What camera?

General cycling advice ( NOT technical ! )
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patricktaylor
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Postby patricktaylor » 10 Feb 2009, 5:02pm

stewartpratt wrote:... Hm, from reading that I think you may be misunderstanding what decompression is ...

Probably. Many thanks for the explanation. Since I normally talk only to myself about such matters my terminology tends not to be too exact. But as I understand it, when a JPEG is 'Saved For Web' to reduce its file size, the lost data cannot be recovered because the 'compression' is lossy. The original file from which the optimised version was saved needs to be kept separately.

But with, for example, ZIP files, all the data is recoverable. I don't use TIFF files but I understand they are more flexible and also allow 'lost' data to be recovered.

Tom Richardson wrote:(... don't have a go at me or else I will print your message out and hang it on the nail in the outside midden)

Sorry. I wasn't having a go at you (honest).

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Postby stewartpratt » 10 Feb 2009, 5:23pm

patricktaylor wrote:But as I understand it, when a JPEG is 'Saved For Web' to reduce its file size, the lost data cannot be recovered because the 'compression' is lossy. The original file from which the optimised version was saved needs to be kept separately.


Absolutely correct. 'Save for web' is just shorthand for 'use a moderately high level of compression'. 'Save' is generally shorthand for 'use whatever compression the image was last saved with, or the default' - often there's an 'options' button available during the save process if you're saving as a new file. But there's no guarantees as to the exact settings used for either of those actions unless you manually specify them.

patricktaylor wrote:But with, for example, ZIP files, all the data is recoverable.


Yup. Zip compression is lossless.

patricktaylor wrote:I don't use TIFF files but I understand they are more flexible and also allow 'lost' data to be recovered.


Sort of correct - you can't recover lost data, simple as that, but the TIFF format does support lossless compression and it's generally used that way when representing photos.

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Postby skrx » 10 Feb 2009, 5:29pm

If it helps:
My "image" (pretend 0 is black, 8 is white).
0888880
0800000
0800000
0888880
Can be nicely compressed to "Dimensions 7 by 4. 0, five eights, two zeros, one eight, six zeros" etc etc. This is lossless -- you can get exactly the original back from the compressed version. That's good for stuff with big areas of the same colour -- a computer screenshot, a graph, or (standard example) a fax.

Another image:
0123210
1234321
0123212
1234321
The top row is black to grey in the middle, the next row is slightly brighter. That's more typical of a photograph, where there aren't many sharp edges, and brightness changes gradually.
You could describe the "waves": 0 to 3 to 0 horizontally, 0101 vertically. But that's ignoring the extra 2 at the end of the third row for simplicity, so when you put that back:
0123210
1234321
0123210
1234321
You've lost some data. Hence, lossy compression.

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patricktaylor
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Postby patricktaylor » 10 Feb 2009, 5:38pm

skrx, thanks for that. I don't really understand it but it's definitely helped to put me in the mood for dismantling my MTB hubs for the first time ever!

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Postby stewartpratt » 10 Feb 2009, 5:52pm

Heh :)

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Postby ncutler » 10 Feb 2009, 6:58pm

patricktaylor wrote:skrx, thanks for that. I don't really understand it but it's definitely helped to put me in the mood for dismantling my MTB hubs for the first time ever!


Don't dismantle them too often, every time you do it they become less circular ......................

N

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Postby patricktaylor » 10 Feb 2009, 8:07pm

Hummm... (ignorance here). Due to repeated compression, you mean?

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Re: What camera?

Postby PH » 11 Feb 2009, 12:39am

Si wrote:Inspired by the place name thread, I was wondering if there is an ideal camera available that:

Takes pictures that are good enough for the 'net rather than for printing.
Small and light so easy to carry on bike.
Batteries last a long time so don't find that they are flat every other ride.
Tough enough to be chucked in the rack top bag and forgotten about.
Point and click - not faffing setting it up.
Digital so easy to upload.
Cheap because a) I can't afford much & b) is likely to get damaged/lost.
Isn't a camera phone.

Basically, something that I can always have on the bike with me in case I happen to see something interesting (like the buzzard sat in the tree looking down at me as I rode past the other day) and quickly want to take a snap. David Bailey I am not and so don't need anything with bells and whistles, but a bit of optical zoom would be nice if poss. Oh, did I mention cheap?


Back on topic...
With the exception of the optical zoom, you're describing the 2 megapixle camera on my cheap phone. For snapshots on the web I can't tell the difference between that and my 8 megapixel camera.

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Re: What camera?

Postby Si » 11 Feb 2009, 10:51am

PH wrote:
Si wrote:Inspired by the place name thread, I was wondering if there is an ideal camera available that:

Takes pictures that are good enough for the 'net rather than for printing.
Small and light so easy to carry on bike.
Batteries last a long time so don't find that they are flat every other ride.
Tough enough to be chucked in the rack top bag and forgotten about.
Point and click - not faffing setting it up.
Digital so easy to upload.
Cheap because a) I can't afford much & b) is likely to get damaged/lost.
Isn't a camera phone.

Basically, something that I can always have on the bike with me in case I happen to see something interesting (like the buzzard sat in the tree looking down at me as I rode past the other day) and quickly want to take a snap. David Bailey I am not and so don't need anything with bells and whistles, but a bit of optical zoom would be nice if poss. Oh, did I mention cheap?


Back on topic...
With the exception of the optical zoom, you're describing the 2 megapixle camera on my cheap phone. For snapshots on the web I can't tell the difference between that and my 8 megapixel camera.


I've never had a camera phone, mainly because I use my basic mobile about once every 3 months (it's just there for emergencies). How does having a camera on it affect how long the batteries stay charged for?

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Re: What camera?

Postby PH » 11 Feb 2009, 9:13pm

How does having a camera on it affect how long the batteries stay charged for?

I don't know how much power the camera uses. I don't think it's that much if you stay off the flash (mine has a LED light instead of flash, though it's not much good). The most use I've had from mine was a weekend lightweight camping. It was on standby all the time, made a couple of short calls, used as an alarm clock for three mornings, listened to a couple of hours radio and took around 10 photos. The battery had plenty of life when I got home. A spare battery costs about £7 from Ebay, for my use I don't need one.
The phone is a Sony Walkman W810i, it's the only camera phone I've had so I can't compare it to otheers. The reviews highlight the quality of the photos.

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Postby patricktaylor » 11 Feb 2009, 11:00pm

Si. If you happen to take your mobile phone with you (for emergencies) when cycling, then buying a new one is probably a realistic option, given your camera requirements. I don't know if my mobile is a phone with a camera or a camera with a phone, but it's useful as either. (£30-£50)

The last time I looked in Tesco for a mobile that wasn't also a camera, I couldn't find one.

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Postby TwoWheelsGood » 12 Feb 2009, 12:02pm

patricktaylor wrote:The last time I looked in Tesco for a mobile that wasn't also a camera, I couldn't find one.

Try somewhere else other than Tesco :wink:

My local T-Mobile shop had two very cheap phones without a camera (LG and Sony Ericsson), and there are also at least two very basic Nokias without a camera (one with monochrome display and another with colour). Plus there at least one or two much more expensive phones that don't have a camera presumably for those people who regularly work in buildings where cameras aren't allowed.

Back on the subject of mobile phones with a camera, the cheapest new phone I've seen that has a 2 megapixel camera was the Orange New York for £34 (£24+£10 top-up), plus there's a Sony Ericsson T280i with 1.3 megapixel camera for just under £30 including top-up from the Carphone Warehouse.

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Postby rualexander » 13 Feb 2009, 5:07pm

Argos are selling the Canon A470 at £50 just now.
Looks like a good deal.

A review site here :
http://www.steves-digicams.com/2008_rev ... _a470.html

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Postby stewartpratt » 13 Feb 2009, 5:24pm

rualexander wrote:Argos are selling the Canon A470 at £50 just now.


Argh - damn it! - I've been waiting to get hold of a cheap Canon that's supported by CHDK and I thought that was going to be it, but it's not on the list :(

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Postby ncutler » 13 Feb 2009, 5:32pm

Go for the Canon A470 !

There is a website run by an American photographer Ken Rockwell. He's opinionated, forthright, and a delightful antedote to people who keep telling you that you must have all sorts of irrelevant clutter to take decent pictures.

Lokk here to see his recommendations:

http://www.kenrockwell.com/tech/recommended-cameras.htm

... and the 470 is on the list .....

Nick