Bluriness, or fuzziness?.

Blur, at least some of us think, relates to motion. Either the camera moves or the subject moves, and the shutter speed is not fst enough to freeze the motion..

Fuzziness, on the other hand, relates to the lens being focused on the wrong spot, of the elements in the lens not being shaped properly..

For blur, make a huge print and then look for very small points the dot on an I in a sign, perhaps, and study it with a magnifyer to see if it is round, or stretched into an oval..

As for fuzziness "circle of confusion" is an optical term that relates to fuzziness, and is used by scoiientists to decide whether something is within the depth of field..

BAK..

BAK wrote:.

Bluriness, or fuzziness?.

Blur, at least some of us think, relates to motion. Either the cameramoves or the subject moves, and the shutter speed is not fst enoughto freeze the motion..

I don't know whether blur can be measured. But regarding camera shake:.

You could try shooting the same scene with the camera firmly fixed on a tripod, set the aperture to an optimal setting (perhaps one or two stops smaller than the widest setting). Use the self-timer to avoid vibration at the moment of exposure..

Then repeat as a normal hand-held shot, with no particular precautions other than what you would normally do.And then compare the results in detail..

For any single image, you might find it hard to see the difference. But under difficult conditions, (low shutter speed, long focal length), the tripod shot will show definite greater sharpness...

The definitions arent standard. Photoshop Smart Sharpen corrects for Gaussian Blur, Lens Blur and Motion Blur. Focus Magic for Out-of-focus Blur and Motion Blur. The difference between Gaussian and Lens blur isnt intuitively obvious to me, but you pretty much know what they mean. In each case the word blur is used to denote both types. That is the notation I am most familiar with..

With motion blur in Focus Magic you have to give direction, which isnt significant to your question but you have to get it right to measure the pixels. You give the motion in pixels in that direction. For Out-of-focus Blur you apply pixels based on radius..

So for me I guess you could define blur as the number of pixels I have to adjust to get it sharp. Of course a 5 pixel out of focus on a 2Mp image is a lot blurrier than 5 pixel on a 16 Mp image. And I would guess that a 10 Mp image with 5 pixels of blur printed 4 X 6 would look sharper than the same image printed 13 X 19. But then again theres viewing distance ..I doubt theres a standard measurement...

EMoscosoCam wrote:.

Hello.

Can blurness be measured? How can I tell if a picture was taken withabsolutely no blurness?.

Thanks a lot..

There are mathematical descriptions of blur such as convolution and there are ways of describing how good an optical system is to assess how closely it is achieving it's theoretical capabilities..

No picture would be produced without any blur because the imaging system will have diffraction limits to it's performance but the better the optic, the closer it will perform to a 'perfect' instrument. A measure of this performance is the Strehl Ratio (always less that 1 which would be perfect) and if you were to buy a very high end telescope (from TMB, Astro Physics or others), it would come with a test report quoting the Strehl Ratio of the optics that had been found by testing them on an interferometer..

If I had a better understanding of the maths behind it, I would be able to be more helpful but there are precise definitions of blur out there if you don't mind getting stuck into the maths...

Doesn't Popular Photography magazine use some software to measure sharpness/blurriness in their lens reviews? Seems to ring a bell but I haven't read it in quite awhile...

There are two practical sources of blur that might provide a "standard" against which to judge blur. The first is the focus blur at the edge of the depth of field. You can use a DoF calculator to set up a situation and then see how much blur that is. Another source of blur is diffraction blur from higher f numbers. You can take a shot at successively higher f numbers to see how much blur that is. It is a good idea to do this, in any event, to see where diffraction is not a problem with your particular sensor.Leonhttp://homepage.mac.com/leonwittwer/landscapes.htm..