Zoom ratio vs mm for lens specs

[stubbsy]

Thought I got this but I now know I don't

Here are some specs extracted from the Maxwell site for 3 lenses:
80-200 mm f/2.8 ED = 2.5x zoom
70-300 mm f/4 - 5.6 G = 4.3x zoom
24-120 mm f/3.5 - 5.6 VR = 5x zoom

I thought the larger the mm the bigger the zoom, but if that was the case the VR above would be just over half the zoom of the 200 but it's twice the zoom. And the 70-300 is a little less zoom than the 120 VR (and I'd have thought it was 2.5 times the zoom of the VR).

Is there a formula for working out the zoom ratio or do I need to look at specs for each lens (or am I focussing on the wrong thing - if you'll excuse the inadvertent pun)?

[as an aside I have the 70-300 and figured the 24-120 VR was of little use for zoom since the 70-300 covered it - needless to say, now I'm not so sure]

TIA

[sirhc55]

It’s a ratio:

200 divided by 80 is approx 2.5
300 divided by 70 is approx 4.3
120 divided by 24 is approx 5

Chris

[stubbsy]

Chris

Thanks

Embarassingly simple when you know.

So the zoom figure is a ratio between the two ends of the camera's focus range and doesn't tell me how close I can get to a subject (how big a subject can occupy in the frame from the same distance using different lenses). In fact that's what I should be using the mm for.

Or am I wrong yet again?

[skippy]

Kinda strange that Maxwell would post the 'zoom' figures, since I think this has come from the P&S world. The P&S cam-buyers like big numbers for the zoom, so the marketing depts oblige. My Fuji s5000 was proudly advertised as a 10x zoom, which was in actuality I think 5.7mm to 57mm. When you take into account the size of the sensor this became a 35mm equivalent of 37mm to 370mm.

When you move this to a real SLR camera it becomes pretty meaningless. As an example, two well known lenses on this forum are the 24-120VR and the 80-400VR. As a straight division they are both exactly 5x zoom. Equivalent lenses? Not even close. Ignore the 'zoom' number and go for the length you want.

[stubbsy]

skippy

Thanks that's what I was starting to think. So it's the length that really matters

[skippy]

Size, mate, size! The diameter also plays a part!

[stubbsy]

Maybe that's why there are so many men on this forum (sort of like having a red car!)

[christiand]

don't believe in the new age lens philosophy,
EVERYTHING matters.
(size, diameter, weight, lettering, design, shape ..., ..., ...)

[skippy]

Ah, the holistic approach...

[Deano]

And of course the beauty of a (D)SLR with interchangeable lenses is that it is the range of all of your lenses (assuming overlap) which defines your "X" zoom. I have 12-24, 24-120 and 70-300 so I get a 25x zoom

Cheers
Dean

[stubbsy]

Dean

I have 12-24, 24-120 and 70-300 so I get a 25x zoom

Yep that's where I'm at now. I have kit (18-70) + 70-300 and am lusting after 12-24 to achieve a simiular result now I have "the knowledge"

Cheers

[Greg B]

...............So the zoom figure is a ratio between the two ends of the camera's focus range.........

Not meaning to be pedantic stubbsy, but in the interests of getting it clear, it is focal length, not focus, in this context.

So, the zoom ratio is the ratio between the shortest and longest focal length of the lens.

(There will also be a minimum focus range, but that is another matter)

cheers

[stubbsy]

Greg. Nothing wrong with being pedantic. Clarity is important. Thanks

[Glen]

Stubbsy, I think it important that people realise a high zoom factor is not necassarily a good thing, in fact I personally would call it a bad thing (watch me get proven wrong in the next few years!). A few years back, Nikon pro zoom lenses had 2-3x xoom. eg 80-200 2.8 (2.5x), 35-70 2.8 (2x), etc. With increases in technology that has increased, but still absolute top line zooms, such as 200- 400, 70-200,28-70 2.8, 17-35 2.8 tend not to be high zoom factors. The reason for this is all lenses are a compromises and one lens cannot do everything well. There are now some great, what I would call maybe prosumer (not a perfect word, but trying to differentiate between a 200-400 versus 80-400) lenses such as the 80-400 which work extremely well (look at Gary's results!) which have higher zoom ratio's and are good. This is new technology at work. Then there are some really high zoom ratio lenses like the Tamron 28-300 (10.7 X) which in comparison to the lenses named above are POS. Then again everything is a compromise, and a station wagon isn't the best to be speeding up a tight winding road and a Ferrari isn't the best to bring home a dresser and king size bed in.

Hope this makes sense, but the gist of it is high zoom factors aren't always a good thing, because the higher the zoom the more compromises were made at one end or the other (or both).

[stubbsy]

Glen

Excellent analysis - makes perfect sense. Guess I'm showing how the marketing guys have conned this ex P & S person (don't get me started on megapixels )

[Glen]

Stubbsy, I too have been told the story about 8mp sensors looking through a lens smaller than a 1 cent piece and what unbelievable quality they are! Feel the megapixels. Glad you saw through it too!

Mate plenty of the guys here have forgotten more than I will ever learn about photography, I always like to bounce ideas or purchases off these wise heads. Look forward to meeting you on Saturday and your Christmas fruitcake