600mm f2.8 lens size...

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rogs
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Joined: Jun 16 2006
Apologies if the answer to this is obvious - I'm afraid my physics is not very good!...
 
I have always understood that a 600mm f2.8 lens would normally be almost large enough to have it's own post code!
 
So how is this possible?....
 
Or is it just marketing 'hype' ?.... Bit naughty if it is!
 
If it is true ... what are the limitations, as against a full size 'monster' 600mm lens?.. 
 
 
 
 
Dave Jervis
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Joined: Feb 21 2006
Re: 600mm f2.8 lens size...
Is that focal length an "equivalent focal length for full frame 35mm camera"?
 
That seems to be a popular way of representing lens angles in a world where sensor sizes vary....
 
( I would prefer horizontal angle in degrees, but that might not suit everyone...)
sleepytom
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Joined: Sep 15 2000
Re: 600mm f2.8 lens size...
i believe it is 35mm equivalent - which means its actually 300mm (MFT has 2x crop) so thats the biggest part of the question answered; it's smaller because it is not a 35mm lens. 
 
It should be a great video lens - no ramping with such a long zoom is impressive. If only they would build such a lens into a proper video camera.

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PaulD
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Joined: Aug 31 2002
Re: 600mm f2.8 lens size...
This is what the Specifications page says:
Focal Length f = 4.5 - 108 mm (25 - 600 mm in 35 mm equiv.)
(28 - 672 mm in 35 mm equiv. in video recording)
tom hardwick
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Joined: Apr 8 1999
Re: 600mm f2.8 lens size...
As Paul says, it's a 28 - 672 mm f/2.8 equivalent in the video recording mode because of the 16:9 aspect ratio masking out some of the 1/2.3'' chip's surface area.  But it's as well to remember that it's still only an 108 mm f/2.8 lens at maximum telephoto, so differential focus will have to be actively sought after.
 
tom.
Dave Jervis
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Joined: Feb 21 2006
Re: 600mm f2.8 lens size...
A quick look at the spec. also reveals the following....
 
" F2.8 / Multistage Iris Diaphragm (F2.8 - 8 (W, T)) "
 
...which makes me wonder what is meant by " Full Range F2.8 " in the headline features list.
rogs
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Joined: Jun 16 2006
Re: 600mm f2.8 lens size...
Thanks for the responses - they certainly pointed me in the right direction to read a bit more, and perhaps improve my physics! Thanks again.
 
I can see that, with so many different 'non 35mm' sensor sizes, it makes sense to have a common reference point.  But if you don't realise what they're saying (or simply missed it - like I did) it makes the size problem seem a bit odd.
At least it makes sense, unlike some 'hijacked' technical terms!   
 
In the audio world for example, manufacturers have been quoting 'RMS Watts' for years.  
There's no such animal!   A Watt is a Watt  - work done at the rate of one joule a second
There's no 'RMS watts - 'peak power watts' - 'music power watts' or any other kind of 'specified' Watt.
But that doesn't stop you finding these terms all over the place!
tom hardwick
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Joined: Apr 8 1999
Re: 600mm f2.8 lens size...
Dave, that f/2.8 to f/8 means (to me) that the lens has only those three stops to play with, regardless of the focal length selected.  All the rest of the exposure changes are accomplished using internal ND filters and variable shutter speeds.
MAGLINK
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Joined: Mar 8 2007
Re: 600mm f2.8 lens size...
and by the W and T I would take this to be an f2.8 lens at the wide end and f8 at the tele end which makes comparisons pointless as the large old school SLR lenses tend to be 600mm and f2.8 etc.
 
Medidox
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Joined: Jun 20 2005
Re: 600mm f2.8 lens size...
Gary Nattrass wrote:
and by the W and T I would take this to be an f2.8 lens at the wide end and f8 at the tele end which makes comparisons pointless as the large old school SLR lenses tend to be 600mm and f2.8 etc.
 
The marketing blurb says f2.8 at 600mm (equivalent) so I don't think the lens is ramping down as you suggest.
MAGLINK
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Joined: Mar 8 2007
Re: 600mm f2.8 lens size...
Ok I stand corrected I just thought like a lot of other stills lenses that the apperture changed as you zoomed.
Dave Jervis
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Joined: Feb 21 2006
Re: 600mm f2.8 lens size...
Ahh, got it, thanks Tom and Medidox....
It finally clicked for me when I saw it next to the fz150 spec. which is:    F2.8 - 8 (W)  F5.6 - 8 (T) 
dave