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blister Sep 7, 2008 10:32 AM


I don't understand what causes the firestation bricks in Steve's sample pictures to sometimes run together in 'bands'. It's as if the camera has singled out darker bricks or something and related them. I'd like to know what causes it and whether it can be used as a tool in judging quality in some way.

I've also been thinking about the difference in reviewers opinions of the same camera. For instance, it's quite common to find that a camera has little purple fringing in one review whereas another will find quite a lot more. Would this be down to manufacturing variation in the quality of the components of the camera, or something else?

Good site and forum, by the way.

JimC Sep 7, 2008 2:51 PM

I'm not quite sure I follow you...

If you're not looking at the full size originals, you may be seeing moiré or other issues caused by resizing (and with some browsers, after you click on the thumbnail, the browser is resizing them to screen size, so you have to click on that resized image to see the full size original). Different image viewers and browsers are going to have different resizing algorithms, and sometimes they can cause those kind of issues.

Purple fringing is usually lens related (or the way a given lens interacts with a given sensor), and sometimes stopping down the aperture (higher f/stop numbers) can help out. Some lenses have more issues at some focal lengths and apertures compared to others, too (i.e., may be worse the at widest or longest focal lengths with some lenses, and is usually more evident at wider aperture settings). It also tends to be more visible in high contrast areas of an image (for example, a darker edge against a light background or vice-versa).

blister Sep 7, 2008 5:30 PM

Sorry Jim, I was stupid over my first question. I didn't realise that I could click on the full size image in Steve's sample pictures to get a much better resolution. That has now made all the difference.

My second question is, I suppose, about the manufacturing tolerances of digicam construction. I just get puzzled by the wide differences found by reviewers, both pro and user, in the same model of camera. Maybe inbuilt preferences, user ineptitude, and sheer luck account for this.

Thanks for your reply.

JimC Sep 7, 2008 5:35 PM

You've got a lot of variables involved. The subjects and conditions a photo were taken in, amount of contrast in an image, time of day and position of the sun in the sky from where you are shooting, focal length used (how much optical zoom), and more impact what you get when you take a photo. Even waiting until a cloud rolls over can have a big impact. Roll your mouse over the first image in this short article for an example of that:

blister Sep 7, 2008 6:37 PM

Heavens, that link and shot is interesting! Thank you very much for your help in this. I can see that I have even more to learn than I thought.

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