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08-06-2009, 08:21 PM   #16
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Yeah... i filmed some coy carp at night using only a flashlight and da70@2.4. Didn't think it would work, it did and was surprisingly noiseless.

A 1.2 lens would be great. I have a 1.4 but it is 'lent out' at the moment. Must get it back and have a play.

I don't believe you can set ISO for video mode manually can you?

mike

08-06-2009, 10:35 PM   #17
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I think you can..we will have to wait for confirmation on that...
08-07-2009, 08:53 AM   #18
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QuoteOriginally posted by Digitalis Quote
due to the light absorption of air, it's impossible to make a lens faster than f/0.5 and the adapters that he used to make that 50mm lens in to a 36.6mm lens actually made the lens slightly slower, not faster and it certainly didn't do wonders as far as it's handling of chromatic aberrations.. Kubrick actually push developed the film for the candle lit scenes to the best of my knowledge the fastest cine film available in the early to mid 1970s was about ISO 500 and he pushed it to ISO 1000 so, ISO 3200 with a 50mm f/1.2 works out to roughly the same exposure on a 50mm f/0.7 give or take a 1/3rd of a stop.
Nice. I didn't know that!

Though, I'm not convinced with f/0.5 being the fastest possible aperture. The F-number just expresses the ratio of focal lenth and pupil diameter. Unless air significantly affects the focal length, I don't see where it would fit in this equation. And even if it did you'd have to take into account air pressure and temperature then (which in turn would mean that in vacuum a faster aperture would actually be possible).

Anyway, getting off-topic
08-07-2009, 10:14 AM   #19
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I have used lenses from 15mm F2.8 to 2350mm F10 for HD video with my K-7 and it depends what my subject is as far a my favorite. For riding my mountain bike the 15mm F2.8 is what I use then for the moon it will be 1480mm F6.3 or 2350mm F10. For low light it would be 15mm F2.8, 50mm F1.4 or 85mm F1.4. For my last video I used a 28-300mm Tamron @300mm.
YouTube - Pentax K-7 (SR on) with 28-300mm Tamron @300mm of transmission line repair with helicopter ! part 3

08-07-2009, 06:21 PM   #20
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QuoteOriginally posted by amaurosis Quote
Nice. I didn't know that!

Though, I'm not convinced with f/0.5 being the fastest possible aperture. The F-number just expresses the ratio of focal lenth and pupil diameter.
sorry I should have said T-stops, air has it's own refraction index and there is always the Rayleigh light scattering properties of air to consider as well it isn't just oxygen we are breathing in there's a range of different gases in air... the refractive index is very small but it is there. And that is why multi coating lenses became such an important business. Because when light travelling through a material with a refractive index and hits another of different R.I - there is always a reflection where the two materials meet. If you go underwater and look at the surface of the water from underneath, that is the effect you are seeing. And that causes a major headache for lens manufactureres because they use glasses with many different grades of refraction.

yes, in a vacuum it is possible to make some really,really fast lenses.
08-08-2009, 04:41 AM   #21
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QuoteOriginally posted by Digitalis Quote
20mm f/1.4 lenses are a bit thin on the ground. Personally, I'll be using my 50mm f/1.2 for my video stuff...I could probably remake the candlelit scenes from Barry Lyndon with that lens.
And -thanks- for that nice article. I really enjoyed reading and didn't know that a F/0.7 even exists...
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