Sensor size and diffraction.

I had some hard time following the discussion here so I had to look elsewhere and found a nice site explaining the relation between diffrakcion, sensor size/pixelsize and aperture in an easy to understand way I think.

http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

Very easy to find the limits of your camera.

Erik Ohlson wrote:

There is nothing magical about this - but where the "Magic" comes in is that - due to physics again (sorry!) when light passes through a hole, it "scrapes" on the edges. All waves do this, including light and water. Here is a picture of water waves passing through an aperture, notice how the wave pattern changes and smooths (blurs) out.

It does because the energy spreads over a larger area. Diffraction can be explained by interference patterns barely visible here. On the other hand, it is the "scarping" (not really a scraping) causing the interference patterns.

The waves are coming toward you in this photo:

View: gallery page

When light does this, it blurs the image. It's called "diffraction". It can NOT be avoided.

The wider the hole, the less blur.

Erik Ohlson wrote:

"Hmm, I wonder if my better pics were taken using A mode...

Now I need to experiment. Thanks for the comment (should have read all the posts earlier!).

It is very likely that this is, indeed, the case.

"A" mode is the best for any of the pocket zooms, by any manufacturer.

It's technical - physics, actually. The sensor is quite small, therefor the lens must have a very short focal length - usually about 4.3mm (that is approximately 1/3inch).

The 'aperture' is the "hole" the light comes into the camera. The aperture can be changed, and the numbers used to keep track of this are the RATIO of focal length to the size of the opening. (Divide the size of the opening in millimeters into the focal length in millimeters = the "ƒ/number" value.

There is nothing magical about this - but where the "Magic" comes in is that - due to physics again (sorry!) when light passes through a hole, it "scrapes" on the edges. All waves do this, including light and water. Here is a picture of water waves passing through an aperture, notice how the wave pattern changes and smooths (blurs) out.

The waves are coming toward you in this photo:

View: gallery page

When light does this, it blurs the image. It's called "diffraction". It can NOT be avoided.

The wider the hole, the less blur.

There is a critical size "hole" for visible light - approximately 3mm (1/8 inch).

This 3mm hole happens to be about ƒ/3.3, and going smaller than that (larger number - yes, its confusing) the blurring effect gets much worse.

So setting the Aperture to ƒ/3.3 and LEAVING IT THERE will ensure the sharpest image the lens is capable of. Period.

There is no "downside" to this: the camera will then choose a shutter speed (from 1/2000th second right down to 1 full second). This "wide open" aperture is best for "low light" too - it lets in more light.

When you zoom out, you will see larger ƒ/ numbers although the actual "hole" remains the same, the changing numbers are just how many times the diameter is divided into the focal length - which is changed by zooming.

Forget all you have ever heard about "stopping down for depth of field" - with this extremely short focal length you have extremely deep depth of field (Physics again, sorry).

Once you become more familiar with photography, you can use different apertures at the long zoom focal lengths where the diffraction effects do not apply. (Yep, physics, again.)

So, set it on "A" mode - about -.66 EV is a good idea to control the brightest parts of the picture and improve the general appearance of your images, and the camera takes totally automatic pictures by changing the shutter speed.

That's all you really need to know for using this type of camera.