camera zoom - optical

  dje 17:10 05 Jan 2004

Could someone please explain in laymans terms the difference between pictures taken at 5x zoom and 10x zoom, for example if I was taking shots from the sideline of a football pitch - how far away from me to the other touchline would each zoom capture the action (approximately)
Is 5x zoom enough to take photos of action half way or less or reach the other side or 10x reqd thanks

  Gongoozler 17:33 05 Jan 2004

Sorry dje, it's not as simple as that! 5x or 10x tells you the difference between the angle at maximum and minimum zoom, but the manufacturer can choose what either extreme is. The standard 35mm camera has a lens with 50mm focal length, and this will give an angle of view about 40deg across the 36mm picture width, which roughly equates to the human eye, and so results in a natural looking picture. Zoom lenses for digital cameras will often be quoted according to this 35mm equivalent. My Sony DSC-P71 has a 3x optical zoom, with a 35mm equivalent narrow angle of 117mm, which is slightly tighter than half the 35mm standard (117/50 = 2.3). If you can tell me what scene width you want to cover at what distance, I'll tell you roughly what 35mm equivalent you need, but it's always a good idea not to zoom too tightly then you can do the final trimming on your computer.

  Stuartli 17:47 05 Jan 2004

A simple way is to regard a 2x zoom setting as bringing your subject to halfway between you than at the standard setting; 3x will be a third of the distance etc. You are magnifying the subject the more you zoom so obviously less and less of the surroundings will be included.

The easiest way to find out is to operate the zoom lens on an SLR camera if possible - this will also illustrate Gongoozler's point about how the perspective changes as you zoom from a fixed point.

  dje 18:50 05 Jan 2004

thanks for replies mainly shooting lacrosse action pics at a distance of approx 10- 20 meters upwards I would like to get good close ups from the touchline thanks again

  Gongoozler 19:56 05 Jan 2004

Hi dje. The mathematics is fairly simple, but as I'm about the least sports-minded person in the country I don't know the figures to put into the maths. To a reasonable degree of accuracy if you divide the distance between your camera and the sbject by the width of the subject, the ratio should be roughly the same as the effective focal length of the lens divided by the effective width of the sensor. So if you want to shoot a scene 4 metres wide at a distance of 20 metres, the ratio is 5:1. If your 35mm effective sensor width is 36mm, the focal length needs to be 180mm, roughly 3.6x zoom beyond the natural (50mm equivalent). You should get this in a 5x zoom camera. If you want your scene at 20m distance to be 2m wide, you will need a 10x zoom camera, but you will find that the focus needs to be very precise, and you will need a steady tripod.

  anchor 20:04 05 Jan 2004

Obviously the closer you can zoom-in the better, especially as you are so far away.

Just as an addendum to the above, if your camera is a digital one, & has high resolution, (say 4 to 5 Mpixel), you can do an sectional enlargement on your PC and still retain good quality. This will, in effect, bring the subject closer. I do this quite often, and obtain excellent results with my Canon S50.

  Pamy 20:53 05 Jan 2004

Just get the maximum optical zoom you can afford.


  Gongoozler 21:02 05 Jan 2004

"Maximum optical zoom", but beware of the aperture trade off. A very long focus lens requires a lot of glass if it is to retain it's f/ no, which is one of the reasons why long zoom lenses are so expensive, or are often of disappointing quality.

  wee eddie 21:09 05 Jan 2004

Most digital cameras have a built in delay before you can take a photo.

I believe that this is something to do with charging the sensor.

Several folk have been quite upset about it not being mentioned in the advertising!!!!!

  Wak 21:35 05 Jan 2004

I would also like to point out that with a 3x zoom you also get a 3x camera shake ( or movement)
which will probably equate to magnifying the standard picture 3 times on the computer.
Therefore if you use the zoom lens always try and have your camera resting on something solid in order to minimise any possible camera shake.

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