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Taking pictures of TV screens

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Offline Andrew Fee

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Taking pictures of TV screens
« on: 14 June 2012, 04:32:42 AM »

David can you post your camera settings for these fantastic pics please. :)

David asked me to post a basic guide here for photographing displays. I'll try to keep things brief.

When taking photos of displays, for the best images you want to be using a tripod, have the camera in manual mode, and if you plan on editing them, you should shoot RAW files rather than JPEG if your camera supports it.

As far as edits go, the only editing I would really do is white balance adjustments, slight exposure corrections and cropping.

Camera basics:
  • ISO: As long as you're on a tripod, and aren't trying to photograph moving video (you should pause the image) you should set ISO as low as possible. ISO adjusts the camera's sensitivity to light, lower ISO means less sensitivity, but also less noise in the image, and more dynamic range.
  • Aperture: This adjusts how much light the lens lets into the camera. A lower number means a "wider" aperture, which lets more light in and lets you use a faster shutter speed, but it means you have a shallower depth of field. (less areas of the image in focus) Aperture will also affect image sharpness. Most lenses are sharpest around f/5.6 or so. If you go much above this, diffraction sets in, and will soften the image. (but more of the image will remain in focus) This can be used to your advantage—more on that later.
  • Shutter Speed: Shutter speed sets how long the camera opens the shutter to let light in to the sensor. If shutter speed is high enough, you can freeze moving images. (there are other ways too, but none relevant to this type of photography) As shutter speed gets slower, moving objects start to blur. If you're shooting paused images on a tripod, expect to use slow shutter speeds.
  • White Balance: This tells the camera what white is under the current lighting conditions. Usually the camera will do a decent job of things on auto, but you're far better off setting this manually to the TV.
So, the basics:
  • Don't shoot with a wide angle lens. If you shoot with a wide angle lens, you will have to get close to the screen (a bad idea for LCDs with their limited viewing angles) the image will be distorted, and if it's a zoom lens you're using, it probably isn't great optically at the wide end.

If you're using a zoom lens, you're best off somewhere in the middle to the end of the range, getting far back from the display. This should help reduce any viewing-angle induced effects, distortion, vignetting.

Here's a quick handheld photo of my screen with the camera on auto, up close with a wide angle lens as an example of what you don't want:


Notice that because this was hand-held, the image is somewhat askew, there's a lot of vignetting around the edges, viewing angle problems (corners are a different colour from the centre) and there's pincushion distortion. (lines aren't straight)

You might also notice the banding across the image. This is a moiré/interference pattern, which can be caused by a number of factors.
You can try slightly defocusing the image, moving closer to/further from the screen to try and eliminate it, or you can use diffraction at small apertures to your advantage.

I'd recommend using manual focus at all times when doing this (it's not like the TV or camera are moving anywhere) so first, focus the lens for maximum sharpness on the display—this will probably create a lot of moiré in the photo. Now put up a full white/grey pattern on the screen, and increase the aperture setting until it just disappears. (any higher and you will blur the picture)

Here's an image taken with an 18–55mm lens at f/22, rather than a 16mm lens at f/2.8:


Rather than being hand-held, the image was squared-up on a tripod, the camera is considerably further from the display, there's no vignetting, or viewing angle effects (colour is relatively uniform over the display) and there's no moiré. Because the lens is at 55mm rather than being wide angle, there's considerably less distortion as well. I've also set the camera's white balance off the display, which is why it's pure white rather than the overall image being discoloured.
  • White Balance. As mentioned above, in the second image, I set the camera white balance manually to the display (displaying greyscale patterns) which should give you far more accurate colour in most cases. Most cameras tend to tint the image blue as you see in the first image when it was set to auto.

You're probably best setting this off an 80% grey pattern rather than white though, especially if it's an LCD.

While it tends to work for most images, you can't always rely on this to work though. There are some that will need manual correction to look right. (of course this assumes the display you're editing on is also calibrated)
  • Pick a sharp frame. Even if you're using a tripod and doing everything correctly so far, you aren't guaranteed a sharp image. Rather than just pausing the film, spend a few extra seconds to go back or forward through a few frames to find one that's sharp.

It's an extreme example, but here's the difference that skipping forward a single frame can make:






  • Get the exposure right. If you've been following the guide so far, you've got the camera in manual mode, ISO is set as low as it can go, and you've adjusted the aperture so that you aren't getting moiré on the screen, this just leaves shutter speed to adjust the exposure of the image. (how bright or dark it is)

With ISO set very low, and using a small aperture, you're going to need quite long exposures—probably several seconds. If you're going to be taking photos that are several seconds long, you should use your camera's timer to avoid camera shake from pressing the shutter button. Set it to 2–3 seconds if you have the option, that should be enough, rather than waiting 10s for every shot.

More extreme examples, but here's a severely over-exposed image:

30 second exposure, ISO 200, f/22

Note the blown-out highlights, and how the letterboxing/background are now too visible. (note: I had to disable local dimming on my TV for this to show up)

Under-exposed image:

0.5 second exposure, ISO 200, f/22

Notice how dull the image is, and the complete lack of shadow details.

And here's a well exposed image (perhaps slightly under-exposed)

6 second exposure, ISO 200, f/22[/list]

And most importantly, pick interesting images. I went with Tron: Legacy because it was nearby, and tends to demo well. Wasn't actually a great choice for these examples though. The images David has posted are far more interesting.

In these examples, the room this TV is in was dark, but if you take the images with some lights on in the room (or better yet, daylight, if you can avoid reflections/glare) the image tends to "pop off the screen" more, as it does in David's shots.

There's more I could go into—learning to use a histogram will let you set exposure correctly in far less time, with a lot less experimentation—but this is already getting pretty long.

(Edited by David: moved to main forum)
« Last Edit: 14 June 2012, 04:48:45 AM by David Mackenzie »

Offline Vincent

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Re: Taking pictures of TV screens
« Reply #1 on: 14 June 2012, 10:21:21 AM »
Hi Andrew, long time no speak. What a fantastic first post.

White Balance: This tells the camera what white is under the current lighting conditions. Usually the camera will do a decent job of things on auto, but you're far better off setting this manually to the TV.

Personally, I prefer setting white balance to a real-life object (a white card, white piece of paper, etc.) under natural lighting, because 1) it's sometimes difficult to capture neutral greys/ whites on a plasma TV in different phases of its screen refresh; and 2) it may show up any colour cast on the display (which perhaps offers no/ faulty calibration controls, etc.).

(note: I had to disable local dimming on my TV for this to show up)

Off-topic, but which local-dimming TV do you have? I know you are very picky about your screens, so I'd be interested to know which one you finally settled on.  :)

Warmest regards
Vincent

Offline Scottthehat

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Re: Taking pictures of TV screens
« Reply #2 on: 14 June 2012, 11:28:19 AM »
nice explanation, but why f22.
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Offline Andrew Fee

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Re: Taking pictures of TV screens
« Reply #3 on: 14 June 2012, 04:04:17 PM »
Personally, I prefer setting white balance to a real-life object (a white card, white piece of paper, etc.) under natural lighting, because 1) it's sometimes difficult to capture neutral greys/ whites on a plasma TV in different phases of its screen refresh; and 2) it may show up any colour cast on the display (which perhaps offers no/ faulty calibration controls, etc.).
Setting the white balance off something in the room can work, but it means that how the screen looks is dependent on how close that light source is to D65.

If you're using small apertures and long exposure times, you should be able to avoid problems caused by the Plasma's screen refresh. (also an issue with sets that use LED backlight scanning)

If you're shooting RAW files and are going to be adjusting the white balance in software later, I'd probably just recommend you put up a pattern like this, and set it later:


This way if your white balance isn't perfect across the scale, you can pick what looks best for the overall image rather than a specific point. This is why I recommend using an 80% pattern rather than 100% if you're just going to set it in the camera off a single point. That tends to give better results than white does.

Off-topic, but which local-dimming TV do you have? I know you are very picky about your screens, so I'd be interested to know which one you finally settled on.  :)

It's a Sony 46HX903. I loved the design of the set, and while local dimming is visible at times, it's never been a distraction for me. (I'm used to CRTs where "blooming" is far worse)

It isn't perfect, but motion handling is good with backlight scanning, viewing angle isn't really a concern for me, and I'm happy to have excellent black level & shadow detail without the image noise, flicker and other issues that Plasmas have.

Had I known they would only have one year of using Sharp's RGB UV2A panels, I would probably have gone for the 52" model. From everything that I heard, the HX923 was a big step down, and now they don't even offer a full array local dimming model.

But now OLED displays are finally going to be available this year. I doubt I'll be buying one of the two that are going to be offered though—there already seem to be some issues with the design of them, and their price is out of my range. But in a couple of years, they'll probably be the best option available by quite a bit.

nice explanation, but why f22.
With my particular camera, the lens I was using, the distance of the camera from the screen etc, f/22 was the first aperture where there was enough diffraction to eliminate moiré.

It's far easier to see when you have a full field pattern up.

f/5.6:


f/10:


f/22:

Offline David Mackenzie

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Re: Taking pictures of TV screens
« Reply #4 on: 14 June 2012, 04:54:24 PM »
I never thought of exploiting diffraction to get red of moire. Will need to read more about that!
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Offline Scottthehat

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Re: Taking pictures of TV screens
« Reply #5 on: 14 June 2012, 05:45:56 PM »
as said by david using diffraction to get rid of moire is something new to me, will have a look and see what f number to use on my d700 will start at about f13 where defraction strat give or take a little.
the only thing about using large f number is if you dont wanna see your sensor needs cleaning  :o then you see big dust bunnys,
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Offline Andrew Fee

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Re: Taking pictures of TV screens
« Reply #6 on: 14 June 2012, 07:00:59 PM »
It's certainly not ideal, but it's the only way I know of that will consistently avoid moiré in your photos. (and one which requires the use of a tripod)
There's no other way to really "solve" the problem as it's all to do with the interaction of your camera's sensor size & resolution, the display's resolution and pixel structure, the quality of the lens you've got, how well focused your shot is (DSLRs tend to miss critical focus with phase-detection AF) how close you are to the display, and how sharp the camera's anti-aliasing filter is.

Essentially what you're doing is using diffraction as an anti-aliasing filter. Cameras which have stronger AA filters by default probably won't need you to use apertures as small as f/22. (my camera's AA filter is quite weak)

As you say, using small apertures like f/22 will definitely show up any sensor dust if you're using a DSLR. This is actually part of the reason I switched over to mirrorless cameras—they're significantly smaller, and cleaning the sensor is trivial because you have easy access rather than the sensor being deep in the mirror box—I use a NEX-5 because it's the smallest camera available with a full APS-C sensor.


There's definitely going to be some loss of contrast when doing this, but probably no more than you would lose from having a sufficient AA filter over the sensor to begin with, and you should still be able to resolve pixel-level detail.

There's less severe moiré in these examples, but this comparison shows off the loss of contrast. What you might also notice though, is that at f/5.6 the left side of the image is actually slightly out of focus. There's a couple of things that can cause this; a decentered lens, or simply having a shallow enough depth of field that even a slight misalignment will have some of the display out of focus. Shooting at f/22 avoids this because you have a very deep depth of field.

f/5.6:


f/22:


The loss of contrast, if it actually shows up in images, is pretty easy to fix though. You can either use a bit of extra sharpening on the image (all photographs require some degree of sharpening, which does not necessarily result in ringing) or add a bit of "clarity" if you're using Adobe's tools. In these examples, both have the same amount for a fair comparison though.

Offline tele1962

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Re: Taking pictures of TV screens
« Reply #7 on: 14 June 2012, 07:27:36 PM »
Andrew welcome to the Forum and thank you for your excellent posts. :)

Barry.

Offline FoxHounder

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Re: Taking pictures of TV screens
« Reply #8 on: 14 June 2012, 07:45:01 PM »
Thank you for very useful info, Andrew! I will study your posts a bit more, as it may help me very much at work. :)
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Offline RJ

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Re: Taking pictures of TV screens
« Reply #9 on: 14 June 2012, 09:11:31 PM »
Good post Andrew, and very useful. Good to see you posting too, I still remember some of your earlier posts on 'maximising image contrast', HW10 etc.

I do think the HX903 is underrated set when used on axis, I still have a 52" version here. Off axis, the picture starts to suffer, but that does not matter in he room it is in here. I have calibrated the HX923 and that is a good set too :)
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Offline Scottthehat

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Re: Taking pictures of TV screens
« Reply #10 on: 15 June 2012, 12:04:01 AM »
thanks andrew nice post, its not something a have ever really played about with tv photography, normally to busy photographing people, so will give it a try and see what i come up with.

also depth of field at f5.6 at 55mm on your 1.5x crop camera if you was about 6 foot away is 11 inches so well over the top depth of field,so the out of focus left side is nothing to do with that just difraction.
even at f2.8 it would be nearlly 6 inches.
« Last Edit: 15 June 2012, 12:10:04 AM by Scottthehat »
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Offline Andrew Fee

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Re: Taking pictures of TV screens
« Reply #11 on: 15 June 2012, 01:53:44 AM »
also depth of field at f5.6 at 55mm on your 1.5x crop camera if you was about 6 foot away is 11 inches so well over the top depth of field,so the out of focus left side is nothing to do with that just difraction.
even at f2.8 it would be nearlly 6 inches.
In theory that's correct, but a depth of field calculator really only gives you numbers for "acceptable sharpness" rather than "critical sharpness" which is far smaller, and much more apparent when you're shooting something like a test pattern rather than people.

A display is completely flat, so there isn't really any leeway when setting up the camera—even a slight misalignment can throw one side out of critical sharpness. (unless you're shooting at small apertures)

Most lenses don't have a flat field of focus either, so you tend to need a smaller aperture than a depth of field calculator will suggest if you need corner-to-corner sharpness. Just about anything other than Macros and high-end Prime lenses suffer from field curvature these days.

Offline Scottthehat

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Re: Taking pictures of TV screens
« Reply #12 on: 15 June 2012, 11:04:11 AM »
hi Andrew, i understand what your saying but as i said you have like 11 inches of dof and if you cant get a sharp shot of a tv with that then you really are doing some thing wrong.
Im a photographer and i own my own business and shoot lots of weddings and do alot of portrait work at low f numbers and unless your using long focal lenghts and big apature then you really shouldnt have a problem with getting what you want in focus.

but its great that you come along to help so welcome and thanks.
« Last Edit: 15 June 2012, 11:15:24 AM by Scottthehat »
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Offline tele1962

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Re: Taking pictures of TV screens
« Reply #13 on: 15 June 2012, 06:54:08 PM »
First real attempt. ???















« Last Edit: 15 June 2012, 07:00:39 PM by tele1962 »

Offline Scottthehat

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Re: Taking pictures of TV screens
« Reply #14 on: 15 June 2012, 07:02:43 PM »
Hay Barry looking good there mate.
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