Low-light sensitivity w/kit lens vs other cameras (i.e. HVX200, DVX100, etc.)

Tom Shortridge

Tom Shortridge

Well-known member
Dumb question.

So, like the topic title suggests, I'm wondering about low-light sensitivity of the kit lens. If I'm correct in my understanding, you can only open up to an f4.0 . What I'm curious about, is how does that f4.0 compare to the wide-open aperture on an HVX200 or DVX100, for example, with the different sensor sizes? Are they comparable, or is one more sensitive? (Let's say, for our purposes, we're using a standard ISO. For that matter, is there a "standard" ISO? I'm still trying to learn about DSLRs. Feel free to "noob" me.)

Thanks.
 
Sensor size doesn't have anything to do with sensitivity for this discussion. The "ISO" of the sensor is the ISO, so what you really want to compare is noise performance.

A DVX100 will slaughter a DSLR when it comes to sensitivity, because it has a 1280 base ISO (in 60i mode), and its lens will open up to f/1.6. The DSLR opens up to f/4, so to get equivalent brightness you'd need 2 2/3 stops more sensitivity, which means you'd have to put the DSLR at ISO 8000 at f/4 to get the same sensitivity as the DVX at 1280 ISO and f/1.6. But, I don't know noise-to-noise, if the DSLR would be noisier at 8000 ISO than the DVX would in 60i mode.
 
Barry,

I have the Gh1 now after trading in my DVX, and I think the Gh1 holds up with less noise in the dark better than the DVX, unless of course you're way underexposed and have banding. You also have to remind people that you can adapt the kit lens and use a 50 1.4 on the Gh1 and shoot at 400 ISO, maybe even 800 if you want, and get a real bright image. Shooting at 1.4 or even 2.0 on the Gh1 at 400 produces a pretty decent image without using any real lighting. I think the blacks are much cleaner on the GH1 than the DVX, when you don't run into banding issues.
 
Yeah the GH1's kit is pretty slow...that said because you lose light with 35mm adapters the GH1 will do better with other lenses than will the HVX, etc.
 
Yes, but again, not the question at hand. Once you start adding other lenses or 35mm adapters into the mix, you're dealing with an entirely different animal.
 
Sorry to muscle in on this topic, but it is related. What is the base ISO for a DVX100B in 24p mode? I know the response of the CCD's are not linear and that using a light meter isn't ideal with it, but just roughly speaking.
 
Thanks for the info, Barry. Any chance you could point me to a reference/table of how ISO/aperture/f-stops works mathematically?
 
aperture = f-stop.

If you double the ISO, you double the sensitivity. If you open up the iris by one stop, you let twice as much light in. If you cut the ISO in half, you cut the sensitivity in half. If you close the iris by 1 stop, you let half as much light in.

So ISO 400 @ f/2.8 will give the same brighness as ISO 800 at f/4.
 
Barry_Green said:
aperture = f-stop.

If you double the ISO, you double the sensitivity. If you open up the iris by one stop, you let twice as much light in. If you cut the ISO in half, you cut the sensitivity in half. If you close the iris by 1 stop, you let half as much light in.

So ISO 400 @ f/2.8 will give the same brighness as ISO 800 at f/4.
Click to expand...

Just adding to this, for those not familiar with it. One stop with regards to aperture/iris is a multiplier of 1.4x, hence 1 stop slower than 2.8 is 2.8 x 1.4 = 3.92 (rounds to F4).
 
Also don't forget about how shutter speed relates to all this (although not to the original question really) in that it effects how bright the image is...a slower shutter speed will let in more light and a faster will let in less...unless I'm mistaken this relationship is totally linear (IE 1/1000 shutter lets in 1/10 the light of a 1/100 shutter, which lets in 1/2 the light of a 1/50 shutter...)
 
Ben_B said:
Also don't forget about how shutter speed relates to all this (although not to the original question really) in that it effects how bright the image is...a slower shutter speed will let in more light and a faster will let in less...unless I'm mistaken this relationship is totally linear (IE 1/1000 shutter lets in 1/10 the light of a 1/100 shutter, which lets in 1/2 the light of a 1/50 shutter...)
Click to expand...

Indeed! Of course when you get into really long shutter speeds in still film photography you start bumping your head against reciprocity failure...but still technically the relationship is linear, and the kind of shutter speeds I'm talking about don't get used for video...maybe if you were doing time lapse, but still, strictly speaking in terms of exposure, the relationship is linear.
 
Barry_Green said:
Roughly speaking, over most of the exposure curve, it's 640 in progressive (24p/30p) and 1280 in interlaced (60i).
Click to expand...


This is an interesting thread

I started out in still photography (shooting on film) where the iso was determined by the film you loaded and was the same regardless of what camera you where using. 400 iso film had the same grain in my 1968 minolta as my dads 1989 minolta. so its always been hard to wrap my brain around DSLR with iso setting which are adjustable. surely the iso settings must be artificially created in the same way Gain is used in a Video camera? i mean its not like we change the sensor for a more sensitive one like we might film?

and if this is the case, would it not be far simpler to express a cameras sensitivity by some method which is an absolute like native sensor iso (no gain) especially as it relates to known standard like film iso which we can all relate to.

Though now that i think about it probably fewer and fewer people can relate to film iso's as the years roll on.

I have been looking for a good comparison of the gh1's low light capabilities for some time. I shoot mostly weddings and it kills me to see what sort of images my photographer friends come away with in low light settings (practically all the receptions we go to)

Mr. Green you seam to take an analytical and scientific approach that seeks to eliminate variables. I have also read your findings with enthusiasm. I have also read your comments of frustration at folks criticizing your methodology so please do not think that i am doing that. However, i think the OP's question strikes to the heart of the matter which I have been agonizing over myself.

which is this "How does this new toy/tool compare to what i am already using and can someone please put it in such a way that i can relate to something i have not seen."

If the native iso of the DVX100 is in the 600 range what would the native iso of the GH1 be?

i currently shoot with an HMC150 and limit my gain to 12 db. Often my images are bright enough (brighter than they where to the naked eye) but they are so noisy that any advantage i had shooting in HD is gone. It is so frustrating working your tail off to get good footage just to have it look like you shot it on a tuck stop security camera.

any insight?

And i know that other cameras might be better in low light but i cant deal with 12 min record times and the stuff i shoot is too important to risk an overheat.

That is a really long winded bump to the OP's question

thanks in advance
john
 
Well, that gets back to what I said back in post #2, which is "relative noise performance". That's the only real way to fairly compare them, because yes, gain can add brightness at the expense of increasing noise.

And yes, that's what the DSLRs appear to do, although the Canons do it kind of funkily because the progression of noise isn't linear. Going to a higher ISO should always mean getting noisier footage, but it'll actually take a step backwards in noise on certain steps (so ISO 125 is noisier than ISO 160, for example, but 200 is noisier than 160, and 250 is noisier than 200, and then it goes weird because 320 is cleaner than 250...).

So, anyway, yes, getting back to film, we always understood that faster stocks were grainier. The sensitivity was, indeed, the sensitivity -- but the grain performance was different.

In video, we have the ISO that the sensor is rated at, but there's always some amplification of the signal going on. There's always some "gain" being added. The manufacturer tweaks and tunes the system to get the best compromise of sensitivity vs. noise that they can. Then they give us the gain dial, so we can push it further.

The DSLRs don't have "gain", but they do have adjustable ISO, which is basically the same thing. The higher you push it (generally), the noisier the footage becomes, just like gain.

So what happens if you have a camera that's super-whisper-clean at 400 ISO, and one that's rated at 800 ISO but is a noisemaster? Couldn't you just put 6dB of gain on, and end up with an even cleaner picture than the 800 ISO cam? Yes, perhaps you could. So if you want to be able to truly, truly judge whether one is "more sensitive" than the other, then you'd have to find some way of qualitatively judging the amount of noise in the signal as well.

It's easy to slap a gray card in front of the camera and get a brightness reading off it. It's less easy to determine exactly how much noise is in a signal, and especially when different cameras give off different amounts of luma noise, chroma noise, and exhibit noise in different IRE portions of the signal. It's just not all that easy.

With that said, maybe I'll try to put the GH1 up against the HPX170 and run through the gamut of noise offered by the gain and see if I can figure out how they compare at relative noise levels.
 
Barry_Green said:
Well, that gets back to what I said back in post #2, which is "relative noise performance". That's the only real way to fairly compare them, because yes, gain can add brightness at the expense of increasing noise...............................With that said, maybe I'll try to put the GH1 up against the HPX170 and run through the gamut of noise offered by the gain and see if I can figure out how they compare at relative noise levels.
Click to expand...

Thanks for confirming my assumptions about Gain vs adjustable iso's

And altho i would love to see the gh1 vs something i can wrap my brain around like the HPX170 don't go doing that on my account.

What we need is a GH1 that goes up to 11.

It's just like a regular GH1 at 10 right but what if you need just that little bit extra, there is no where to go right. Thats where the GH11 comes in.

It's one more isn't it.

thanks
john
 
Ah, but such a thing does exist -- it's called springing for the f/1.2 lens. Or the f/1.0. Or hunting down the mythical f/0.7... :D
 
Barry_Green said:
Ah, but such a thing does exist -- it's called springing for the f/1.2 lens. Or the f/1.0. Or hunting down the mythical f/0.7... :D
Click to expand...

oh thats the other thing that I like about the GH1

I have a minolta 28mm f1.2, minolta 50mm f1.2, minolta 75-120 f2.8, and the monster 100-200 f4.6 just sitting on the shelf waiting to be put back into action. My dad bought them at the PX in Ramstien Germany 10 years before i was born (and paid an arm and a leg for them) and i think he would like the idea of me using them to make money almost 45 years later.

Wonderful glass that has been well taken care of.

Plus as much as i love my hmc150 i miss having real mechanical lenses that stop at the ends of travel. the iris rings give a very satisfying click-click-click. the lens caps are pressed aluminum. i just love that.
 
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