Need help understanding DSLR zoom

chump1979

chump1979

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Having always used pocket camera where the zoom is defined as a multiplyer - moving to a DSLR i'm finding it difficult to get an idea in my head what different telephoto lenses might give me in terms of actual zoom compared to a regular camera which has a '10 x zoom'.

I'm hopefully going to be buying a 70-200mm Canon L series telephoto lens. What i would like to know is just how much 'zoom' the lens will give me at 200mm to make sure i'm going to have enough zoom! It will be used on a 40d.

Ideally if someone has a photo with no zoom then the same photo at maximum zoom on a 200mm lens that would be great!

Thanks! :woot:
 
Well the 'zoom' of the 70-200mm would be just under 3x, the same with a 24-70mm, zoom just means the difference in magnification between the shortest focal length and the longest focal length. :)

What you really want to look at is magnification I think. In that 50mm is supposed to be what your eye sees (ie. it would be the same size through a 50mm lens as it would be just looking normally) so a 70-200mm would be around 1.5-4x larger in the screen than with your eyes.

I'm not sure how the crop factor affects that though.

I hope that helps a little :)
 
It can get very confusing comparing a compact camera with a 10x zoom and a modern DSLR with interchangeable lenses.

The zoom ration is simply ration of the shortest focal length to the longest. Canon do produce 10X zooms the 20-300 mm being a example .Yours for £1600 or thereabouts (and weighs 1600gms as well).

So how much zoom will you get with the 70 -200 lens ( Good choice by the way). Well the crop factor has an effect. You are only using the center of the lenses image compared to a full frame camera. This gives the effect of increasing the focal length compared to the image on a full frame camera. This means that a full frame camera would need a zoom lens of 112mm -320mm to give the same image as your 70-200 on the 40D. effectively you get more telephoto for you money on the 40D.

As to is this enough only you can answer. best advice I can give is get to a good Canon dealer who has one of these lenses and try it on you 40D. It's the only way you can tell.
 
You can't compare between the two without a frame of reference. The compact camera still has a focal length that might start at 28mm and go up to 280mm (10x). What you need to do is find out what the 35mm equiv. of the compact camera lens is and then you will have a frame of reference to compare results.

Most reviews and some shopping sites will give the focal length for full frame 35mm so just do a search for the camera and you should get lucky.
 
Find out what your compact cameras 35mm equivalent focal length is (eg 35-350mm, 28-280mm etc). Divide it by 1.6 (22-220mm, 17.5-175mm).

If your camera has a 10x wide zoom lens going from 28 to 280mm (eg the Panasonic TZ3), then to have the same zoom range on a 40D, you'd need to get a lens with a zoom from 17.5-175mm. The closest to that would be an 18-200mm lens. In your example of a lens you want, the 70-200mm lens would go a little beyond what your 10x zoom camera already does (if it's a wide zoom).
 
I found, when i first started, the esiest way was to convert the 10x zoom on my bridge to relative MM numbers, so that I could get an idea

for example, my old olympus was 38 - 380 ( giving its 10x zoom)

the first lens i bought was a 70 - 300 (105 - 450 if you take the crop factor into account)

now whilst that is only 4.3x zoom, if you compare that to the max magnifaction on the olympus, it was like having a 12x zoom (if you get the drift) max magnification

seems a bit complicated now as I type this, but it worked for me.


the sooner you forget about zoom factors and start thinking focal length, the easier it will become
 
Since a picture paints 1,000 words here's one I did 3 years ago to find out what zoom range I had then. It's a 28mm and a 400mm perspective from the same point of view:

Zoomtest28mm-400mm.jpg


That 'Newport' entrance is at about 400 meters distance (a quarter mile).
 
thanks - that's just the sort of comparison i was looking for to help me make up my mind of just how much 'zoom' i'd like. thanks :)
 
chump1979 said:
thanks - that's just the sort of comparison i was looking for to help me make up my mind of just how much 'zoom' i'd like. thanks :)
Click to expand...

You mean how much wide angle and/or telephoto angle you like. 'Zoom' means range. Not focal length.
 
W.Smith said:
You mean how much wide angle and/or telephoto angle you like. 'Zoom' means range. Not focal length.
Click to expand...

sorry yes i do understand what you're saying just not sure on the terminology to use currently so i stuck in 'zoom' as it was easiest.

Anyway I'm getting excited now as I am about to order:

Canon 40d
EF-S 17-55mm f2.8 IS USM
EF 70-200 f2.8 L IS USM

LOTS of money :eek:

If i need the extra reach that the 100-400 would have given me in the future I'll probably just get an extender.

Thanks :)

Marc
 
probably not but the way i see it - if i have good equipment from the outset it means i don't have to upgrade in a year or so.... i've always lived with the notion that jumping in at the deep end is the best way to learn...rightly or wrongly!
 
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