Viewing JPEG images

  Mike_R 16:48 09 Nov 2008

I've just tried looking at some JPEG images on my new Sony HXD995 recorder. The pictures are not sharp, the colour is a bit iffy and there is a slight judder. The quality is nothing like as good as on my desktop which is pin sharp with a good colour likeness. What I'm wondering is whether the problem is my old cathode ray Sony 28 inch TV which seems OK for normal use, or whether I can't expect a decent image via a TV.

If the latter, I shall have to invest sometime in a laptop which seems a better bet than continually printing photos and spending a fortune in paper and ink. Any recommendations in a cheap 15.4 laptop with a decent screen, please. I'm not into games but it also might be useful on a boat for navigation.

  Batch 18:23 09 Nov 2008

I suspect the problem is to do with the way the (number of) pixels that make up the jpeg image are mapped [e.g. extrapolated (= stretched) / interpolated (= compressed)] to fit your TV screen.

  Mike_R 18:32 09 Nov 2008

Thanks. What I'm wondering is whether this jpeg pixel problem affects only my particular TV or whether it is common to all TVs.

  Technotiger 18:41 09 Nov 2008

It applies to all old TV sets.

  Technotiger 18:45 09 Nov 2008

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  Mike_R 18:49 09 Nov 2008

Thanks again. The idea of a cheap laptop is becoming more attractive.

  eedcam 18:51 09 Nov 2008

At worst it should only appear less sharp than ont he pc partly due to the lesser resolution of the tv and the fact its being considerably enlarged I get no prob a 32 Sony crt.Of course youmay wellbe more critical .Also I usually do mine in a slide show on dvd and the images are optimised for that.Bearing in mind video uses non square pixels and digital images square pixels.

  Mike_R 13:03 10 Nov 2008

I'll try converting the image to a DVD, just for fun. My old TV is a 28 inch CRT and my desktop is a 22 inch LCD. The TV image is crap and the desktop is spot on. I'm only wanting to use the TV because the desktop is not in a good position for showing slideshows in company.

Thinking about it, I really need my TV to break down so that my wife will agree to a new one! Sabotage?

  Batch 14:32 10 Nov 2008

When you view a jpeg on your PC you will either view it at the native resolution of the jpeg (e.g. 1024 x 768) or it will be enlarged or shrunk (e.g. to fit the resolution of your PC's screen). Where the image is enlarged / shrunk, a special algorithm will be used (there are a number of such algorithms, some software evena allows you to choose which one to use).

In very simple terms, where pixels have to be added (e.g. 2 pixels become 3) or removed (e.g. 3 pixels become 2) a compromise has to be made (e.g. where the two pixels are not of the same colour and brightness). These alorithms try to address these issues, but compromise is inevitable and it doesn't always work well. For example, the human eye ir reckoned to me more sensitive to (subtle) changes in brightness rather than (subtle) changes in colour and so the alorithms give weighting to this.

Now, as you probaly realise, jpeg images and your PC screen (and LCD TVs) are fundamentally the same in that they are made up of a grid of dots (pixels).

CRT TVs are not the same (and I'm not the best person to explain), but they are made up of a number of lines (e.g. 625) that are scanned by a cathode ray gun. When your Sony recorder is playing back (via a Scart lead?) it will take the picture and (presumably) try to get it to fit a standard 4:3 or 16:9 (depending on your TV set and set-up). Again there will be some mapping involved and it may be this that is the root of your problem.

I suppose one thing you could try is resizing the images (on your PC) to 625 pixels high before transferring to the Sony - it might help (but then it might not).

  Mike_R 15:19 10 Nov 2008

Thanks again everyone. I think that I'm on a loser for jpegs on the CRT TV, and so I'll stick to the desktop for now.

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