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Jack Russell
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Location: Kolossi, Cyprus
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12-05-09, 10:34 PM
#1

Lens numbers

Ever wondered why your lens has two numbers?

An 'experienced' photographer asked me today why their 70-300 has the numbers 1: 4.5-5.6

I explained - the 1st figure f4.5 is the lowest aperture at 70mm and the f5.6 is the lowest light setting at 300mm. Conversely for lens with only one number for example my 24-70mm, the only number is 1:2.8, which means throughout the zoom the lowest light setting is a constant f2.8 throughout the entire zoom range of the lens.

It got me wondering if everyone else knew that?


     
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13-05-09, 12:11 AM
#2

Re: Lens numbers

Certainly did. Suprised he didn't ask then why it has a 70 and a 300.
Kit 1
Nikon D700
Nikon 28-70 f2.8 ED AF-S (The Beast)
Nikon 80-200mm f2.8
Tamron 24-135 SP
Nikon 300mm f4
Nikon 70-300mm VR
Sigma 18-50mm f2.8 (DX)
Nikon 28-105mm (great walkaround on D700!)
Lensbaby Composer
Nikon 20-35mm f2.8
Nikon SB800
Kit 2
Nikon D300
Nikon 20mm f2.8
Nikon 24mm f2.8
Nikon 28mm f2.8
Nikon 35mm f2
Nikon 50mm f1.4
Nikon 85mm f1.8
Micro-Nikon 60mm f2.8
Micro-Nikon 105mm f2.8
Tamron 28-75mm f2.8


     
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13-05-09, 12:37 AM
#3

Re: Lens numbers

I didn't at first, but worked it out after a while I think because it gives you the f number on the view finder - which helped me figure it out. (Can't check as the camera is not near me at present).
Kit 1
Nikon D300
Nikon 55-200mm VR
Kit 2
Nikon D40
Nikon 18-55mm
My Compact/P&S: Panasonic Lumix TZ7


     
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13-05-09, 12:53 AM
#4

Re: Lens numbers

I did know that but there was a time when I didn't.

You're explanation is nice and clear though Jack.
Kit 1
Canon 1D Mark 3
Canon EF 17-40mm f/4 L USM
Canon EF 24-105mm f/4 L IS USM
Canon EF 100-400mm f/4.5-5.6 L IS USM
Canon EF 50mm f/1.8 II
Kit 2
1D2 & 40D


     
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13-05-09, 07:41 PM
#5

Re: Lens numbers

No I never knew that But I do now!! lol Thanks Jack.
Kit 1
Nikon D40x
Nikon 18-55mm
Nikon 55-200mm
My Compact/P&S: Sony DSC-W70


     
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13-05-09, 10:21 PM
#6

Re: Lens numbers

The only thing I might add Jack is that the lowest f-stop represents the "most" or highest light you can let in. Lowest light would be like f22.
18mm Fujinon
35mm Fujinon
60mm Fujinon
18-55 Fujinon
55-200mm Fujinon
Other Kit
View my profile to see my other kit!
My Compact/P&S: Fuji X-E1


     
Bazza
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13-05-09, 11:19 PM
#7

Re: Lens numbers

Well knock me down with a feather, I thought the f number was the strength of swearing that was allowed when the picture was rubbish.

Bazza


     
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14-05-09, 08:54 PM
#8

Re: Lens numbers

Odd that a "pro" wouldnt know that considering the lens is such a pivitol peice of the kit!! LOL


     
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15-05-09, 05:15 PM
#9

Re: Lens numbers

I knew that, but you could have knocked me over with a feather when I found that my macro lens which is f2.8 actually isn't and the closer you are, it goes to lowest 4.5 iirc. Don't quote me on it - I'm hungover and tired, but I know you can't get to 2.8 if you're close to things.

xx
Kit 1
Nikon D800
Nikkor 50mm f1.4
Nikkor 24-70mm f2.8
Nikkor 105 mm f2.8 macro
Nikkor 70-200mm f2.8
Sigma 50-500mm F4-6.3 EX DG HSM
Sigma 150-500mm F5-6.3 APO DG OS HSM
Nikon 70-300mm AF f/4-5.6G
Nikon 50mm f1.8
Kit 2
Nikon D700
Other Kit
View my profile to see my other kit!
My Compact/P&S: Fuji finepix bridge


     
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