What 'compact' digicam to buy?

12 replies [Last post]
Tunni
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Joined: Aug 9 1999

Similar to Toms post but. I want a snapshot camera that will fit nicely in a pocket. There are so many makes/types I'm confused and they have tiny bits of glass! (lenses!!)

Now call me old fashioned but is the quality of these up to much? and how sensitive can they be if only letting in such a small amount of light!

Any help/advice greatly appreciated.

Tunni

Stuart B-M
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Joined: Apr 6 2001

Dear Tunni,

What sort of price are you looking to pay ?

Kind regards

Alan Roberts at work
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Joined: May 6 1999

Call me Mr. Picky, but the tiny optical bits are almost certain to be plastic these days. That doesn't make them rubbish, it makes them lighter and cheaper than glass and easier to mass produce.

Christian Lett
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Joined: Apr 26 1999

Hi,

I'm trying to get a Canon Powershot A40, which is a 2 megapixel camera for about £250 but Jessops don't seem to have any in anywhere! I need to buy from Jessops because I've got a Canon USM 28-80 lens to trade in (my EOS 500N body went kaput beyond economical repair) and they'll give me £36 for it.

It's a pretty good camera, despite the fact that there are higher res cameras available, and will fit snugly in a pocket. The same spec IXUS V2 is about £150 more but is much smaller and nicer looking.

Goto http://www.steves-digicams.com for very detailed reviews of most digital cameras available, including sample images from each.

Christian.

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com

tom hardwick
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Joined: Apr 8 1999

It's a common mistake to think that small lenses are only letting in tiny amounts of light Tunni. The information you need to look for is the maximum aperture, and this is not somethingg that you can deduce from looking at the size of the front element or reading the filter thread diameter.

tom.

JMCP
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Joined: Nov 21 2000

Hi,

I know you said you have a Canon lense to trade-in but amazon.co.uk along with a few other places do the Canon A40 for £199. Good luck.

Alan Roberts at work
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Joined: May 6 1999

Yep, F number is what counts. And that's controlled by the physical size of the aperture and the physical size of the image. Make the image smaller and the opeining can get smaller for the same F number. And so on. O level physics.

Alan McKeown
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Joined: May 9 2001

Alan & Tom,

Surely, in the sense that Tunni means, (ie. the common-sense and the physics viewpoint) a “small” lens does indeed let in a proportionately smaller amount of light as compared to a “large” lens.

This must mean that a smaller format camera is either less sensitive than, or has inferior resolution to, a larger format camera, other things being equal.

To take a specific example; consider a “35 mm” format camera compared to a “3.5 mm” format camera.

The “normal” lens focal lengths for the two cameras. would be something like 50 mm and 5 mm respectively.

If we use each camera to picture the same scene from the same viewpoint at the same F number and the same exposure time, then the 50 mm / F2 lens will pass 100 times as much light energy as the 5 mm / F2 lens.

The larger camera image size is 100 times the area of the smaller camera image, so the exposure per unit area is the same in both cases.

However, if the smaller format camera is to equal the resolution of the larger, the light-sensing elements must be packed 10 times more densely in both horizontal and vertical directions to give the same total number of elements as in the larger format. Each element must therefore be less than 1/100 of the area and must receive less than 1/100 of the photons. Ie. the smaller format camera is much less sensitive than the larger.

Alternatively we could keep the individual sensor element size the same for both formats in which case the resolution would be degraded by a factor of 10 in both horizontal and vertical directions.
Or of course some combination of sensitivity and resolution reduction.

Fortunately for the digital camera, the “quantum efficiency” of CCD sensors is very much better than that of photographic film emulsions (by a factor of 50 or so), so small format digital cameras can compete with larger format film cameras on sensitivity.

Alan

Alan Roberts at work
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Joined: May 6 1999

Gentlemen, attention please

What matters in a camera is not the amount of light, but the light intensity at the detector surface. That is controlled by the lens aperture as an F number, rather than the linear dimensions of the lens. Two cameras using lenses with the same F number but having different size sensors will have physically different size lenses but the illumination of the sensors will be exactly the same. So the sensitivity is not dependant on the format size. It depends on the quantum efficiency of the conversion material (usually silicon) and that's a constant among these things.

Stephen Carter
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Joined: Nov 18 1999

This has got a bit technical chaps. To answer the original question the reviews seem to come down in favour of Canon digital IXUS in the resolution stakes. A number of the compacts are pretty poor in this department including the very small and attractive looking Sonys. The larger Sony S75/85 are brilliant but not quite so small.

Stephen Carter
www.seraphmedia.org.uk

Christian Lett
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Joined: Apr 26 1999

Bought an A40 yesterday on line for £205 with free postage (QED) - should be here today! Apart from the fact that it doesn't look as sexy (or isn't as small), it's virtually the same spec as the IXUS models.

It'll certainly do fro me, anyway, as I'll be using it mostly for website content.

Christian.

Christian Lett After Effects and Maya Artist www.quarterlightpictures.com

Tunni
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Joined: Aug 9 1999

Hey Guys!

Interesting points raised! Special thanks to Steven Carter for the metaphorical slap, in trying to answer the question. And I have to add that, as an intelligent person educated to Hons degree level, I am always humbled (and sometimes/often confused!) by the forum genius Alan Roberts. I love reading his answers, how can one human being know so much! I am actually starting to think he is just a super computer, that responds automatically to the posts on this forum!!

...Alan, I'm sure that physics can explain, perfectly why a small size piece of plastic can be equally as good if not better than a large and perfectly ground piece of optical glass...but (and remember sticking your fingers in your ears and doing this as a kid) Ner ner nah ner ner nah nah nah nah dah di dah dee di dee blah de blah!!!!

Tunni

Alan Roberts at work
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Joined: May 6 1999

Cheeky sod

Don't mock plastic, optical plastic is exceptionally good these days, resolution loss isn't the problem, it's flare and contrast handling. Good design can find ways around that. There are lots of compromises in designing a good lens, in video some of these can go (like keeping the image magnification constant when focusing). Panavision zooms don't make those compromises, you can frame up a shot ans focus, and thye image size doesn't change at all. But then, for £100k, I would expect no less.

And when I retire, I'll tell you much more about how I come to have access to all this (hint, it won't be long now).