HPX250: HPX250 sensitivity comparable to HMC150

T

Terry_Martin

Active member
This is just to confirm the HPX250 sensitivity is roughly similar to the HMC150 and Cannon XHA1. I tested with a grey card evenly lit with two Cool Lights LED600 (5600K lights, with cam daylight balance), and measured the required f stop to bring the grey card to 100% on the waveform monitor (and Small HD DP6 in false color mode). The HMC150 was technically the most sensitive, with the HPX250 and XH A1 following at about 1/3 f stop lower. The HMC40 of course was about 2 f stops lower given some uncertainty in its gain structure.
So there is no surprise in the inherent chip sensitivity, and nothing to compromise the gains in pixel resolution and codec.
 
At 0dB the HPX250 isn't quite as sensitive as the HMC150; it's about 320 ISO whereas the HMC150 is about 500 ISO. But Panasonic did a funny thing here; they basically moved the concept of zero. There's no negative gain in the HPX250, so what would have been negative gain on an HPX370, is actually zero dB on the HPX250. And then they added high gain on the top end, higher than what the HPX370 has. So even though it's the same chipset, the HPX250 delivers a noticeably cleaner images, but does so at a lower ISO. If you put the HPX250 at 6dB, it's basically exactly the same as an HPX370. So they've permanently made it cleaner by starting it at a lower ISO, and then they added in higher gain so you can get it just as bright as a 370. Which all ends up working very well indeed.
 
There is a big difference in sensitivity depending upon which PAP noise reduction filter setting is used. like a stop and a half, and a resulting difference in SN.
 
Barry, would you say this sensitivity difference to the HMC-150 is about the same for the AC160?
 
Yes, the AC160 is about 320 ISO, so about a half stop less sensitive than the HMC150. But that's not the whole story. I mean, a standard-def DVX100 in interlaced mode is well over a stop more sensitive than the HMC150, but the HMC150 just kills the DVX in low light because of the difference in noise. you can easily gain up an HMC150 to about 9dB, overcome all the sensitivity difference, and still have less noise on an HMC150 than you'd have on the DVX. So the only way to fairly compare a 150 against a 160/250 would be to compare them on a noise-adjusted basis (i.e., where each is gained up to the point where they're viewed to be equally sensitive, does one have a noise advantage over the other?)

Also, the HPX250 has the ability to use the P.A.P. Type 1 filter. That doubles its sensitivity to about ISO 640. It's pretty effective, but it can also lead to some motion artifacting (streaking during fast moves, or the little micro-jello that people were complaining about on the HPX370). So that's a secret weapon that the HPX250 has, that the 160 doesn't. But still, yeah, you'd have to compare them on a noise-to-noise basis to know which one has the actually superior low light performance. I mean, the HMC150 goes to a maximum of 18dB of gain, but the 250 & 160 go to 30dB(!) That's way brighter, but is it noisier than an HMC150 at 18? I don't know, I haven't tried that test...
 
I am curious which full HD 10 bit 4.2.2 cam today is the most sensitive/night shot capable of them all? I don´t count AVCHD as comparable yet...
Aren´t the Sony´s still on top?
 
timbook2 said:
I am curious which full HD 10 bit 4.2.2 cam today is the most sensitive/night shot capable of them all? I don´t count AVCHD as comparable yet...
Aren´t the Sony´s still on top?
Click to expand...
Sony doesn't have any full HD 10-bit 4:2:2 cameras. Panasonic's the only one with a 10-bit codec. Well, maybe if you count HDCAM-SR, but... for affordable units under ... what, $50,000... Panasonic's the only one making 10-bit camcorders in that price bracket. The HPX250 is the only handheld 10-bit video camcorder in the world. So by default, an HPX250 with P.A.P. 1 would be the most sensitive/night-shot capable cam of them all...
 
As a part-time event videographer, low light is key for me. I already have the HMC150 and was hoping to partner it up with an AC160/130. I'd really love to see some low light comparisons between the two cams and I'm a little bit disappointed that the 160 doesn't "blow away" the 150 in low light. Or does it?
 
Can I turn PAP off ? I can see I can switch between PAP 1 and 2 but there doesnt seem an option to turn it off ???
 
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