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Topic: Lenses for Elmo ST180
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Claus Harding
Phenomenal Film Handler
Posts: 1149
From: Washington DC
Registered: Oct 2006
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posted January 04, 2010 05:34 PM
Winbert,
Two things at work here:
The focal length (12.5mm-on up) of a projection lens determines the size of image you can get with it from a set distance. The F-stop (1.0-1.3) tells you the 'speed' of the lens, in terms of light 'efficiency'.
From the same projection distance, a lens with a maximum wide angle of 12.5mm will produce a bigger image than a lens with 15mm max. wide angle.
The F-stop (1.0 through 1.3) indicates the speed of the lens, as in: how bright the image will be on the screen. Given the same amount of light, a 1.1 produces a brighter image than a 1.3.
The Elmo 1.1 lens has both advantages: it is faster, for more light on the screen, and it is wider than the standard lens, for a bigger picture.
How big a picture do you need, and how far back can you go? If you tell me your screen width or the desired width of your image, I can tell you what the 1.1 lens needs in terms of floor space from the screen.
Claus.
-------------------- "Why are there shots of deserts in a scene that's supposed to take place in Belgium during the winter?" (Review of 'Battle of the Bulge'.)
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Winbert Hutahaean
Film God
Posts: 5468
From: Nouméa, New Caledonia
Registered: Jun 2003
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posted January 05, 2010 01:46 AM
quote: I am not saying it can't be done, but I have a feeling it's going to be neither cheap nor simple. Even among the enterprising bunch on the boards here, I haven't heard of anyone doing it.
Thanks Claus, but I can see the difference being live in a developing country (where everything is limited) and in a developed country, like Canada or USA. Here, everything is calculated (ruled) with safety regulations as well as high cost living. Please don't get offended with me. I lived in Indonesia, I lived in Fiji (poorer than Indonesia) and now I am in Canada (one of richest country).
In Indonesia, the engineers work with anything seen in their working area. Are those stuffs save? not necessarily, sometimes is dangerous.
So regarding the upgraded lamp, I have seen some one in Indonesia putting 250watt into Sankyo 700 and nothing wrong happened (at least as far as I know). But I saw they had an external transformer and also using domestic fan to cool the projector. Not a nice seen, but since this was used for outdoor screening for hundreds people....well it's OK (they supposed to use 16mm, but sometimes for short films they used 8mm)
So upgrading the lamp is more inexpensive in Indonesia rather than buying a lens (which obviously cannot be hand-made).
However, I can see your explanation.
BTW (OOT) being from a developing country, when I lived in a less developing country, I got an experience when my eyes were shocked having seen a car was filled with Coconut Oil!!. Well in the Pacific there are plenty of Coconut and sometime they didn't get fuel supply.
cheers,
-------------------- Winbert
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