Watching Over

by Vian Esterhuizen

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I am a member of a photography club. Each time we meet to critique, the pictures are projected on to a wall. Most of the folks complain that the picture quality is quite bad when projected. Unfortunately, switching projectors or finding a large screen is not an option.

What are some tips on taking pictures that look good both when projected and on a monitor?

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It may be worth taking a look at some of the answers on photo.stackexchange.com/q/21332/21; although this is looking at it the other way around, some of the points still hold true - the colour gamut of the projector, for example. –  Rowland Shaw Apr 19 '12 at 19:13
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If the goal is to receive feedback to make you better photographers...why would you intentionally shoot photos for the projector? Sounds like your club should have a fundraiser to buy a reasonable sized monitor. –  rfusca Apr 19 '12 at 19:34
    
@rfusca we might get better a projector eventually. in the meanwhile... –  publicRavi Apr 19 '12 at 19:46

4 Answers 4

up vote 11 down vote accepted

Projector native resolution needs to be taken into account. This will often be no higher than about 1024 x 768 in cheaper or older projectors. If you drive it at higher resolutions or at different aspect ratios it may convert internally but you are at the mercy of its processes.

A very major and often overlooked factor in using a projector is that what you see when the projector is turned off IS black, when the projector is turned on. The projector cannot "make" darkness - it can only add light to the starting black level. So, turn off the projector. That's black. If that is not black enough you need to do something about it.

  • Minimum to zero light level is one thing.

  • A screen should be used - a coloured wall changes your "black". The "screen" can be a roll of white paper (carefully rolled up afterwards or a cloth, preferably tensioned to make it ripple free.

I have found that ambient light reduction makes a stunning difference to otherwise poor results.

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Also make sure that projector's lamp is not close to the end of it's useful life. Some models may have lamps that change its color temperature or loose their full light output. Keep the lens clean too. –  Jahaziel Apr 19 '12 at 22:18

What, exactly, makes them complain about poor picture quality?

If you're shooting an uncalibrated projector toward an arbitrary projection surface, you've got a lot of things working against you. First of all, your color configuration is liable to be all over the place. Secondly, you're going to be at the mercy and the reflectivity of your wall.

I'd recommend a couple of things, assuming that the photos being projected look good on a a computer or on a mobile device.

  1. Calibrate your projector. This can be done by hand, but it's really worthwhile to invest in something like an X-Rite ColorMunki Display. This will quickly, automatically, and reliably measure the color performance of your projection system and create a software profile to correct for any deficiencies. If your club has a shared computer lab, you can use the same device to calibrate all of the displays in the lab.

    Also, be sure to set the projecting computer to use the projector's native resolution. If your projector is operating at 1024x768, but your computer's output is set to 1280x800, you're going to introduce all kinds of weird effects as the image is scaled and stretched to match the projector.

  2. If you're regularly projecting against the same wall all the time, look into buying "screen paint" or something similar. This is usually a neutral grey in color and may have additives to boost reflectivity. You'll find more info about this in DIY home theater forums. Note that you do not want to project against a black surface if you can help it.

  3. If you're not regularly projecting against the same wall, you might consider building a DIY projector screen. This could be as simple as PVC and a white bed sheet, or you could look into a more suitable screen surface. This can be built DIY for $100 or less, depending on your materials, and is something you can easily build in your garage in an afternoon.

Good luck.

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.@bright, welcome to photo.SE! –  Reid Apr 20 '12 at 17:55

It might be a wrong lead, but image quality in such case may be degraded by two factors:

1) a piece of software that does a bad job while scaling (bad interpolation of shrinked pixels), visible especially in pictures with high amount of grain, or patters that are prone to moire

2) a desktop that is running at resolution other than your projector's native

I can imagine that both of the above at the same time will create a real disaster!

I project my images on full HD calibrated projector, using standard XBMC server and believe me - there's no better way to enjoy your photos, so cretainly - something bad is happening there. Check your resolution and app that you use.

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In addition to Russell's excellent answer, I want to point out that there isn't just a single resolution to think about.

The projector will have a single native resolution, like 1024 x 768 on old or cheap models. However, the resolution setting of the computer driving the projector also matters a lot. Many projectors will auto-scale, basically resampling a video feed of different resolution into their native resolution. It's not good enough just to size your picture to maximally fit within a 1024 x 768 (or whatever your projector uses) landscape area, but the computer must also be set up to produce video at exactly that setting, and you have to make sure your picture is displayed on the full computer screen.

For example, let's say the projector is 1024 x 768, and your original picture is 4266 x 2844. Noting your picture aspect ratio is wider than the projector's, you scale the width to fit and the height comes out to what it comes out to. In this case, you make a version of your picture that is 1024 x 683 pixels in size.

So far so good, but that's just one step. Next you have to make sure the computer actually drives each of the projector's pixels directly without something doing resampling. That means you don't just connect the computer to the projector and randomly fiddle until you see something come out on the screen. You have to make sure the computer display settings exactly match the projector. This means deliberately setting it to 1024 x 768. Maybe you still get a picture with the computer set to 1280 x 1024, but it won't look good since the projector is resampling it to the 1024 x 768 it ultimately needs internally.

Two steps down, but you're still not done. You have to make sure your carefully sized 1024 x 683 picture is actually displayed across the entire computer screen, else the computer will be resampling your picture before sending it to the projector and it still won't look good. This means you don't just load the picture from a web browser or something. Those will put a border around the display window, and therefore show your picture in less than the 1024 x 683 pixels it is intended to be shown on. You have to use some software that is capable of showing your picture and only your picture on the screen, preferably with a black background. Such software certainly exists (including my own IMAGE_DISP program), but it's probably not your web browser.

So to recap:

  1. Make a version of your picture that maximally fits within the projector's native resolution.

  2. Make sure the computer output matches the projector's native resolution.

  3. Make sure your picture is displayed on the full screen of the computer.

Skipping any one of these steps will significantly degrade the final appearance.

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