filming titles from a laptop screen

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Haydocklad
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filming titles from a laptop screen

Post by Haydocklad » Thu Oct 24, 2013 10:18 am

Hi Has anyone tried to do this? Do you need to adjust the exposure from the camera's automatic reading? Cheers Mike

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S8 Booster
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Re: filming titles from a laptop screen

Post by S8 Booster » Thu Oct 24, 2013 11:42 pm

i did this long time ago with somewhat outdated K40. shot it wide open from my MacBook screen and the results came out very good. hard to recommend settings for new film stocks - suggest you do a trial and error test.

my sample: http://www.youtube.com/watch?v=wVDzOGuB7ok

shoot...
..tnx for reminding me Michael Lehnert.... or Santo or.... cinematography.com super8 - the forum of Rednex, Wannabees and Pretenders...

carllooper
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Re: filming titles from a laptop screen

Post by carllooper » Thu Oct 24, 2013 11:59 pm

The only way to know is to compare camera auto measurement with a light meter reading. In other words don't use auto - use a light meter.

When filming off a screen, ensure there's no extraneous light falling on the screen, eg. shooting in a darkened environment where the screen is the only light source. Basically you want to avoid reflections and general flare on the screen.

For exposure, the recommended procedure would be to take a shadow reading and a highlight reading, add the two together and divide by 2. In the case of a laptop screen the shadow reading would be one done on black pixels and the highlight reading done on white pixels. So the process is:

1. take a reflected light meter measurement of the light given off by

a. white pixels
b. black pixels

2. Add the two measurements together, and divide by 2

EXAMPLES

Example using EV measurements (easiest)

white = 7.2 EV
black = 1.8 EV

EV = (white + black)/2
EV = (7.2 + 1.8)/2
= 4.5

Example using f numbers (example numbers here are those one might read for a 1 second exposure - so are not typical - but the method is the important thing)

white = f/22 + 6/10ths of a stop
black = f/1.4 + 2/10ths of a stop

MATHEMATICAL METHOD

1. Convert white and black to log2 scale: e = log2( f^2)

white = log2(22^2) + 0.6
= 9.5

black = log2(1.4^2) + 0.2
= 1.2

2. Add the two values together and divide by 2
(9.5 + 1.2) / 2 = 5.35

3. Convert result back into an f number

fnumber = sqrt( 2 ^ e)
= sqrt( 2 ^ 5.35)
= f/6.3

which is somewhere between f/5.6 and f/8

SEMI-INTUITIVE METHOD

Write down on a peice of paper the following

0. 1
1. 1.4
2. 2
3. 2.8
4. 4
5. 5.6
6. 8
7. 11
8. 16
9. 22

From this we can see that f/5.6 is half way between f/1.4 and f/22, so the ballpark aperture you need would be:

f/5.6

Alternatively, add the corresponding left column figures together (1 + 9) and divide by 2, the answer being: 5
The corresponding fnumber, for 5, is:

f/5.6

And if one wants to be pedantic (and why not) then add the fractional parts of the readings together, and divide by two, which would be (0.2 + 0.6)/2 = 0.4,

so answer would be: f/5.6 + 4/10ths of a stop

Carl
Last edited by carllooper on Fri Oct 25, 2013 12:37 am, edited 2 times in total.
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richard p. t.
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Re: filming titles from a laptop screen

Post by richard p. t. » Fri Oct 25, 2013 12:25 am

In general when shooting off a monitor you struggle for light. If using say a 100 or 200 asa film stock, the likelyhood is that your best exposures would be between maximum aperture and say 2.8. Simplest thing to do is to shoot the titles two or three times. Once at maximum, then a little more closed.
Focus is going to be an issue too. Don't focus by eye. Trust the marking on the lens and use a tape measure.
Colour won't be 'exact'. A normal LCD type screen is 'about' daylight coloured, so make sure you shoot with or without the appropriate filtering (ie with daylight film, no filter)
I run Nano Lab - Australia's super8 ektachrome processing service
- visit nanolab.com.au
richard@nanolab.com.au

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BAC
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Re: filming titles from a laptop screen

Post by BAC » Fri Oct 25, 2013 4:58 am

I shoot titles from my computer screen all the time with good results. I type it up in MS Word with a large bold font with white letters on a black background. I take a careful measurement from the screen to the film plane to make sure the focus is correct. I shoot it with the aperture wide open, sometimes I even slow the frame rate to 12fps. Make sure you're not filming anything outside the black background. Some cameras like non-reflex models may need parallax correction. The black background works great if you want to back wind the film and fade the title in or out. I've done this with a large HD computer screen as well as a laptop screen when I'm traveling, both with good results. I've mostly done this with E100D film in Super 8 and Regular 8mm.

Haydocklad
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Re: filming titles from a laptop screen

Post by Haydocklad » Fri Oct 25, 2013 10:57 am

Thanks everyone for the good advice!

pip
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Re: filming titles from a laptop screen

Post by pip » Fri Oct 25, 2013 5:44 pm

I have set up the titles on powerpoint. i can't seem to get a large enough black background with Word. I have simply fixed the aperture on the white screen (using the camera's autoexposure) then reverted to the screen with the title with black background. However, on checking this recently with a new laptop, I noticed the autoexposure was in the red area in the camera's viewfinder. It seems the old PC gave greater screen illumination, because the autoexposure never registered in the red area. I am not sure therefore where to set the exposure now - maybe just leave it on autoexpose. I don't really want to experiment too much, because film for projection is very expensive now, and super 8 does not have any arrangement like notched titles which must have been very economical for 9.5.

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Re: filming titles from a laptop screen

Post by carllooper » Mon Oct 28, 2013 4:20 am

pip wrote:I have set up the titles on powerpoint. i can't seem to get a large enough black background with Word. I have simply fixed the aperture on the white screen (using the camera's autoexposure) then reverted to the screen with the title with black background. However, on checking this recently with a new laptop, I noticed the autoexposure was in the red area in the camera's viewfinder. It seems the old PC gave greater screen illumination, because the autoexposure never registered in the red area. I am not sure therefore where to set the exposure now - maybe just leave it on autoexpose. I don't really want to experiment too much, because film for projection is very expensive now, and super 8 does not have any arrangement like notched titles which must have been very economical for 9.5.
If you lock the aperture to what it reads for just a blank white screen you'll get an under-exposed image: the whites will come out grey instead of white (although the blacks will certainly come out black)

For titles that are just white letters on black I'd suggest just opening the aperture as wide as it goes (or what amounts to the same result: lock the auto aperture while the camera is looking at black, ie. with needle in red area) and you should be fine. The blacks should stay black because even with 200ASA film I don't think the film would be sensitive enough to render the laptop blacks as anything much more than black. And if auto aperture is reading the titles as in the red area then you definitely won't have any problem with blacks staying black. Your only concern would be the whites - but if the aperture is widest open, and if the whites weren't reading in the red area (as you mentioned and is also likely) then they'll remain white (rather than coming out grey). Or to put it another way - with aperture wide open the white can't get any more white.

But to be more precise: what aperture are are you getting when reading just a white screen - and what is the smallest f-stop reading on your camera (f/1.4 ?). And lastly what ASA is your film?

C
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pip
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Re: filming titles from a laptop screen

Post by pip » Mon Oct 28, 2013 2:59 pm

The camera, Nikon R10, was showing an aperture of about f2 with Ektachrome 100d. The camera's maximum aperture is f 1.4. Is it the case that modern tablet like PCs have less screen illumination than older desk top PCs?

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Re: filming titles from a laptop screen

Post by jpolzfuss » Tue Oct 29, 2013 5:23 pm

pip wrote:Is it the case that modern tablet like PCs have less screen illumination than older desk top PCs?
As a rule of thumb a "normal" monitor is brighter than a monitor that can be used as a touch-screen.
As another rule of thumb a "normal" monitor is brighter than a battery-powered monitor (at least at the default settings - but most tablet-PCs do have a "brightness"-control to change this :wink:)
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Re: filming titles from a laptop screen

Post by carllooper » Tue Oct 29, 2013 11:13 pm

pip wrote:The camera, Nikon R10, was showing an aperture of about f2 with Ektachrome 100d. The camera's maximum aperture is f 1.4. Is it the case that modern tablet like PCs have less screen illumination than older desk top PCs?
Yeah - so just use your widest open aperture (f/1.4) and you'll be fine.

The whites will still be a tad under-exposed (rendering a touch towards grey) but not much you can do about that since you can't open the aperture any further. But if you can also shoot at a slower frame rate (eg. 12 fps) along with the aperture wide open, you'd be able to get the whites a stop whiter. The blacks will stay black either way: with the aperture wide open the blacks would only start to render as less than black if you were reading white as something like f/4 or more, (f/5.6, 8, etc).

C

ps. the laptop I've got here is reading about 4 stops difference between black and white. So if I were reading white as f/2, then black would be reading as f/0.5, and the optimum (midpoint) exposure setting would then be f/1 (half way between). But of course not many lenses facilitate f/1. If the camera's maximum open aperture can only get f/1.4, then the alternative is shooting at half the frame rate and f/1.4, and this would yield the same exposure as if shooting full frame rate @ f/1. However with high contrast titles it isn't super-critical - you can be up to a stop off the optimum exposure and still get good to excellent results.

pps. an alternative is to use a desktop screen. They are brighter and have greater contrast (7 stop range on the one I've got here). For high contrast titles the greater the screen contrast the less critical will be your exposure setting - ie. you could be out by 1 to 2 stops of the midpoint and still get a good high contrast result.
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