zoom? does it exists?

[cronnin]

I am talking about optical zoom on digicam, like Canon-powershot.

When I look through the optical viewfinder with my right eye, but leaving my left eye opened , I can see two different-sized objects with each eye. The thing is that they are are the same size when the zoom is set to maximum, and right-eye object size is decreasing when decreasing the zoom on the camera.

That means that camera has no real magnifying capabilites, but it can only zoom out 3 times (if the zoom is stated to be 3x). Is that correct?

[Jon]

What you see through the optical finder on, say, an A620 isn't exactly the size of the image you capture on the sensor. Further, when you print the image out, it's generally further enlarged. If you were to look at the LCD display, which reflects what the sensor captures, you'll see that the area captured by the sensor is magnified compared to what your eye sees.

Describing a zoom, however, as 3x, 4x or 12x is strictly a marketing ploy. It merely describes the difference between the shortest and longest focal lengths can achieve. It doesn't tell you how much the total maximum magnification of a lens is. Moving from the PowerShot line to the EOS SLRs, where there's a greater variety of lenses, will illustrate this. Take a 4x zoom. Canon has several 4x zoom lenses. There's the 75-300 mm EF and the 100-400 mm EF L. Maximum magnification of the two isn't the same; the 100-400, with a 400 mm maximum focal length, can enlarge distant objects more. But then, so can a 400 mm "prime" (fixed focal length) lens. It's just a 1x zoom in marketing terms. The A620 also has a 4x zoom; this one's a 7.4-29.6 mm zoom. However, when you consider the angle of view (due to a smaller sensor), it's equivalent to (it "sees" the subject the same way as) a 35-140 mm lens on a 35 mm camera.

By comparison, your eye, related to a 35 mm camera, is roughly equivalent to a 40 mm lens in the 35 mm format(for the area of best vision); when you
include peripheral vision, it has an angle of view roughly that of a 20 mm lens (this varies fairly widely among people), however the quality of that peripheral vision is nowhere near as good as the central zone of vision.

So there are two things here - the lens' "magnifying capabilities" have to be viewed relative to the actual capture and to the prints we later view. Then there's the "zoom ratio", which isn't terribly useful to anyone but sales people.

[cronnin]

Ok then, if I have a camera with a great zoome, like Canon S5 or FUJI S5600 (something like 10-12x zoom) will I be able to read the newspapers that are 100 feet away on its LCD or not?

[SaNdMaN82]

Ok then, if I have a camera with a great zoome, like Canon S5 or FUJI S5600 (something like 10-12x zoom) will I be able to read the newspapers that are 100 feet away on its LCD or not?
Mmm... well, i dunno about the lcd part... But, sure you will be able to read those in a normal monitor.

here is a example of that:

http://img106.imageshack.us/img106/4285/img0878copyes2.th.jpg (http://img106.imageshack.us/my.php?image=img0878copyes2.jpg)

the link points to a photo i took a while ago, with an s2... the girl was at about 20-25 meters away from me. The exif of that photo, states: "Focal Length: 49.6mm". (the pic has been resized and due to the upload restrictions at imageshack, but the square part, is a 100% crop of the original one)

These cams have a range of 6 - 72 mm, being 12x 72mm of course... So, if my maths are correct, that photo was taken at 8-9x.

As you can see, the title is pretty clear (in spanish though), and the text... well, it's a very small font anyway...

so, summing up... optical zoom is a lovely thing, and it surely works... but, the lcds in these cameras are tiny, compared to a pc monitor... we are talking about 10-12'' of difference. I think you should be able to do what you say, if you zoom 100%, even with the cam... but, if that fails, as you can see, using a computer monitor changes the situation...

hope i've helped ;)

[Jon]

As I said "10x" is meaningless - it's not magnification, like 8x is in binoculars; it's the ratio between the shortest and longest focal lengths the lens can reach. And whether you can read a newspaper at 100 ft. will depend also on how good the resolution of the LCD and of the camera's sensor are.

[cronnin]

As I said "10x" is meaningless - it's not magnification, like 8x is in binoculars;

Yes, thats exactly what I wanted to hear...I was thinking something like that, but I wasn't shure. The comparision with binoculus was awesome.

Thanx.

I will do a little research on light refraction and lens geometry, and maybe I'll be back :)

[madmmac]

Having more than a few zoom and prime lenses for my 35mm, what I seem to find is that right around 70-75mm is generally the same proportion of what my eyes actually sees.