Pentax Optio Z10 problems at high ISO

This camera is one of the few P&S cameras that sports a longer than usual 7x optical zoom within the body of the camera rather than extending outside of it. Image quality outside is decent when used at ISO 64 and 100. Indoor flash pictures are good as long as you shoot from ISO 64-200. Above that, noise is quite apparent. There are the usual preprogrammed scene functions for different shooting conditions, including a novel digital wide shot that allows you to shoot two vertically held shots and blend them together into one wide shot a la mini-panorama. The 7x zoom is quite useful and the fact that the lens does not extend beyond the camera makes it one of the smallest with this capability. Here are the complete feature list: http://www.infoborder.com/Digital_Cameras/Pentax/optio_z10.php

Problems:

The only problem I've seen is the marginal image performance indoors at ISOs higher than 200.

what you are seeing is essentially a limitation of compact camera design, and one of the reasons most "serious" photographers end up with a DSLR.

Modern compact digital cameras cram an awful lot of pixels onto a very small sensor, and that is a recipe for high ISO noise.

You can understand why if you think of light using the particle model.

In this model light is considered to be made up of particles called photons. These are just little packets of energy which wizz around at the speed of light.

Think of the sensor in your camera as a series of buckets aranged in a rectangle to catch the light particles. If you have to get 10 million buckets into a sensor 1/4 inch across, those buckets are very very small. Smaller buckets hold fewer photons.

Now, it turns out that all photons are the same size (physicists bear with me here, it's close enough to the truth for this discussion), and you can't cut them up. Further, it turns out that you can't count them particularly well.

Lets imagine for a minute that a single pixel in your compact camera holds 10 photons of light, plus or minus 1 (due to difficulties in counting).

A larger camera has a sensor 10 times the size with the same number of pixels. This cameras pixels will each hold 100photons, plus or minus 1.

The error in the measured value from the small sensor is +-10%, which is what causes noise. The larger sensor has an error of only +-1% giving far less noise.


How does this relate to ISO? simple. To get a higher ISO out of a given sensor you multiply up the results from it. In so doing you also multiply the errors, so that a noisey signal becomes even worse. Add to this the fact that you have to multiply the smaller signals from smaller sensors by larger factors to get the same ISO and you have a one way ticket to noise central.


This is all very simplified, and other factors are also important, but it's more or less correct.

From the point of view of image quality, Pentax and the other camera makers made a grave error in pushing compact cameras beyond 6MP.

@mongoose

great explanation, this is a discussion I end up in quite frequently when people ask me why my bulky ancient camera (ist-ds...) ONLY has 6MP...

99,99% of the people still seem to think that more pixels is better image and that their over sharpened JPEG's from their P&S are much better then my processed RAW images where I adjust sharpness to the scene in question.

thanks Golf, I hope it makes sense!

the ones which really make me laugh are the phone cameras. 5 megapixels in a phone? give me a break!

The really annoying thing is that the consumer drive to push up the pixel counts is hurting image quality. For a while the major camera brands seemed to resist the megapixel madness, but it seems they have now given in. You can't blame them, they have to make what will sell, but I dread the day when my Lumix FX-7 breaks. I just don't know of a current compact camera which can equal its performance.