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Old September 5th, 2005, 03:09 AM   #1
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Sensitivity specs

For years i'm used to checking the sens specs on pro cameras with interchangable lenses (ex. F8 at 2000 lux). This numbers makes sense, as they allow us to compare low light performance of cameras.
1/3" camera manufactures don't publish these spex, i guess because these cams use fixed lenses.
The HD100 uses professional lens, so this measurement is possible. Giving numbers such as 3 lux without reference to aperture is useless for comparison.
These days most consumer elecrtronics companies
downgrade or completely ommit specifications. ( Would you buy an audio amplifier without a full page of specs?)
We are pros and we need every single number that will help us make a decision.
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Old September 5th, 2005, 03:32 AM   #2
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They do publish that spec. JVC claims 2000 lux at F8 for the HD100. Don't know if they said whether that was with gain or not though...

Whether it's a fixed lens or not doesn't change anything. Panasonic publishes a figure of f/11 at 2000 lux for the DVX, and that camera uses a fixed lens.

Even so, you still can't accurately judge low-light performance, because that doesn't include the effect of noise. The DVX is at least a full two stops faster than the Z1, for example, but the Z1 is quite noise-free in its low-light performance, something the DVX isn't. Even with some gain on, the Z1 is still quite clean. The HD100's gain is noisy noisy noisy. So low-light performance depends on your level of acceptance of grain/noise too. If you don't like noise, then on a DVX or HD100 you can pretty much rule out using any gain, whereas with a Z1 that's not necessarily true.
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Old September 5th, 2005, 10:08 PM   #3
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Don't forget that the more you zoom with a Z1 the less avaliable apature you have so you effectively loose a full stop of sensitivity at full zoom, where as you don't with the HD100.

By the way:

In http://www.gyhduser.com/showthread.php?t=98 I wrote:

30) Sensitivity at 24p 1/48th second -- no gain -- is 2000lux at F8.

31) Sensitivity at 30p 1/60th second -- no gain -- is 2500lux at F8.

So for me, working at 1/50th second I will be closer to the 2000lux at F8.

In comparison the 1/3" DV300 is F11/2000lux
In comparison the 1/2" DV500 is F11/2000lux
In comparison the 1/2" DV5000/5100 is F13/2000lux
*Taken from NTSC models specs (I assume 60i)

F8 is one full stop slower than F11 and about 1.4 stops slower than F13.

2500lux is 25% more light than 2000lux (2000 is 20% less than 2500)

Does this mean at 1/60th, you have about 2000lux at f7

F7 is 1.3 stop slower than F11 and about 1.7 stops slower than F13.

So in a worst case senario the HD100 is almost 2 stops slower than the 5100. That is pretty nasty for special events work (I hope the gain is really clean).

I can't find any specs on the Z1 in the same rating schemes (only the max gain 3lux rubbish etc).
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Old September 5th, 2005, 11:30 PM   #4
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F8 at 2000lux sounds good - a 50w light might be necessary- i use cams with this sensitivity for 10 years with good results.
However, i can't find any info about this on JVC site.
Also, i own a GY-DV5100 and there is no mention on sensitivity in the users manual specifications.
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Old September 6th, 2005, 12:19 AM   #5
Barry Wan Kenobi
 
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Quote:
Originally Posted by Guy Barwood
So in a worst case senario the HD100 is almost 2 stops slower than the 5100.
Haven't had an opportunity to do a side-by-side comparison. But two stops slower than a 1/2" camera sounds about right. It also sounds about a stop faster than the Z1, but again, we'd have to do side-by-sides to verify.

Quote:
That is pretty nasty for special events work (I hope the gain is really clean).
Nasty? I don't know about that. You cannot expect similar sensitivity when you're dealing with such tiny pixels -- it's a physical impossibility. If it's actually only a stop slower than the DVX, I think that'd be darned impressive. Now, whether that's appropriate for event work remains to be seen, but if they're able to put 3x as many pixels on a chip and only lose one stop... that's quite an accomplishment.

All these HD cameras are going to be slower/less sensitive than their SD counterparts -- that's unavoidable. Especially if you're comparing a 1/3" HD camera against a 1/2" SD camera.

But to dash your hopes, the gain isn't "really clean", it's instead quite noisy -- at least as compared to the Z1. Then again, the Z1's gain is unusually clean.
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Old September 6th, 2005, 01:19 AM   #6
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That was actually writen before anyone had got their hands on one, I'm happy with the gain up to 9dB but past that it is like most JVCs I've seen :(

With my DV500 if I set it to 6dB in a reception my 50W light does really well, but with a HD100 I'm going to have to use either more light power (draining battery faster) or more gain. Neither are desirables but I'll survive.
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Old September 6th, 2005, 05:23 AM   #7
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Quote:
Originally Posted by Barry Green
But to dash your hopes, the gain isn't "really clean", it's instead quite noisy -- at least as compared to the Z1. Then again, the Z1's gain is unusually clean.
There you have the advantages of higher compression: the higher pixel-count per second (interlaced doesn't matter in this case), makes the compression om 25 Mb/s of the sony *a lot* more then the JVC's 19.7 Mb/s. Such high compression tends too "smoothen the image". something you normally wouldn't like, but in case of having too use gain - and be honest, who likes it? No one does, we just have to, because the camcorders are NEVER sensitive enough - it is actually an advantage...
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