View Full Version : Comparing Stops of different cams?
04-04-2008, 05:29 PM
I am trying to understand when someone says a CAMERA 1 video cam has 2 more stops than CAMERA 2. Can someone help me understand what this means?
My understanding is that if CAMERA 1 and CAMERA 2 were both set with the same shutter speed, and aperture/iris opening, that CAMERA 1 would be able to take in more light? Again for the same settings.
If this is true, then by opening the CAMERA 2's aperture 2 more stops you'd get the same exposure and the scene would be lit similarly thru both cams? Is that accurate? One more questions. If this is true, the downside of opening CAMERA 2 would be that the depth of field would not be as shallow...in other words CAMERA 2's background would not be as blurred as CAMERA 1? Is this true 2?
Lastly, in a dark scene with high action, it would seem CAMERA 1 would be best and if the background blur is important (depth of field), CAMERA 2 could not do everything CAMERA 1 could in challenging situations?
IF someone can let me know if I have this right I'd really appreciate it. Thanks so much-
04-04-2008, 07:20 PM
I am trying to understand when someone says a CAMERA 1 video cam has 2 more stops than CAMERA 2.
A scene has a range of brightness. Let's say that you wish to have a shot of an actor standing under the shade of a tree, while another actor walks past him in direct sunlight -- this is all in a single wide shot. Suppose the actor under the tree is wearing a black suit, and the actor walking by is wearing a white suit.
The amount of light bouncing off of the black suit is maybe 10 lux, while the white suit is 10,000 lux. That's a difference of about 10 F-stops.
If you used an old video camera, you have to make a choice about exposure, because it has a range of about 5-7 F-stops. If you close down the aperture enough to see texture in the white suit, then the black suit will have no texture. It will look like a flat black rectangle. And the other way around: If you expose for the black suit, then there will this glowing angel going down the street.
A camera with "more stops," however, may be able to capture texture in both the white suit and the black.
04-04-2008, 07:31 PM
So with that definition is that the same as dynamic range?
Also are all cameras rated for how many f-stops they can capture in one scene?
04-04-2008, 07:43 PM
the same as dynamic range?
are all cameras rated
No. In fact, most aren't.
04-04-2008, 08:16 PM
If this is true, the downside of opening CAMERA 2 would be that the depth of field would not be as shallow
On rereading that I think you have it backwards. Opening a camera's aperture results in less DOF, or more out of focus background.
Regardless - you can use a Neutral Density filter on faster camera to artificially darken the scene so a wider aperture can be used any time you want. (to get shallower DOF)
So the advantage lies with the faster camera normally. When I say faster I really mean, when the aperture of both cameras is as wide open as they both get which camera lets in more light. (I'm assuming video cameras here and not RED) Some cameras have wider max apertures than others. Often this gets glossed over in tests.
A lot goes into comparing cameras actually and the little side by side tests people post don't really cover all the things I personally want to know.
04-05-2008, 04:37 AM
What would you guess the dynamic range (how many stops) my Sony Z1u would cover?
What about my single CMOS chip Sony HC1 and HC7? I do notice my friends Canon HV20 does quite a bit better...the blacks are deep and fairly rich compare to my Sony cams. And it covers the bright stuff pretty well too all in the same shot...again to some degree...nothing like a pro cam though I am sure.
I for sure notice the lack of detail in blacks or the "blown" out over exposed shots in sun due to the so-so dynamic range I believe...I imagine the Red's range would be far greater in stops?
I shoot rock shows with very bright lights and lots of dark spots...my cams just don't do it justice. Was wondering what would be best.
I see a lot of pro's use the expensive Sony cams like the F900 or F950. But I am not going to drop $100K on a cam.