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Archive 2013 · How to photograph projected images?
  
 
David-D
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p.1 #1 · How to photograph projected images?


I have a question and hoping someone can help.
Last night, I photographed a Birthday party (this can happen in Wedding reception too of course) and they have a projector that presents a photo slideshow. I tried to photograph the projected images and have some very strange effect. I have 2 issues.

1 - Color bands (I think something to do with RGB from the projector?), it looks like I have Red, followed by Green then followed by Blue bands over the projected image I have photographed:



and also sometime I have bad area on the image (as if the color was badlly saturated - see the baby's cheek on the image below):


Can someone please advise how should I photograph these and if there is any explanation?
Appreciated your help in advance.

Thanks.

David




Jan 12, 2013 at 10:32 PM
whtrbt7
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p.1 #2 · How to photograph projected images?


Longer exposure times, tripod, and custom white balance. You also need to line yourself flat to the screen and parallel to the projector. That should help. The color bands are normally caused by light refracting off of the screen. Same thing with the saturation blotches.


Jan 12, 2013 at 11:17 PM
David-D
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p.1 #3 · How to photograph projected images?


whtrbt7 wrote:
Longer exposure times, tripod, and custom white balance. You also need to line yourself flat to the screen and parallel to the projector. That should help. The color bands are normally caused by light refracting off of the screen. Same thing with the saturation blotches.

Thanks for those tips. Will try that the next time I have a chance.

What longer exposure times is recommended here? Thank you.



Jan 13, 2013 at 12:07 AM
scottam10
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p.1 #4 · How to photograph projected images?


I think there is an optimum shutter speed - too fast and you might see colour banding due to image refreshing, too slow and the image will be blurry cos you caught multiple frames. Just play with it. It is tricky to get a good shot though. You can also 'replace' the screen in photoshop later if you can get hold of the original projected image


Jan 13, 2013 at 02:16 AM
G-Gore
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p.1 #5 · How to photograph projected images?


My questions is - why even bother photographing the screen? Clients do know those pictures already, and most likely they have copy of them, and the slideshow too. It's the guests reactions worth capturing instead.


Jan 13, 2013 at 03:16 AM
whtrbt7
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p.1 #6 · How to photograph projected images?


Okie dokie, so the answer may have been too simple. It actually depends on the projector and the screen. Typically projectors that do digital images display at a rate of 60hz on refresh. This means the optimal shutter speed should be about 1/15. Why? I actually have no idea. Something to do with fighting the refresh on the LCD that is responsible for showing the image. Light can "bend" due to the screen used and due to how the image is projected. The problem with projected images is that the light is dispersed to the screen at wider angles in order to get the image blown up on the screen or wall. The refracted/reflected light will undoubtedly change the color and frequency of the light going into your camera. For this reason, I suggested that you pretty much be "on top" of the projector to reduce the amount of light bouncing around. So other than that, I would adjust your white balance to match the screen. Oh, and for practice, you can turn on live view on whatever you're using to get onto FM and adjust the shutter speed until you don't see the issues you mentioned.


Jan 13, 2013 at 04:39 AM
David-D
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p.1 #7 · How to photograph projected images?


G-Gore wrote:
My questions is - why even bother photographing the screen? Clients do know those pictures already, and most likely they have copy of them, and the slideshow too. It's the guests reactions worth capturing instead.


You are correct in saying we should capture the guests reactions but it would also be nice as well as having shots from the back of a venue (to include all the guests in the pic) to the front (where the screen is located) to show what was on the screen at the time that has caused the guests to have such reaction?

It's just like sometime I photograph a best man or groom writing his speech, I may want to take a shot on the piece of paper over the best man/groom's shoulder to show what was written on there.

Don't know if that make sense.



Jan 13, 2013 at 08:28 AM
David-D
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p.1 #8 · How to photograph projected images?


whtrbt7 wrote:
Okie dokie, so the answer may have been too simple. It actually depends on the projector and the screen. Typically projectors that do digital images display at a rate of 60hz on refresh. This means the optimal shutter speed should be about 1/15. Why? I actually have no idea. Something to do with fighting the refresh on the LCD that is responsible for showing the image. Light can "bend" due to the screen used and due to how the image is projected. The problem with projected images is that the light is dispersed to the screen at wider angles in
...Show more


Thanks for the tips re turning on Live View. Must try that whenever I have a chance. This is indeed sounds bit complicated. Simple work around to same the image = turn the image into Black and White



Jan 13, 2013 at 08:33 AM
 

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jprezant
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p.1 #9 · How to photograph projected images?


ZOMBIE BABYYYYY


Jan 13, 2013 at 04:18 PM
spink
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p.1 #10 · How to photograph projected images?


whtrbt7 wrote:
Okie dokie, so the answer may have been too simple. It actually depends on the projector and the screen. Typically projectors that do digital images display at a rate of 60hz on refresh. This means the optimal shutter speed should be about 1/15. Why? I actually have no idea. Something to do with fighting the refresh on the LCD that is responsible for showing the image. Light can "bend" due to the screen used and due to how the image is projected. The problem with projected images is that the light is dispersed to the screen at wider angles in
...Show more

60hz would be 60 updates per second. so I would think that any shutter speed below 1/60 should be fine. This is the same thing for shooting under florescent lights as they are also around 60hz.

Spencer



Jan 14, 2013 at 12:47 AM
qwyjibo
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p.1 #11 · How to photograph projected images?


If it's 60hz, you want to make sure to capture a whole number of cycles, i.e. 1/60, 1/30, 1/20, 1/15, 1/10.... I'm guessing that 1/15 is cited as the best time because of minor discrepancies between the projector and camera in terms of exact fractions of seconds.


Jan 14, 2013 at 01:02 AM
camerausername
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p.1 #12 · How to photograph projected images?


jprezant wrote:
ZOMBIE BABYYYYY


I'm going to have nightmares tonight.



Jan 14, 2013 at 03:29 PM
eNoBlog
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p.1 #13 · How to photograph projected images?


I always have an issue with color balance when there's a person in front fo the slide show, as in this next shot. If I color balance for the real person, the projected image will not have the same colors I saw in real life. Not sure what's going on there, but IMO, it's a losing battle. Or maybe selective WB would do the trick. I haven't experienced the banding you show. Going for slower shutter speeds will not work in most situations I run across.



Jan 14, 2013 at 06:21 PM
3ntreri
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p.1 #14 · How to photograph projected images?


DLP projectors have a spinning color wheel in front of the micromirror device. Basically it can only display one color at a time so it cycles through all of the colors it needs in fast succession so that it all looks like a single full-color image to the human eye.
If your shutter speed is too fast it'll only catch a portion of the projected image. Keep your shutter speeds low (~1/10-1/20th) to avoid the issue.

LCD projectors don't have the same problem



Jan 16, 2013 at 11:09 PM
David-D
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p.1 #15 · How to photograph projected images?


3ntreri wrote:
DLP projectors have a spinning color wheel in front of the micromirror device. Basically it can only display one color at a time so it cycles through all of the colors it needs in fast succession so that it all looks like a single full-color image to the human eye.
If your shutter speed is too fast it'll only catch a portion of the projected image. Keep your shutter speeds low (~1/10-1/20th) to avoid the issue.

LCD projectors don't have the same problem

Thank you for the tip. Will have to keep that in mind to try the next time I come across such situation



Jan 25, 2013 at 07:20 AM





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