How powerful projector do I need?

[Matthew Giles]

I have a stage wall roughly 5m diagonal in size. If I'm projecting from 5-10m away, how powerful projector am I going to need to get a good image?

I've probably got a choice between an Optoma EX762 and a Panasonic PT-D5700 Projector.

It's likely there would be other stage lighting and washed, but could be completely dark if necessary.

 

[Amiers]

Go with the Panasonic.

 

[J Katz]

This boils down to image luminance. if you want a good projected image, the image needs to be bright enough to be easily seen.

Factors at play:

• Projector Brightness (Lumens)
• Screen Reflectivity (Gain)
• Screen Size
• Atmospheric or Room Lighting

With a projector output of 6,000 lumens placed around 30' away with a screen size of 5 meters diag. You should have around 40+ Foot-lamberts which is plenty in most situations but your ambient lighting will need to be somewhat dim.

Two great reference to dig deeper:
https://www.residentialsystems.com/res-blogs/1156
https://www.projectorcentral.com/Panasonic-PT-D5700U-projection-calculator-pro.htm

 

[ruinexplorer]

How "bright" of a projector is only one part of the question. A shoot from the hip between the two projectors that you offered, I would agree on the Panasonic.

Factors to consider when using a projector:

1. ANSI Lumens. If you look at off brand projectors, there will often be a lumen rating higher than ANSI lumens. The reason is that they will often only look at just the center lumens (will be brighter than the overall image), but they do not compensate for the human visual system, in other words, they measure the entire spectrum, which is greater than what range people see.
2. Contrast Ratio. This is the variance between white and black of the projected image. There are two ways that manufacturers will list this. The most common will be very dramatic (several thousand to one). First, they will measure a full white image to a full black image. This can be helpful in determining how bright your video black image will be. "Dynamic Contrast" is a manufacturer's way of misleading the customer by reducing the output in order to increase contrast and using the measurement of full black to full white. In order to have a good quality image, you should look for ANSI contrast ratio. This will be considerably lower, with a "good" ratio at about 1000:1. This is measured by having a "checkerboard" of white and black (8 of each) and taking measurements at the center of each. This will help determine how well your image is perceived. It can even make an image appear "brighter" than an equally luminous projector with a lower contrast ratio.
3. Imaging technology. LCD, DLP, LCoS (all names) create the image slightly differently. The biggest difference in how "bright" an image will be is a single-chip DLP. A shoot-out of a white image will look the same, but as soon as you start having anything with various colors, then it will look darker. Also, LCD often has greater light spill, lowering the contrast ratio.
4. Illumination technology. Lamp based technology is inefficient. In particular, for most lower powered projectors, they use a high-pressure lamp that peaks in the red range. In order to get a full range of color, much of that is discarded, but can still escape the projector, hurting your contrast ratio. Higher brightness projectors often use Xenon lamps, which have a better color rendering, but have a shorter lamp life. Newer projectors use LED and Lasers for lamp-free projection.
5. Projection surface. The color and amount that the surface scatters the light play a great deal in how the image looks. Most people wanting to find out how "bright" of a projector that they need are planning on projecting on a wall or the cyc. This doesn't give you any information the way a manufactured screen will (in order to help you plan). In general, we just figure that the image brightness should be de-rated by about 20% to compensate for a non-ideal surface.
6. Size of image. You are looking at a 4:3 aspect ratio projector. Most often, when people want to add projection to their theater production, it is to replace a backdrop. Those are generally much wider than they are tall, even exceeding 16:9 projectors. However, even if you are looking to have a wide image, then you are expanding your current projection (blanking what you don't need) and losing a lot of lumens (there are only so many, and the more you spread them out, the less bright they seem).
7. Resolution. This affects the quality of the image. For the best image, match what is going in to what the projector natively produces. In the case of your projectors, that is 1024x768.
8. Ambient light. Any light that gets on your projection surface that is not a part of the projected surface is bad. It reduces your contrast ratio (see above). It takes very few lumens to negatively affect your image. Most ambient light is indirect (as the lighting designer should take care to shutter off the surface). Front light is often your enemy as it will bounce off the floor onto your projection surface.
9. Content. Depending on what you are trying to show can change how bright of a projector you need. The brighter the content, the easier it will be seen.

This should give you some things to consider when looking for a projector.