Expert: Bill Edwards - 5/11/2009

Question
Hi Bill,

I don't know how to word this in a more sophisticated way - but how the heck do you differentiate one zoom lens from another? All the point and shoots just say "5x Optical Zoom" or "10x Optical Zoom." But now I have a DSLR and everything is broken down into MM. Can you explain how this works - and is there any way to convert, say, 50-200mm into "Optical Zoom?"

Thanks!
-Dave

Answer
Hi Dave,

Yes, lens choices can be confusing.  First of all 'optical' is preferred over 'digital' zoom because it actually makes the image enlarged using the optics in the lens vs. a digital zoom which basically just cuts out a big chunk of the image to make it appear closer - thus considerably less quality.

OK - now on to the "X Factor" . . .
A 50-200 zoom would be a 4x (50 into 200 = 4).  This 4x number only tells you what the lens zoom range is - the actual magnification from a normal lens perspective is different.

To get a 'normal' (not wide / not telephoto or magnified) a typical DSLR zoom should be set to 35mm on the zoom.  If you need to zoom in on something a 70mm zoom setting would give you 2x from normal.  A 200mm would give you 5.7x (35 into 200)  Get it?  (so this means your 50 - 200 is really 1.5 to 5.7x or slightly telephoto to telephoto.

Let's just talk about what good lenses to have in your bag are.  Number one - you can pretty much guarantee that you get what you pay for.  Get the best lens for your budget - it will pay off in Quality (sharpness and less distortion) and Brightness.  (right now I have a $2,000 zoom on my $900 Nikon D90)

But your question is more about zoom power.  I am a portrait photographer who actually shoots on an FX format Nikon D3 but for simplification let's keep this in typical terms of the more popular DX format camera which I am assuming you have. I would keep a 50 - 150 on a DX format camera almost always.  This is because I zoom in most of the time for close-ups of people.  When I need to get a group of people in a confined area I switch to a 15 - 50 mm zoom.  This way I can zoom way out and get everyone in.  

I also have an 18 - 200 mm zoom which I am able to keep on my D90 (which is DX format) for easy candid photographs since it goes from Wide to Telephoto all in one lens.  It's not as good as a quality as the two lens combination above but it costs almost $3200 less than buying both of those lenses.

Well, after you come out of the fog of confusion I laid on you - I hope this ends up helping.  

There is SO much more to learn about lenses that it's probably why there are books available on that subject alone.  The more you learn and experiment on your own the more all this will make sense.  I promise.  And after 30 years in the business I don't think for a moment that I know all there is to know either.

Good Luck.

Bill E