800mm OM lens calculates to what mm on Olympus Four-Thirds

Discussion in 'Beyond the Basics' started by jon_k, Aug 7, 2007.

  1. jon_k

    jon_k TPF Noob!

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    I'm looking for a good telephoto lens and I found an 800mm OM lens which is for 35mm. What would the mm conversion be over to an Olympus Four-Thirds system?

    (Basically 800mm in 35mm format = what in four-thirds format?)

    I just don't want to buy an 800mm OM lens and only get 120mm on my digital camera. I've got lenses that can do this. I'm not up on all the math involved so if somebody could point me in the right direction.
     
  2. Garbz

    Garbz No longer a newbie, moving up!

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    800mm in 35mm format? it would go up on a smaller format
    4:3 is 4"x3" = 18x13.5mm and thus a 2x crop factor.

    While for whatever reason I feel it's not right, it seems like it will be 1600mm
     
  3. Hertz van Rental

    Hertz van Rental TPF Noob!

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    I think the factor is about 1.6 - so 800 x 1.6 is around 1200 or 1300mm
     
  4. No Hertz, the crop factor on the 4/3rd format is 2:1. It's a great sensor, but it's a little small.

    Your 800mm (35mm equiv.) becomes a 1600mm lens. That's pretty long... you may have a real hard time hand-holding that shot.
     
  5. Don Simon

    Don Simon TPF Noob!

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    Ah the old conversion factor again... remember that the focal length is the focal length... e.g. an 800mm lens is 800mm. Putting it on a dSLR will not cause it to become 120mm or any other focal length except 800mm. To put it another way: You have a Sigma 105mm. Say you found an old 105mm OM lens... stick it on your Olympus dSLR and it won't give you a different field of view from the Sigma on the same dSLR, because the focal length is still 105mm.

    To put it yet another way: If you could use the same 800mm lens on a medium format film camera, a 35mm film camera, a dSLR with a sensor 1.5x smaller than 35mm, and your Olympus with a sensor roughly 2x smaller than 35mm... the angle of view would be different in each case. Use any number of different 800mm lenses on your Olympus however and the angle of view will be the same.

    Sorry for being long-winded, just trying to emphasise the point that conversion factor or crop factor is just a way of understanding the different angle of view with a given focal length on different film/sensor sizes, specifically when comparing with the 35x24mm format which for some reason is still considered standard. Because your sensor is approx 2x smaller than that format, an 800mm lens on your Olympus can be considered "equivalent" to a 1600mm lens on a 35mm camera... by the same token, your 105mm lens would be comparable to a 210mm lens on a 35mm camera, your 14-45 to a 28-90, etc. Unless you've used an 800mm lens on your Olympus or a 1600mm lens on a 35mm camera, the conversion factor isn't really much use here for providing a point of reference... except that as Iron says it will be long. ;)
     
  6. Hertz van Rental

    Hertz van Rental TPF Noob!

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    The standard lens on the Olympus 4/3rds dSLR's is about 25mm. The standard for 35mm film is 50mm.
    (The 4/3rds chip is 13.5mm high as opposed to 24mm on film so the factor is actually about 1.8)
    Now whilst an 800mm lens will remain an 800mm lens, on a dSLR it will behave as if it has a much longer focal length. It will be the equivalent of a digital 1600mm.
    Or, to put it another way, an 800mm lens on a dSLR will behave like a 1600mm lens on a 35mm camera.
    So we are all saying the same thing - just in different ways ;)
     

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