Converting from zoom to mm, or "how close do I get?&quo

[gerolamo]

Hi
I'm yet another new guy that is looking into digital photography. I already own a video cam, zoom 18x and a small digital cam, zoom 2x.
I'm thinking of buying a 4-6mp digicam and a telephoto zoom lens, mostly fot nature and wildlife photo.

Basically I need to know how close I can get to the subject.
I know how close I can get with my 18x and 2x. But how about in mm?
I did some research, and here's my conclusion, which I hope it's wrong btw.

Let's take a Canon Digital rebel, with a lens of 18-55 mm - that is 3x optical zoom.
I take out that lens and put in a EF 35-350mm f/3.5-5.6L USM Canon Telephoto zoom lens. (imagining for a moment I afford it)
So overall, using these two lenses i get a zoom of 350/18 = 19.4x
So from the 18mm wide angle all the way up to 350mm I have an overall zoom of 19.4x.

But the zoom from regular angle (don't know exactly how it's called, but you should know what I'm talking about, when wide angle stops and magnification begins) - 50mm - that will give me a magnification of 350/50=7x

But now, let's take minolta dimade z1.
lens 35 - 350mm. Zoom 10x, again 350/50=7x

For the next part I need some help guys.
I'm starting to think that the approach is given by the focal lens only.
So a 350$ minolta will get me as close to the subject as a 1500$ telephoto zoom lens.
So besides the obvious improvement in quality, I won't get any closer with the expensive version.

And this just can't be. Please tell me I'm wrong.

P.S. on a hunch I looked at my videocam lens setting
F/1.6 - 2.9, 18x power zoom, f= 2.8 - 50.4 mm (don't know how to get the 35mm equivalent)

Now i know I am wrong, because I can read with my camera a licence number at 100m, and that's pretty good.

So how do I find out how close I actually get? I know there must be something else that comes into play, like lens lenght or something but I just spent 2 days searching some details about this and I can't find a clear explanation.

And can you tell me what all those numbers in the zoom lens stand for (EF 35-350mm f/3.5-5.6L for the Canon telephoto zoom lense) or (F/1.6 - 2.9, f= 2.8 - 50.4 mm for my video cam).

Thank you.

[robertwgross]

And can you tell me what all those numbers in the zoom lens stand for (EF 35-350mm f/3.5-5.6L for the Canon telephoto zoom lense) or (F/1.6 - 2.9, f= 2.8 - 50.4 mm for my video cam).


It gets awkward to try to compare still camera lenses with video camera lenses.

If you think of 50mm focal length as the "standard view", then a lens that zooms from 35 to 350mm does offer a ten times zoom factor. However, it is going from a slightly wide view (35) to a very long view (350). A lens that zooms from 10 to 100mm offers the same ten times zoom factor, but it goes from an extremely wide view (10) to a long view (100). The zoom factor may be the same, but the latter lens would not get you the same image that the former lens will get. For extremely long telephoto work, you might need a lens to go out to 500mm.

EF 35-350mm is the range of focal length zoom. Then f/3.5 is the wide open aperture at one end of zoom, and f/5.6 is the wide open aperture at the other end of zoom. A lens with f/1.4 aperture is much more sensitive to dim light as compared to a lens with f/3.5 aperture. A normal lens with f/8 aperture might be junk. "L" is a Canon designation for its luxury low-loss lenses that offer superior optical performance at a luxury price.

---Bob Gross---

[SoCal69]

The best way is to look at the 35mm (35mm here refers to film size, not lens focal length) equivalent focal length of the camera lens. Using 35mm equivalent allows you to have a standard against which to compare different lenses. For example, if the Minolta has 35-350 35mm equivalent range, and that is the range you want, then that is what you need to look for. If you were interested in the DRebel for instance, you would get lenses which span from approximately 21mm to 218mm lenses (this takes into account the DRebel's 1.6x crop factor). It will be different for different cameras. You should just make sure you are comparing them against a base standard. Forget about the multiple zoom numbers, as they really don't give you any significant info.

IF you are looking at wildlife photography, your long end should probably be able to get, at a minimum, 300mm, but preferably much more (in the 400-500mm range). There are many wildlife shooters here who can provide better information on what focal length you need. However, you really should give us an idea of what type of camera you are considering (point and shoot, DSLR, something in between?)

Hope this helps.

[Tom W]

Wouldn't it be simpler to just compare angle-of-view for this purpose?

[SoCal69]

Wouldn't it be simpler to just compare angle-of-view for this purpose?

Now you say this?!?!

Geez, I could have saved myself a lot of typing!

[gerolamo]

Thanks for the input,
It's much clearer now.

What I'm looking for is a semipro SLR with a powerful zoom, and I keep on comparing it to Minolta because I know how close that camera can get me. I'm using it as a benchmark.

You're right, converting from mm to zoom is quite a waste of time.
As I understand, the longer the focus, the closer you get, and the x factor doesn't help me compare one lens with another.

Basically all I want to know is how close I get.
Minolta for ex has a 5.8 - 58.0 mm lens (35 mm equivalent: 38 - 380 mm)

As I understand the conversion, if I use a Canon DRebel, with a form factor of 1.6, compared to a regular 35mm camera, and use a telephoto zoom lens of 21-211mm as an example, I'll get on the canon DRebel a 1.6x(21-211mm) = 33.6-337.6mm equivalent, which is not bad but still less than Minolta.

Same lens put on a regular 35mm film camera will remain at 21-211mm.

Am I finally getting it? Basically: If I stand at 50meters of a brick wall and use 10 different cameras to take pictures of that wall, I will have on all the pictures the same number of bricks, as long as I use the same focal length.

[gerolamo]

Wouldn't it be simpler to just compare angle-of-view for this purpose?

I'm sure it's much simpler, but how do you find the angle of view? Is it in specifications? I'm looking right now at a canon lens showing Diagonal Angle of View 34° - 12° - is this it?

I get it, it's the the number of degrees the lens sees.
The smallest number has the greatest magnification.

[Andy_T]

Gerolamo,

there are also other telephoto lenses available.

E.g. the Sigma 50-500mm f/4.0-6.3 EX APO RF zoom is considered to be a decent lens (optical quality similar to the Canon 35-350L) that costs about 1000$.

On a 10D, it will give you 800 mm of reach ... this should be sufficient for most applications.

Best regards,
Andy

[Tom W]

Wouldn't it be simpler to just compare angle-of-view for this purpose?

I'm sure it's much simpler, but how do you find the angle of view? Is it in specifications? I'm looking right now at a canon lens showing Diagonal Angle of View 34° - 12° - is this it?

I get it, it's the the number of degrees the lens sees.
The smallest number has the greatest magnification.

That is it. But its not commonly specified, at least not on P&S cameras. For some reason, marketers have decided that the 35 mm equivalent is the 'de-facto' standard.

Unfortunately, I've seen several companies advertizing a 7-22 mm lens as a 35-105 mm lens. Unless they've changed the length of a millimeter, this is wrong and can lead to the false impression that the lens will act like its 35 mm counterpart in ways other than angle of view (like depth-of-field for example).

Don't worry, I'm not getting on you about it. Its just one of my pet rants (and as you read these pages, you'll find that I've got a few pets). ;)

[gerolamo]

Thanke guys, your comments were very helpful.

I know what to look for now.

I just hope I can find it :)