New GS400 Owner ... ISO & Light meter for video?
 

G'day all

I just bought my new GS400, very happy I did given the prices coming down with the announcement of the GS500? ... even moreso given that the early reports of the GS500 are pretty shocking; seems I bought at a perfect time!

My question ... I have a Sekonic L358 Light Meter that I use for my still photography and it has many great modes including Cine which allows you to set FP ... such as 25 fps. I am very interested in calibrating the general ISO of the GS400 for the Sekonic because I can take all kinds of average metering in both reflective and incidental and I imagine use it with the GS400 to get better control over my lighting.

One thing that confuses me ... I have the PAL version, I have read that the PAL version runs at 25 fps and the NTSC is at 30 fps, right? Are these frame rates only in the Frame Pro Cinema mode but not in 16:9 and 4:3? I have understood that the latter two modes are in 60i or something ... can someone explain what 60i is in comparison to the Frame rate of 25 fps?

Ok, the reason I ask also is because I can set the Light Meter for 25 Fps but then it gets tricky because I'm not sure how I am to be calculating the general ISO of the GS400? Now in the 16:9 and 4:3 I guess I can ( I would use normal metering and not Cine 25fps ) just aim the camera at a grey card or white card and find out what the shutter speed and iris shows and then just calibrate the Light Meter until it shows same .... right?

Sorry for the longwinded post, but I have less than three weeks to get my head around the camera before I'm shooting an independant Doco overseas!

Apreciate all the help I can get!

Best, Simon.

Hi Simon,

I assume that you intend to use video function instead of still photo function of gs400 in your post. Am I right?

Regards
Leigh

Leigh ... yes ... I am totally talking about the Video features here and not the digital still features.

Hi Simon,

I don't think film ISO apply here. I am happy someone else correct me if I am wrong.

Regards
Leigh

Hey Leigh,

Well I have read others at the Pana CCD forum mention some ISO guestimates for the GS400 but nothing solid ... I was wondering if you could clear up my question regarding the Modes and 25 fps vs 60i etc?

Does the PAL GS400 shoot at 25 fps in every film mode or only in Pro Cine while the other modes are in 60i? What is the difference between the 25 fps and 60i?

Thanks! Simon

Hi Simon,

I bought a NTSC version of GS400 which is nv-gs400.

I don't know anything about PAL version. I only know for NTSC the frame rate is 29.97 fps for two frames combined together. It arounds to 60

Sorry about that.

Regards
Leigh

Hey Leigh ...

Well I did it myself and actually found data elsewhere ... Guy Brunner seems to state that Panasonic give the GS400 an ISO of 100 at 1/60 ... this actually pans out because I did a calibration test outdoors against a white card and got an ISO of 50 at 1/50 and f16 ... ISO 100 and ISO 50 in still photography are 1 stop apart.

Hi Simon,

Good work.

Would you please tell me how you test to get iso number?

TIA

Regards
Leigh

PAL will give you 50i (50 fields per second) or in frame mode 25p (25 fps).

NTSC is 60i and 30p respectively.

You can either select pro cinema mode which switches to 16:9 and 30/25 fps, adjusts the gamma curve, and selects bass enhance automatically.

Or, you can select frame mode (30/25 fps) with either 4:3 or 16:9 (e.g. not using the pro cinema mode).

Unfortunately, it doesn't allow the gamma changes with interlaced footage.

You need to see what you prefer but I'm not a great fan of the 25/30p modes.

For example, mine is PAL and frame mode shoots 25p. What is actually does is shoot at 1/50th still (I read that it shoots two fields very very close together and puts them together as one frame). This means there is a big gap before the next picture is taken. This results in jerky movement

50i produces a field every 1/25th so produces much smoother movement.

Time to experiment and see what you like.

Jason

Hey Leigh ..

Actually I was a little off but within 1 stop of correct! The reason for this is that the GS400 has internal ND filter control, so when I was outside the Cam closed down to f16 at 1/50th using the internal ND's so the initial reading I got was less than it should have been. I got a reading of 50 ISO but apparently Pansonic ( as it turns out ) give the Cam an ISO of 100.

Ok, the real world ISO of the GS400 turns out to be more like ISO 80. Here's what I did. I got the GS400 and aimed at a scene - you can use a grey card or a white card also ... I found this worked just as well by just aiming it openly. So set the exposure to Auto and arrange the light so you get the Iris to read around f1.6 or f2 at 1/50th. The general idea is that when the iris is open the ND's are not engaged and so you get a true reading without compensation from the GS400.

Right ... after exposing the scene in Auto, switch to manual and hit the Iris/shutter button twice so that it shows the F stop and Shutter reading. Once you do this you can do one of two things. You can use the metered reading from a still camera or do what I did and use a dedicated light meter. Using either one of the above, aim them in the same direction as the cam, preferably from the exact position of the GS400 lens and take a reading with the shutter value set for priority at 1/50th. The F stop will show as something now while the shutter speed is fixed as above. Using my light meter I just adjusted the ISO until I got the exact same F stop value at 1/50th on the GS400 which is generally about ISO 80 or thereabouts.

Initially the cam gave me ISO 50 which is a 1 stop difference which also shows that the ND at f16 that works internally with the GS400 is roughly a 1 stop or 0.3 ND value.

Et voila .... silly that I ended up answering my own question but there ya go. :)

Hey Jason,

Thanks for chiming in mate ... funny how these things go around. A guy at another forum ( very knowledgable ) was recommending I shoot in Pro Cinema mode to get the more filmic look for my Island Travel doco ... I was under the impression that the gap you are talking about mimics the gap of the pull down in film frame rate ... even though they are still different creatures and the end result projection speed of film is faster or something when it comes to movie time anyway.

I suppose I will need to find out allot more about the characteristics of Pro Cinema Frame mode also ... I hear that the dynamics of Pro Cinema leave allot more to be dsired in terms of the overall latitude and the gamma curve in regard to highlights and shadow detail with only a slight loss in saturation. I guess the only downside is the apparent choppy frame movement, yes? Have your tried cranking the shutter speed up a bit or is this not possible in Pro Cine?

Hi Simon,

Thank you very much.

I don't have a still camera nor a light meter.

So I can't do the same test as you did. Sad.

Regards
Leigh

Film is 1/24th so it's open longer. Any movement gets blurred. The GS is only for 1/50th so there is less blur - and a bigger gap between the next image. It's doing 25fps in the same way 50i is doing 25fps - just the frame mode is leaving a bigger gap between the fields than 50i.

You can crank the shutter up but that just creates more stuttery movement. In fact, you can get some great Matrix style effects at very high speeds.

And, as you say, the film frames are projected repeatedly to stop the flicker.
But, I think it's the blur that makes film acceptable.

Now, if we had a progressive CCD that could capture a whole frame at 25fps then that would go a long way.

Still, I'd rather have 50fps than 24. 24 was only used because it was the minimum the film industry could get away with.

You can go quite a way with the picture adjustments to improve the range.

See Joshua Provost's posts on the settings. He's done an awful lot of research into it.

Jason

Ha .. funny, it was Josh who recommmended I shoot in Pro Cinema mode too. I have read the very posts you are talking about and have been having a bit of an interchange at CCD Pana user also. I'll do some experimenting with Pro Cinema and see how I feel about it. It's damn tough though because I can't play it back on anything to see how it looks ... 4:3 TV sadly!

You'll see it - it'll just be a bit squashed! [:p] <- that was meant to be a laugh smilie but I can't get them to work.

Jason