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April 10th, 2009, 12:18 PM | #76 |
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I could see where that might be true at the extreme ends of the spectrum, like when shooting day for night, but in the middle of the exposure range, when your iris and/or shutter speed would be adjusted to maintain the same overall levels, I doubt that would be the case. At the extreme upper end of the intensity spectrum -- i.e. everything blown out -- I would suspect that adding an ND would actually *increase* the contrast.
But as I said I haven't done a controlled experiment and put it on scopes. |
April 10th, 2009, 04:00 PM | #77 |
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It's also the reason lights are used when shooting in poor lighting situations. You can compensate by increasing exposure but it doesn't give the same oomph as adding additional lighting - thereby increasing the contrast and colour saturation.
A (very) simplistic illustration follows: If you take normal daylight on a cloudy day at, say, 10,000 lux (direct sunlight being approximately 100,000 lux - but this gets filtered to varying degrees as it travels through our atmosphere) then, if your subject includes an object which reflects no light (say black velvet) and an object which is pure white (reflecting the 10,000 lux) your total contrast will be 10,000 to 1. However, if you move indoors where the illumination is, say, 1000 lux - using your same objects - the black is still reflecting no light, but the white object is now only reflecting 1,000 lux (it can't still be reflecting 10,000 lux because there is no longer 10,000 lux available) so the contrast is now only 1,000 to 1 and the colours are less saturated as a result. However, the super circuitry in modern cameras tries to compensate for that, and to some extent succeed. If we really want to get the contrast back up and get better colour saturation and basically more overall "punch" we add artificial lighting to try to get back up to as near to daylight levels of illumination as we can. That's why professional outfits spend thousands on big lighting setups. If you're shooting in moonlight (typically 0.25 - 1 lux - we'll say 1 lux for the purposes of illustration) then your contrast is only 1 to 1 - which is why everything looks grey (assuming you have a sensor that works as low as 1 Lux). However, it is possible to artificially increase contrast in post (as well as what the camera tries to do) to some extent but the colour saturation still suffers to some degree and will never look as good as footage which has been optimally exposed in the first place. It's basically the same effect as decreasing exposure and increasing gain (ignoring the other elements that rear their ugly head due to the electronic nature of the light capture such as system noise) So, getting back to the original issue, if your daylight is stopped down from 10,000 lux to 5,000 lux through your ND1 filter, you have effectively reduced your contrast to 5,000 to 1 but the camera circuitry can compensate quite admirably for that by opening the iris more and/or adding gain to increase the exposure for the white object and artificially increasing contrast. However, as the light levels drop further, it gets increasingly difficult for the camera circuitry to compensate for the reducing contrast and the picture starts to look more and more "washed out" as it struggles to produce a true black and a true white. Last edited by Steve Renouf; April 10th, 2009 at 04:03 PM. Reason: spelling |
April 17th, 2009, 07:41 PM | #78 |
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Steve, I may be wrong, but isn't the typical dynamic range of the CMOS/electronics combination in cameras like the Z5, well below the kind of contrast ratios you're talking about?
I would think that white would be clipped significantly if you didn't use some form of ND filter or gain reduction. So, in effect, you would never really see or appreciate a greater contrast ratio if you avoided the use of ND filtration. But again, I may be wrong. |
April 19th, 2009, 06:57 AM | #79 | ||
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Quote:
Quote:
Steve |
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April 19th, 2009, 11:57 AM | #80 | |
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xlr's?
I think the z5 has xrlrs also
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April 19th, 2009, 12:40 PM | #81 | ||
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Quote:
It's pretty critical that all the filters (including clear glass) have not only exactly the same thickness, but the same coefficient of refraction. If they didn't the lens tracking would vary from filter to filter, and if "no ND" had no glass the tracking would be so different from the ND positions as to be unusable at wide angle fields of view. Quote:
The reason contrast range may seem to decrease with lower light levels is to do with directionality, and especially highlight/shadow ratios. Light a subject with a highly directional spotlight in an otherwise dark environment, and the contrast range of the subject may be just as high as in sunlight, even though the overall level is far lower. |
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May 25th, 2009, 06:25 AM | #82 |
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Yes Ed the Z5 has XLRs, but the original thread was about FX1000s. Additionally, the Z5 costs significantly more than the FX1000 and the Panasonic, obviously.
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