Comments on the Canon PowerShot S95 camera
Part one: high ISO performance

You probably wonder why my comments on the Canon S95 camera begin with the description of its high ISO performance—after all, one is supposed to start with an introduction, depiction of ergonomics and handling, menus, and so on and so forth. The reason for breaking what has become the traditional sequence of reviewing cameras is that I bought the S95 immediately prior to a trip to Spain and, after a few days with the camera, I had a pretty good idea about its features and performance—with the only exception of image quality at higher ISO settings. On the one hand, this is a compact camera with a tiny sensor, and noise builds up very quickly as you move up the ISO scale. On the other hand, much of it is colour noise that can be dealt with quite easily in post processing; moreover, I quite liked the quality of S95's noise, which is much more film–like than I expected. As a result, I could not quite pin down how far I can go with high ISO settings without jeopardizing image quality too much. Also, simply looking at the shots taken at various ISO settings I could not decide what the upper ISO setting of the Auto ISO function should be. This is an important issue, and I decided to conduct a more formal test to answer these questions before going on the trip.

Below are crops of the same scene shot at various ISO settings shown at 100% magnification. They were processed in Adobe Camera Raw, and what you immediately see is the versions where no sharpening or noise reduction was applied; roll your mouse over the images to see the versions where quick–and–dirty noise reduction and sharpening were applied in ACR. I have to note that the degree of sharpening and noise reduction that I applied was quite mild—many would choose a more aggressive approach. Also, more sophisticated noise reduction software would probably produce better results.

	ISO80		ISO400
	ISO800		ISO1600

Image quality at base ISO (ISO80) is truly remarkable for a compact camera, but by ISO400 there is already a lot of noise. Thankfully, though, it cleans up quite easily and the results are very impressive at this ISO setting, too. The amount of noise increases progressively as we move on to ISO800—there is a noticeable loss of detail and colour data; nonetheless, things still do not look too bad, even though you know that this is probably as far as you want to push it. ISO1600 is very noisy and a lot of detail and colour information is lost to noise. This ISO setting might still work for certain subjects, though.

Pixel–peeping tells only one side of the story; to have the whole story and proper answers I decided to go the extra mile and see what the noise patterns look like in real–life prints. I printed the original photographs at 300dpi first without applying noise reduction and then after cleaning them up a little in ACR.

When no noise reduction is applied, noise is already visible in prints at close examination at ISO400, very noticeable at ISO800, and plain objectionable at ISO1600. When noise reduction is applied, however, the prints look very good up to ISO800, although there is a visible loss of colour at ISO800; luminance noise is noticeable at close examination, too, but it gives an impression of texture rather than objectionable noise. At ISO1600 there is a further loss of colour and detail and luminance noise is very obvious, although, again, it is not too obnoxious and might work for some subjects.

So here is the executive summary based on my tests: the upper ISO setting of the Auto ISO function shall be ISO640; the camera can be pushed further to ISO1600 if absolutely necessary but this should be avoided if possible. ISO3200? You do not want to go there, really.

As with so many things in life, our perception and judgment are based on relative expectations, not objective results (if there is such a thing). Compared with DSLR cameras, high ISO performance of the S95 is mediocre at best. However, the Panasonic LX–2 that I used for years essentially was an ISO100 camera, and I could live with that perfectly well. Now, however, I have a compact camera that I can easily use at ISO640 and, if really necessary, push to ISO1600. Relatively speaking, this is nothing short of astounding.

Continue to part two