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Old June 17th, 2006, 09:19 PM   #61
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Quote:
Originally Posted by Steve Oakley
Ouch... there is a lot of bad math & procedure going on here.

Steve Oakley
Steve, I did use a waveform to check the levels, I had used the vector first just to check where the 18% gray fell, and I had vector on the brain.

If you look at my original post, you will notice I used a grad to check the ISO of the camera, I come up with a 320 ISO using the grad.

This test was for Paolo: "Out of respect to Paolo, I just did a more comprehensive test using just a 18% gray card instead of a grad."

The stock lens is T1.5 at 16mm and T2.0 at 88mm with the falloff starting to kick in at about 55mm.
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Old June 18th, 2006, 12:33 AM   #62
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Originally Posted by Steve Oakley
Shutter -- the proper shutter for 24P is 1/48th, or 24FPS on your light meter. For 30P, I prefer to shoot @30th, but techincally you should be using 1/60th. For me 1/60th is just regular videV looking, so I opt for the slower shutter speed, which is a one stop gain. very usefull in low light.
It's interesting that with the original JVC, I insisted that 1/60th was correct because 1/48th would be correct for 24p. Now I'm beginning to find 1/30th looks a lot less electronically "strobby" on the original JVC.

But, logically I can't justify why 1/48th looks good at 24fps, but a much slower shutter looks good at a slightly higher frame rate.

One possibility -- not often discussed (and OT) is that the nature of a film shutter's pass across a frame of film is different than the full frame shutter opening done in video.

If SOMEHOW the moving wedge shutter of the film camera's shutter yields it's own motion blur -- then the 1/48th number is not completely valid, The extra moving wedge blur might yield a true film shutter speed lower than 1/48th.

Alternately, the instant ON/OFF of an electronic shutter might make 1/60th LOOK more like a higher shutter-speed. For example, 1/96th. So, when we drop a video shutter by 2 to 1/30th -- the EFFECTIVE LOOK drops to 1/48th.

Either way, I'm convinced, that the electronic shutter -- even when set exactly to that of a film camera -- does not produce the same result. The electronic shutter seems to create more severe judder on motion.
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Old June 18th, 2006, 12:41 AM   #63
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Originally Posted by Enzo Giobbé
Out of respect to Paolo, I just did a more comprehensive test using just a 18% gray card instead of a grad.
Thank you Enzo.
I won't even try to digest your numbers at this late hour (10:30pm) after a pretty intense day of shooting the first episode of "2nd Unit" :)
I just wanted to thank for your time and insight. I will take a look at your post tomorrow when I'll have the right energy to appreciate it :)
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Old June 18th, 2006, 12:47 AM   #64
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Originally Posted by Stephen L. Noe
Didn't Adam Wilt and the boys figure the ISO at just under 320?
Yes, and I never meant to doubt his numbers, it's just that in his article he didn't mention the gamma type and value that he used. I assume that it was the factory settings. I wanted to check the value of TC3 because I noticed that the camera changes sensitivity to light based on the gamma settings. Try this for fun: Set gamma at "CineLike" -1 as per TC 3. Adjust the iris for what you consider correct exposure of the scene. Go back to the menu and switch to gamma "Standard" with the same -1 value. Your scene should become immediately much brighter.
Maybe Enzo or Steve or anybody else :) can explain what's happening when you do that. The way I interpret it is that the camera is more sensitive to light with Standard gamma and so the ISO speed depends on the type of gamma selected.
Or maybe I'm allucinating :)
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Old June 18th, 2006, 02:19 AM   #65
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Quote:
Originally Posted by Steve Mullen
You guys are so far ahead of me that I'm going to try to repeat back what I think I understand:
Eat more pasta! :)

Quote:
The stock lenses F stop range is from f/1.4 to f/1.8. Thus, the average F-stop is f/1.6. Correct?
Steve, first of all we are talking two things. One is the quasi ISO of the camera (this is the film speed set on the meter). Two is the actual f stop to T stop conversion (we need a number to set the lens aperture to).

Since the lens is calibrated in f stops, we have no choice but to make the T stop conversion. The stock lens is f/1.4 to 1.8, but T1.5 to T2.0, so I called it T1.8 across the zoom range of the lens. If you shot wide all the time, then you could use T1.5, if you shot in the 60 - 88mm range most of the time, T2.0 or T1.9 would work. MY aim was to arrive at an f stop reading on the meter that would transfer directly to the lens using Paolo's 18% gray measurement system.

This would keep Paolo from having to tell the 1st AC "4.5 plus 10%" :) I actually do all such conversions in my head, preferring to keep my meter at 1/48 unless I am under or overcranking.

Quote:
8)(A) You DECREASED rather than INCREASED the shutter-speed which would bias toward under-sposure. This ie reverse of what I think needs to be done get the correct exposure. (B) You mention a 1/30th shutter-speed. But, 30p uses a 1/60th shuttter-speed. (24p uses a 1/48th shutter-speed).
You are correct. I counted down 1/3 - 1/2 instead of up, my bad. And yes, I set my meter at 1/48 for film and PAL video, and 1/60 for NTSC video (double the 1/24 and 1/30 speeds I used in my example).

Quote:
Would it be any different for a reflective meter?
Not if you were shooting a 18% gray card. I only use a reflective meter to measure contrast ratios.

Let me set Paolo's system aside for a minute. By using a grad (instead of Paolo's solid 18% gray) and the factory defaults, I think I achieved a more accurate overall luminance reading for the base ISO camera setting.

Using my system, I came up with a quasi ISO setting for the HD100 of 320. However, Paolo (using his TC3 settings) came up with 200. Now we know that the gamma setting will change the overall exposure curve, so that may account for the difference in Paolo's ISO vs. mine.

Paolo's methodology, however was entirely correct. Exposure meters live in a 18% gray world.
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Old June 18th, 2006, 09:47 AM   #66
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Originally Posted by Paolo Ciccone
Yes, and I never meant to doubt his numbers, it's just that in his article he didn't mention the gamma type and value that he used. I assume that it was the factory settings. I wanted to check the value of TC3 because I noticed that the camera changes sensitivity to light based on the gamma settings. Try this for fun: Set gamma at "CineLike" -1 as per TC 3. Adjust the iris for what you consider correct exposure of the scene. Go back to the menu and switch to gamma "Standard" with the same -1 value. Your scene should become immediately much brighter.
Maybe Enzo or Steve or anybody else :) can explain what's happening when you do that. The way I interpret it is that the camera is more sensitive to light with Standard gamma and so the ISO speed depends on the type of gamma selected.
Or maybe I'm allucinating :)
Yes, I see the need to describe the difference in ISO when settings are placed in the camera which change the gamma curve. If the TCV3 scene file is the max contrast the camera can produce then you should get a lower ISO value than stock settings. I struggle with this because in uncontrolled lighting (outdoor) the image get's shot to hell with overexposure and blooming (in the primary reds and secondary yellows) and the stock settings are more favorable for a more balanced look. It's odd because with a film camera, the film's speed is the constant in the equation and with the JVC, the ISO floats depending on what scene file you select. Solid work guys. It goes a long way in explaining where and why there is such a difference between scene files (not just color but the full gamut).
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Old June 19th, 2006, 09:33 AM   #67
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Originally Posted by Enzo Giobbé
Panavision Super 35. Hahaha, that solves the DOF issue, that's for sure :)
Oh yeah! And the cost of the rental for the lens is probably higher than the cost of the HD100 :)
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Old June 19th, 2006, 09:41 AM   #68
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Paolo- I love the improvement with your TC3 settings, but... how would you modify it to really saturate reds and greens, without blowing out?
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Old June 19th, 2006, 09:49 AM   #69
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Quote:
Originally Posted by Enzo Giobbé
Eat more pasta! :)
In the USA most of us on diets because we don't drink enough good wine!

"You are correct. I counted down 1/3 - 1/2 instead of up, my bad."

OK -- now it all makes sense.


"Not if you were shooting a 18% gray card. I only use a reflective meter to measure contrast ratios."

1) If I were setting exposure with an 18% card/cloth I would use my meter in Reflective Mode to measure the light reflecting from the gray. Correct?

2) If I were setting exposure, I could also measure light falling on an AVERAGE scene using Incident Mode. Correct?

3) If I were computing contrast ratios -- which is for me the main reason to use a meter -- I would use my meter in Reflective Mode to measure the actual light reflecting from each area within the scene. Correct?

In all cases, I would set shutter-speed appropriately for 24p or 30p.

Now comes the question of which ASA to use.

1) Some say the ASA varies by WHICH gamma curve is selected. Can anyone demonstrate/calculate HOW Enzo's and Paolo's selected gamma setting actually would cause the difference between 200 and 320?

2) Some say the ASA varies by whether you have low or bight illumination. This is why some have claimed, the camera has several ASA values. I can't understand this.


Lastly, a dumb question. I take my old JVC HDV camera and point it at an average daylight scene. I set the camera and my lightmeter to 1/60th. I read the F-stop from the camera. Now I measure the EV of the scene. Using the F-stop and EV I find the ASA that matches. Why isn't that the camera's ASA?
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Old June 19th, 2006, 10:32 AM   #70
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Quote:
Originally Posted by Enzo Giobbé
Out of respect to Paolo, I just did a more comprehensive test using just a 18% gray card instead of a grad.
Thank you my friend.

Quote:
I came up with an absolute ISO value of 250 at a 24 shutter/108% clip and 200 for a 30 shutter at 100% clip.
Makes perfect sense. I just wanted to highlight, in case is not clear to everybody, that different shutter speed implies more/less light exposing the "frame" and that explains the difference in ISO rating. Thank you for testing the two different situations, my original test was only at 24fps. Your numbers give us a more complete picture.

Quote:
For myself and Paolo, who are just simple Italians...
Hehehehe.

Thanks again Enzo, that was very useful and informative.
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Old June 19th, 2006, 10:35 AM   #71
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Originally Posted by Keith Forman
Paolo- I love the improvement with your TC3 settings, but... how would you modify it to really saturate reds and greens, without blowing out?
Thanks. If you want more reds please see the V2 on my web site. By changing the blue gain you end up with more reds. I wouldn't touch the green because it has side effects on the whole color matrix, just too complex. Also, if you like more or less saturation I would achieve that in post. Remember TC is not meant to be a look but a way of bringing the most information into your camera. If you want more saturated reds and green I would use the color correction of your compositer/NLE.
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Old June 19th, 2006, 10:42 AM   #72
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Thanks Paolo. The reason I ask, is because I am shooting a family of Cardinals in my back yard. Brilliant red against lush greens, and it just isn't capturing quite right. Of course, I also don't have any way to capture to the PC yet, or to view externally. I'm working on it.
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Old June 19th, 2006, 11:46 AM   #73
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Originally Posted by Keith Forman
Thanks Paolo. The reason I ask, is because I am shooting a family of Cardinals in my back yard. Brilliant red against lush greens, and it just isn't capturing quite right.
I see. For "lush green", if you're shooting under bright sunlight, I would use a polarizer. That should make the foliage become much better.
In absence of that use the built-in ND.
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Old June 19th, 2006, 11:56 AM   #74
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Use a polorizer... I should have thought of that. I still haven't received my UV filter yet, and I knew I should have added a Polorizer... (slaps forehead!) Thanks!

By the way, where is the sweet spot on the 16x lens?
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Old June 19th, 2006, 12:13 PM   #75
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Originally Posted by Keith Forman
By the way, where is the sweet spot on the 16x lens?
There is a post by Tim Dashwood about that, do a search in the past articles.
I think it's around f4.0 but Tim has a complete description of it.
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