Setting light meter for HVX200a, what ISO/ASA?

[mrbrycel]

I plan on using a light meter with my HVX200a. I had read that the ASA/ISO is 500, but I also read somewhere else that setting the ISO on your light meter all depends on what mode your shooting in.

What should I know when setting a light meter for a 200a?

[Douglas Villalba]

In the video world the light meter is hardly used because you can see through a monitor what you are shooting. However is you are setting lights up before a shoot and want to have your ratios corrected before a shoot then you need a light meter.

I use 320 as reference with HVX 200 or 200 with the LEX. I think that it was Mr. Barry Green that said that the 200a was 500.

[mrbrycel]

Yeah, I've always used a Sony vx1000 (LCD-less), where the isolated viewfinder has always been accurate enough for me to get a good exposure by eye. But I know once my HVX comes, I'm going to pop out that LCD, and I know how dangerous it can be to trust what you see on it. I know zebra's are an option, but although can tell me exactly what is overexposed or exposed correctly, I'm not very clear on my contrast ratios. I'm used to shooting photos on 35mm, and am much more aware of the ratios by looking at the reading. And I figure that getting comfortable shooting with a light meter would probably help me in the future.

But yeah, I had read that 500 was the ISO, but I wasn't sure. But you and Barry said it again, so i'll go with 500. Thanks!

[atlfilmguy]

It is 500, until you get to lower light and lower f-stops. Look at Barry's book. The HVX200 is like ASA100 at f1.7.

The problem is that it is not a film camera, things will change depending on frame rate, codec, f-stop etc. The CCD is not a static piece of film, it is a dynamic electronic marvel.

You will notice that 500 for the 200A and 320 for the 200 are good in the mid f-stop range.
But be careful on either extreme.

Use a meter for ratios, but trust a PROPERLY set up monitor for exposure. Or use a waveform monitor.

[Jimmy Moss]

I just tested my 200a and I'm getting an ISO of 320 at HD Norm pretty consistently, which is actually kinda depressing because I bought it thinking it was ISO 500.

I think there was another post in the forum here where they e-mailed Panasonic tech support and they said the 200 and 200a were both ISO 320, but the 170 was ISO 500. It's only 1/2 to 2/3 stop difference but with a Redrock every stop counts.

Edit: I just tested with my redrock, HVX200a wide open/50mm nikon at f 5.6 and I got an ISO of 80. Looks like the redrock with a lens loses 2 stops of light.... ouch.

I'm doing the test by exposing an 18% gray card at 50% IRE for the given settings and then taking a reading with my light meter and changing the ISO (on the meter) until the F stop on the meter and lens match up.

So I'm guessing that a HPX170 at 500 ISO with a Letus which loses 1/2 stop? of light would put you at 320 ISO (might be 200 with a lens?). Which I think would be the highest ISO you could get with a 35mm adapter and Panasonic camera combination.

[Barry_Green]

The 200A should be delivering a 500 ISO in HD NORM. Be aware that the f-stop reading the camera reports can be as much as 1/3 stop "off" from a true reading, because the iris is calibrated in 1/6-stop increments but the readout only shows 1/2-stop displays. The difference from 320 up to 500 is only 1/2 stop, so 1/3 off could be within the margin of error.

Plus, video cameras perform less linearly when the iris is all the way open. You'll see a different "apparent" ISO at f/1.6 than you will at f/2.8->f/11.

The way I test it is to adjust the light to meet the camera's iris, not the other way around. Set the iris at exactly 5.6, by finely adjusting it so that it just barely crosses the threshold from 4.8 to 5.6. And by "barely" I mean BARELY. Then set the gray card up and get your reading, and move the light closer/further until you're getting 50 IRE. Then take a spot reading and you should get 500 on the spotmeter.

[Jimmy Moss]

Thanks for the reply Barry.

When I did my original test it was just with the camera itself at F5.6 and I did notice you could adjust the iris more than the 1/2 stop increments shown but your right, its hard to tell exactly which stop its on. I'll probably try again and see if I cant get it closer.

The only reason I ran the camera with the iris wide open and the redrock at f5.6 is because that is probably how I would be using it on a shoot indoors (trying to get all the light I can). Your right, the math wouldn't be right if F1.6 on the cam reports different ISO's than at f2.8-f11. I'll try it at f2.8 and see what I get. Thats probably the smart move on my part because the HVX is sharper a couple stops down from wide open anyway.

[berkanoztrak]

You have to remember that the f stop graduation on a video lens is "f" not "T" (transmition) as it is on cinema lenses. Your spotmeter gives a "T" value.
On lenses which have the two graduations there is 0.2 to 0.5 stop difference, for
"f" 1.8 the value of "T" may be 2.2 which is close of 1/2 stop.

[Jimmy Moss]

Is that general knowledge or does it depend on the light meter? I checked the manual and everything says F stop and it doesent mention it being a transmition value.

Edit: Im using a sekonic L-508 zoom master in Cine mode.

[Jimmy Moss]

Ok, so I've been racking by brain over this. I think I already hijacked this thread so I'll keep it going.

Here is what I am doing:

I set the HVX 200a to HD norm with a High Knee, everything at 0, I'm testing at 1080i 24PA with a 180 degree shutter angle, zoomed all the way out, and the iris at f5.6. My light meter in Cine mode assumes a 180 degree shutter angle, and I set it to 24fps. I light the gray card so that it just goes over 50IRE I then take a reading with the light meter, it shows 5.6 and 7/10th's of a stop when I set the ISO to 500. If I change the ISO on the meter to 320 it lines up at 5.6 and 1/10 of a stop. So thats about a half stop difference.

Now if the meter is showing me T stops and not F stops then you could assume the proper F stop would be 1/2 stops faster which would put me at f5.6?

So T5.6 7/10 = F5.6 1/10th?

Does that sound right?

[berkanoztrak]

"f" stop is a geometrical measure: the surface of the front lens divided by 2-4-8-16-... on the lens it shows 2 - 2.8 - 4 -... That number is the one to use in the calculation of the depth of field.
"T" (transmition) is the amount of light that will go through the lens, it also have the marks 2 - 2.8-... because when the iris is closed it cut the incoming light by 2-4-8-...
"T", shuter angel and frame rate give the "exposition" the amount of light that hit the ccd or film. And according to the sensibility of the film or ccd you are over/under exposed or just!
"f" shows how the stream of light entering the lens is halved, "T" shows the amount of light getting out of the objectif. Lightmeters refer to "T" because they are constant, what ever objectif. But still cameras lenses, video camera lenses are in "f" mode; cinema lenses are in "T" mode and of course the new generation of Digiprime or HD cine lens.
Jimmy your test and thinking are just . I asume you lighted the gray card with "Tungsten" light and you took a reading in reflective mode. I do not want to confuse you with all thieses " , but be aware that films emulsions and ccd are different. In tungsten light they are close and a reading with a light meter will give a possible exposition, in day light you are out.
I am sorry i am long or too short, but feel free to pm. ı will help if i can. Best, Colin.

[berkanoztrak]

I have the HVX200, zoom to 15mm, focus out to MF85, a gray card 18 % in tungsten light.
I put the diaphragm to 4 by turning the manual dial from 3.4 till it shows 4
I have the Marker on and i adjust the lightning to read 50% (like Transmition)
My dual master L-558 (sekonik) reads in incident mode:2.8-7 which gives a 250 ASA sensibility. In reflective mode, the same as Marker reading, i have: 4 -4or5 wich gives a close 200 ASA.
The fact that incident reading and reflective one are different is normal, i cannot put he meter in the very place of the camera. Then, how fresh is that gray card? the reflectance changes with the time. 1/4 ,1/3 stop difference is not a problem with negative emulsions. And lightmeter have been built for film emulsions.
But it is one point. Second: is my meter calibrated? That too shift with the time. I am sure whith your meter you will find something different. No measure is absolute! And in our every day jobs we do not need it.
Your camera is the important point, the Marker, Zebras and a Vectroscope help you to adjust to the best your diaphragme. A meter may help you to adjust your fill light according to the key ligth, but will not give informations in the extreme part of the image: low (black) high (when the white clips). Color correction in post solve a lot of problems!
And several cameras means sevral other problems!
Again long, best, Colin.