Zoom Lens question mm Vs Feet?

[LordSummerisle]

Hi, first off id just like to say hi and thanks to everyone in these canon dslr forums for helping me with my decision to get a 20d :) being a total noob in the slr world, this was a great place to come and get advice.

Now my question.

I am after a 200 to 400 range zoom lens, either 70-200mm f/2.8 L IS USM or the 100-400mm f/4.5-5.6 L IS USM for animals/sports, as i said before, i am totally new to the world of the interchangeable lens, so have a few things to clear up.

I understand the whole mm measurement of lenses, i.e., the larger the mm the greater the zoom but im not sure just how far those zooms go in real distance.

For example, how far from the camera would someone be standing if a 200mm lens had their head and shoulders filling the viewfinder on a 1.6 crop 20d, I wonder ther same with all sizes from 40mm to 400mm, is there some kind of secret photographers formula to find this out:wink: .

Thanks in advance, Paul

[condyk]

Paul

There will be a formula but for me it's a 'who cares' thing that I have never bothered to think about. All I know from practical experience is that for wildlife that's wild you more often than not need to be at least 400mm ... and significantly over if you have it. Sometimes, on safari say, you will welcome some zooming down to even 200mm or so, but mainly you're at the long end. A 70-200mm won't do it because you will lose too many opportunities, or end up with a semi-indistinct spec in the centre of losts of grass lots of the time. You may get some lucky once in a life time shots at 200mm (or even 100mm!!) but you will soon get frustrated relying on luck. I'd say the 100-400mm will give great satisfaction, while the 70-200mm IS would be great for close up sports.

[lomond]

I agree with Condyk.

Also have you had a look at the stickies in the lens section. Good info there;
eg http://photography-on-the.net/forum/showthread.php?t=59931

[LordSummerisle]

Thanks condyk and lomond,

I guess if i get the 100-400 I'll get the 200mm included in that range anyway, i just wont have the f/2.8,
I've always wondered similar things about primes, if you have a 400mm prime isn't it a lot more difficult to get the subject the right size and distance for a good shot, or is there something else im missing?

[condyk]

It's a debate ... and it all comes down to preference.

With a top prime, I am convinced you grab the last drop of image quality, but it's at the expense of framing ability. I prefer to flexibility of a quality zoom. A top zoom will lose little and you get the flexibility for free.

The 100-400mm IS is the top recommended wildlife zoom. I had a 400mm prime in South Africa and Namibia and, as you say, there was some difficulty with framing the critters as I wanted at times. Personally, I like to capture the look in the animal's eye, it's nature, rather than just a static image of it. The ability to fit in frame as you judge appropriate is essential.

[ron chappel]

This page has a neat little feature that allows you to determine exact focal length by entering several details.
Remember to mutiply for digital though!

[Michaelmjc]

Ron, what page?