage 7

This is version 2 of thise article April 16, 2002.

Introduction:

 Well, everyone has tried it, and the universal consensus is that ISO 800 is too noisy for everyday use. Here I'll present some tips for using ISO 800 that will help improve your results considerably vs. the default settings; you may be surprised at how well this works if you use a combination of all four of these tips. Each tip will improve your ISO 800 shots a little bit. Using all four is a dramatic improvement. Yes, you can also use software packages to reduce the noise later also.

 

Tip #1 Use soft sharpening

Theory:  ISO 800 is noisy. Very Noisy. Unfortunately, the sharpening routine in the camera sees the random noise and "thinks" that it is fine detail... and tries to sharpen it. Sharpening in a digital camera works by accentuating any changes along boundaries. Say for example that you have a dark table edge against a light background... sharpening will make some of the pixels on the light background side a little lighter and some of the table pixels near the transition a little darker; this helps your eye detect the edge. Unfortunately, the camera will also attempt to "sharpen" the random noise that is produced at ISO 800; making it worse. Shoot at soft and your shots will be a LOT smoother

 

Tip #2 Overexpose a little bit

Theory:  The reason that this helps is simple noise theory. The more signal, the less noise. At ISO 800 the camera has the gain on the CCD cranked up so far that a lot of random noise is introduced. You can see this in a typical ISO 800 shot; the worst noise is in the shadows. To compensate for this, you can give your picture a little more signal. Yes, in some situations you can't do this, either because you just don't have enough light and that is the reason you are using ISO 800 in the first place, or because the reduced dynamic range at ISO 800 means that you are already in trouble with the highlights, but usually you can get away with using at least +0.3 EV. Note that there is no point in using +1.0 EV compensation; that would be a factor of two in light, and you might as well have shot the shot at ISO 400 then and avoided all this if you use +1 EV. Using +0.3 EV gives you a little less noise while still retaining most of the ISO 800 speed benefit.

Tip #3 use 1600x1200 mode.

Theory: Using this mode results in the camera "averaging" out the noise for you. ISO 800 is so noisy that you aren't really losing much detail by doing this, so try it. Using this mode averages every 2.5 pixels into one pixel. This trick has been used for a long time by certain cameras, and is still used today. For example, the old Pro 70 would only let you use high ISO (400) in half size mode (about 750x500). A modern camera that does this is the Fuji 602; it only allows ISO 800 and 1600 at half sized mode of 1280x960; the camera forces you to use the reduced mode. Fuji even has a fancy name for doing this like "pixel averaging"; it is nothing more than resampling. With the D7 you have a choice, and the 1600x1200 mode is a good compromise between noise and resolution. Sure, you can use the 1280x960 mode if you want to; but there will be some loss of resolution at that mode.

 

Tip #4 Set increased contrast

Theory: One of the reasons that ISO 800 shots look bad is that they have an overlay of random noise. Yes, this gives you the speckled noisy look, but the other problem with it is that on the average it brightens the entire picture. Since the noise is present in all color channels, the effect of the random noise is to add an average value of (say) 10 or 20 to each pixel value; this appears as a sort of washed out look. By setting +1 or even +2 contrast, you can compensate for this and improve the look of your shots. You should only do this if you are using Tips 1-3, or you will just make the noise look worse.

 

Examples:

Here are some real world examples. First, an ISO 800 shot at the default settings.

http://www.pbase.com/image/1711972.jpg

Next, the same scene with Tips 1-3 soft sharpening reduced size and +0.3 EV

http://www.pbase.com/image/1711975.jpg

Next the same scene with Tips 1-3 and +1 contrast

http://www.pbase.com/image/1711975.jpg

 

And lastly with Tips 1-3 and +2 contrast.

http://www.pbase.com/image/1711981.jpg

This last scene isn't too bad! Yes there is still some noise, but compare it to the original; no real detail is lost, and the image could be printed 4.6 or 5x7 with good results.

The original samples are available in this album; you may want to look at the full size originals to get a better impression of the noise.

http://www.pbase.com/brachiopod/d7_iso_800_test