Telephoto lens

[nigels]

I have perhaps the most stupid question of the forum.

A telephoto lens of say 70mm-300mm. What actually is the zoom equivalent; would it be 4.5 that is 300/70 or more like 8 or 9.

Sorry for this most basic question, but my current E-20 has an additional zoom type of lense which is rated at 1.4, which finishes up at 5.8 considering the normal zoom capability 4X of the fixed lens

Nigel

[gstark]

Nigel,

I have perhaps the most stupid question of the forum.

A telephoto lens of say 70mm-300mm. What actually is the zoom equivalent; would it be 4.5 that is 300/70 or more like 8 or 9.

Sorry for this most basic question, but my current E-20 has an additional zoom type of lense which is rated at 1.4, which finishes up at 5.8 considering the normal zoom capability 4X of the fixed lens

Nigel

No, the stupid questions are the ones that remain unasked.

But what do you mean by "zoom equivalent"?

There's a zoom ratio, which is the expression of the zoom range of the lens in terms of the maximum to minimum focal lengeths - 300/70 = 4.28 (approximately).

Then there's the lens focal length equivalency when compared with how the same lens "sees" an image on a 35mm camera. That's taking into account the D70's 1.5 (approx) crop factor, and would be 105-450mm., when compared with the same lens mounted on a 35mm full frame camera.


There's been a couple of very useful threads on this and related topics recently. Have a look here and here for starters.

[mudder]

... my current E-20 has an additional zoom type of lense which is rated at 1.4, which finishes up at 5.8 considering the normal zoom capability 4X of the fixed lens

Nigel

G'day Nigel,
By "additional type of lense rated at 1.4" it sounds like you're referring to a tele-converter which simply multplies what-ever you've got by 1.4 once they're attached...

I had one on a Fuji S7000 I had recently... They don't zoom, they just multiply what-ever you currently are, so if your basic lens has a zoom factor of 4.3 (like with the 70-300mm zoom) then at max zoom it = 1.4 (your tele-conv) x 4.3 (the lens) = 6'ish

If it aint a tele-conv then I'm just waffling again...

Cheers,
Mudder

[nigels]

No mudder, you ae spot on correct, forgive my error

Nige

[mudder]

G'day Nigel,
Strewth, don't apologise matey... Don't ever be apprehensive about asking questions. It's great if one can help someone else, that's what it's all about on a forum like this... I'm just surprised that I could actually help!

It's all part of the fun

Cheers,
Mudder

[bago100]

I've been wondering about this zooming and lens range too.

How come you can buy really good fixed lens digital cameras with 10 times optical zoom, but to get a D70 with this magnitude of zoom, you would probably (and I'm guessing here folks) have to buy a 500 mm zoom lens at megadollars?

Maybe there is a fundamental difference between 10 time zoom digital cameras and a D70 zoom lens, that I'm completely missing?

Any enlightening discussion would be very welcome indeed.

Thanks

Graham

[MHD]

Because P&S cameras use optical components that are smaller than the smallest elements in our lenses...
using (true) FL's around 10-50 you dont need big glass to get good f numbers

It would be very easy to make a 28-500 lens cheap... but you would have to use f numbers like 11 to keep the price low...

cost is proportional to:
ABS(50-fl) + 1
1/f_number

[bago100]

Ah ha MHD

Now I am beginning to see why.

So the lower the F number, or the bigger the arpeture, the higher the cost to make lens that have a large zoom reach?

Thanks

Graham

[Glen]

Graham,
P&S are sold like stereos with mega watts to unsuspecting consumers. They like big numbers but it is all bullshit. The ratio they are expresing is minimum and maximum ie 100mm max with 25mm min means 4X. Well the widest lens I can stick on the D70 is 6mm and the longest is 1700mm that means 283 times zoom!!! They do this because they dont have interchangeable lenses, so it means something ie 25-100 is not as handy as 20-150 but what really matters is 35mm focal equivalent. P&S have small sensors and similarly small lenses. Focal length is relative to the sensor size (too long for me to explain here, have aread here http://www.kenrockwell.com/tech/2dig.htm ) So the real question is put there lens into 35mm equivalent and then compare, and yes it may be longer, shorter than the lens you have on your D70 now, but just unscrew that lens and put a different one on Try that with a P&S. Also those lenses arent fast so no lovely out of focus areas (boke) or action shots.

Ask away because this may have just confused

[Glen]

Graham you got it (while I was typing) that is why the 70 -300 4-5.6 goes for $250 here and the 80-200 2.8 goes for $2,000 here (it's superseded now)

[MHD]

and why the only fl you can get vfast lenses (1.8,1.4) is at 50mm

[MHD]

I mean cheaply

[gstark]

Graham,

So the lower the F number, or the bigger the arpeture, the higher the cost to make lens that have a large zoom reach?

Consider this aspect also: the bigger the glass - remember we're talking diameter - the larger the housing to mount the lens must be as well. So, it's bigger, and heavier, as well as carrying the heftier price tag.

[Paul]

Nigels, your not the only one confused by this question, I get it all the time from everyone with the old "how many megapixels and whats the x zoom on your camera" question.
I certainly understand now thanks to all the replies from our more learnered friends here!
Now to re-educate the masses.

[gstark]

Now to re-educate the masses.

Good luck with that, Paul.