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Old Apr 26, 2003, 9:34 AM   #11
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Let's start with the last question: Yes, I used the F707's 35mm equivalency as an example because you mentioned that you had this camera.

Your assumptions for the size of the F707's CCD are approximately correct - the actual dimensions of the CCD are published by Sony and available on the web.

Yes, you would want 380mm assuming that field of view was your interest. Equivalent depth of field would be less on the larger sensor because of the real versus equivalent focal lengths. The relatively tiny sensor in the F707 in essence acts like you were cropping a tiny portion of an extreme wide angle lens in 35mm terms. The true focal length is very short as you now know. The apparent depth of field with the fixed lens, small sensor cameras, is much greater than on a full sized 35mm lens with a true focal length equal to the "equivalent" focal length of the smaller sensor.

There have been several fixed lens digital camera's made with 10X optical zoom. Among them are the Olympus C2100UZ and E-100RS, and the Canon Pro 90. In the world of the 35mm camera (or for removable lens digital SLR's) there are not too many 10X optical zoom lenses made. Canon has one, but the "best" one made, to my knowledge, is the Sigma 50-500mm zoom. It's very difficult to maintain optical quality through such an extreme focal length range, but Sigma have managed to beat the odds with their very excellent 50-500.

Best regards,

Lin
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Old Apr 27, 2003, 12:41 AM   #12
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Quote:
Originally Posted by Lin Evans
There have been several fixed lens digital camera's made with 10X optical zoom... It's very difficult to maintain optical quality through such an extreme focal length range...
If it's difficult, why have the digital (fixed lens) cameras with 10x optical zoom been able to get away with it? Or have they not really done it that well?
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Old Apr 27, 2003, 1:23 AM   #13
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Substitute "costs too much" for "difficult" and you have the answer. Engineering a higher resolution long focal length zoom would put the camera way beyond the cost/benefit ratios of competitive products. The lens alone would cost more than the entire camera does now if it were engineered to work with a four or five megapixel sensor. The sensor size would have to be increased, the lens would need stabilization or the user would have to use a tripod with anything beyond about 8x, and the quality of the lens itself would have to be measurably better. In the end, it's all about money. It was "possible" to do this with a 1.5 and 2 megapixel camera. It was more difficult with a 2.6 megapixel (Canon used a 3.2 megapixel sensor, but could only get 2.6 megapixels without vignetting), and since it's been more and more expensive.

Compare the cost of a Nikon 5700 with a 4500. That extra megapixel and long zoom more than doubled the price and required a totally different lens system. Panasonic now has a 12x optical zoom camera on the horizon. I've looked at images from it, and there is excessive chromatic aberration at full zoom. Will it sell? Who knows. It's not going to be easy to market it.

Lin
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Old Apr 28, 2003, 5:37 AM   #14
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Ah, I see.

So you basically want to have at least two lens with an SLR (digital or otherwise): your wide-angle lens, and your telephoto lens. You don't really have a "normal" one, do you? I mean, not if you want a lot of zoom power.

BTW, is 380mm an uncommon size for a zoom lens? If I had a Canon Digital SLR (a camera I want to get in the future), what does a roughly 380mm lens cost? (I guess with some of them, because of the 1.6x multiplier, I could use a 238mm...) I'm not familiar with SLR stuff at all, so I don't know how much lenses go for. I saw something the other day that listed a lens alone being like $1,000. Which is pretty intense. My whole camera listed for that price!

Thanks again.
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Old Apr 28, 2003, 5:45 AM   #15
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And in looking at some of these SLR lenses, I see F-stops listed on them. Why are they so limited? On my camera, for example, I can go from F2.0-F8.0. I thought this was common. Some of these Canon lenses list F4.5-F6.0. That's pretty limited. Is the kind of apeture flexibility I've got on my camera a result of it having a small CCD (relatively speaking) or because it's a fixed lens camera?

Thanks.
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Old Apr 28, 2003, 8:17 AM   #16
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Hi Robert,

It would really help if you were to find a book on basic photography and read up on the principles of aperture (F-stop), focal length, etc.

Lenses come in two basic flavors - zoom and fixed focal length (also called prime lenses). A zoom lens usually varies in the amount of light it can gather with more light being available at wide angle and less at telephoto. Don't confuse this F-rating with the aperture which controls how much of this available light actually reaches the film or sensor.

Even if a lens has a rating of F1.8 for example, the aperture can be closed down to a tiny hole and admit only enough light for F/22, etc.

You need to study principles like "diffraction, aperture, f/stop, focal length," etc., to get a better feel for what is going on with the camera.

Costs of lenses vary from around $80 to as much as $80,000 depending on the focal length, size and quality of the optics and physical construction. It's not really possible to give a price for a particular focal length lens without knowing all the relevant details. If you want to get a better feel for it, go online to a company like B&H in New York and scroll through their available 35mm lenses. By doing this you will get a better idea of the range and cost of different lens configurations.

Best regards,

Lin

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Old Apr 28, 2003, 3:43 PM   #17
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Thanks for all the info. After I posted, I scrolled around B&H's web page (funny coincidence) and saw that most of the Canon EF lenses were $250, $500, or $1,200 is price (give or take a few hundred). I also saw those "prime" lenses--that'd certainly take some getting used to!

Yeah, I need to take a photography class. The thing I worry about is that if I do, they'll spend more time on the darkroom (which is pretty much useless to me since I have a digital camera--yeah Photoshop had some similar stuff, though) than on shooting techniques and camera theory, which is what I'm interested in. I went to talk to the local college's photography teacher, but I missed her the one day I managed to make it to her office. Maybe this summer--who knows.

I suppose I could get a book, in the meantime...

This photography hobby is even more expensive than my car hobby!
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