Digital camera terminology

[Rifleman]

I feel I see a popular misconception on terms with digital camera lenses......when a camera is referred to as having a 10x optical zoom, it doesn't necessarily mean that you'll see things 10 times closer than normal....all it means is that you will have a range from your wide angle setting of whatever that may be, to your full zoom....

eg 1: If you have a 35 mm camera, the normal 1x lens is roughly 50-55mm.....100 mm would be two times magnification,......but if you get a zoom lens for the same camera which may be a 35-105 mm lens then the zoom power is 3x but the actual power of magnification is ony two time normal.....don't miss on this one, it may lead you astray when you seek out a zoom.....

eg 2: For my old 35mm camera I had an 80-200 mm lens which was 2 1/2 times zoom (80 x 2 1/2=200) but gave me a 4 power increase in magnification over the normal 55mm lens......(200 divided by 50=4)

Simple arithmatic can help to solve this if you remember the old numbers from 35mm photography.....50-55 mm focal length is 1x normal viewing (not exact, but close enough for most of us amateurs)
Zoom range doesn't always mean magnification power....

[Hagar]

OK, maybe I can add my two penn'orth as a complete novice who knows very little about photography. When I decided to go for my first DSLR I was mainly interested in what size zoom lens I would need to get reasonable photos of aircraft at air displays. Unfortunately at most public air shows in this country the display line seems to get further away every year & I soon found out that the 55 - 200mm lens I decided on was not going to be man enough. Bear in mind that a 200mm lens on a digital camera is relatively more powerful than the same lens fitted to a standard 35mm camera so in theory at least this worked out as 320mm. This is perfect on the approach at Shoreham & at Old Warden where I can get up close & personal but not for the average air display. I've taken some excellent photos with it but it's just not powerful enough.

The display season is just taking off & rather than miss out I decided to cut my losses & go for a budget 70 - 300mm lens. (At a conversion factor of 1.6  for my DSLR this actually works out at 480mm in digital terms but it's still a 300mm lens.) My main problem so far is camera shake resulting in blurred images but a stabilised lens is way beyond my budget, as is a faster one with a bigger aperture. We shall soon see if I've made the right decision.

[Craig.]

take both lenses doug, if you dont feel your getting good results with one, you still have the other at least.

[killerbunny]

... My main problem so far is camera shake resulting in blurred images but a stabilised lens is way beyond my budget, as is a faster one with a bigger aperture. ...decision.

The rule for shutterspeed and focal length is : shutterspeed = 1/focal length
So when using a 300mm lens, the slowest usable shutterspeed you can use for shooting out of free hand is 1/300. ( 1/200 for 200mm, 1/100 for 100 mm and so on...)
If you need slower shutterspeeds you should use a tripod for more stability.

[Rifleman]

.........this actually works out at 480mm in digital terms but it's still a 300mm lens.) My main problem so far is camera shake resulting in blurred images ........

So, for what I'm reading now about blurred images, you're going to have to shoot at a shutterspeed of 1/500th or faster and still overexpose about one stop for the dark object in a bright sky (spot meter will help) .....if you need more aperture help, then move up your ISO to 200 and see if you can get to the exposure value which you're seeking ........

[Hagar]

Thanks for the tips chaps. Weather permitting I shall have plenty of chances to try them out this weekend. Of course, a little sunshine will make al the difference.

The rule for shutterspeed and focal length is : shutterspeed = 1/focal length
So when using a 300mm lens, the slowest usable shutterspeed you can use for shooting out of free hand is 1/300. ( 1/200 for 200mm, 1/100 for 100 mm and so on...)

Thanks killerbunny. Just what I need to know. That's very useful advice indeed.