help? suggest affordable pro projector w' short throw lense (needs to be interchangable for future proofing)

[DusX]

I'm looking for suggestions for Projectors that have interchangeable lenses, and offer short throw (0.5 or less).
I need 3, so Ideally something that is not new to the market as I would like to pick them up at a lower cost.
1280x800 res would be fine... and 3.5k - 5k.

[Skulpture]

Interchangeable lenses on a short throw are quite few and far between. If you are looking for a 'look back' projector then i'd say there isn't one on the market due to the mirrors. 

We are using some laser Epsom projectors at the moment and they are amazing! I will find out the make and model. 

[Skulpture]

https://www.epson.co.uk/produc...

[DillTheKraut]

Panasonic does have those mirrored lenses for their higher professional class projectors with a ratio of 0.38 fixed. But only the ones above 6000 Lumen support them. PT-DZ6700 is an old model that does, but due to WUXGA and professional class, they are still not cheap. But even those have a lack of lenses between 0.38 and 0.8.

Best

Dill

[bonemap]

@dusx

I have also been using the Epson range of large venue projectors lately due to their competitive price and feature range. Particularly the 360 orientation feature (although they are not able to be rotated in 360 while in vertical orientation). The Laser lamp models cost a bit more but need to be considered in terms of their lamp longevity. They have interchangeable lens, although the ultra short throw options will add thousands to the overall cost - most lenses except the standard basic are going to add to the initial purchase cost as the projectors themselves ship without a lens.

They have built in corner, curved and stacking functions that make them very flexible for a range of installations. There are some models that are available with a black body casing.

They have the output power, flexibility and mobility that make them attractive for quick set- up event work. However, they do not match the grunt of Barco and Christie machines for larger installations and environments.

I purchased 2 x 8000 lumens Epson projectors for AUD$4600 each, built a cage to house both as a stack and have been using them for projections in parklands including a throw over a lake onto a steep hill side at 150 mtr. This is pushing the limits of the machines and is only viable due to a total absence of ambient light in that situation (a river gorge away from any urban development). I have used that same stack to project on to buildings within an urban space but at much closer proximity. It was here that I discovered that they are not truely totally 360. As I attempted to tilt the projectors up onto the building in side orientation, I got an error message indicating they would not tilt more than 15 degrees in vertical mode. The machines then proceeded to shut down. In the end I was forced to revert to projecting in the horizontal (which does allow the 360 rotation) and masking down the lens. I was a bit disappointed. 

I don’t know why I am telling this long throw story here, when the question was about short throw!

Best wishes

Bonemap

[DillTheKraut]

@bonemap said:

I purchased 2 x 8000 lumens Epson projectors for AUD$4600 each, built a cage to house both as a stack and have been using them for projections in parklands including a throw over a lake onto a steep hill side at 150 mtr. This is pushing the limits of the machines and is only viable due to a total absence of ambient light in that situation (a river gorge away from any urban development). I have used that same stack to project on to buildings within an urban space but at much closer proximity.

Sorry, if I'm trolling here a bit. But as it is a common inaccuracy, I want to help to get rid of this misinformation.

The proximity between projector and projection surface does only have a very little influence to the picture brightness (contrast to be exact). This is wrong thought, because if you move the projector to the direction of projection screen, the picture gets brighter. But this only happens, because the actual projection becomes smaller! If you zoom it to the size it had before, the brightness will become the same you had with the farther position.

Actually, the almost only factor that is influencing the max. projection brightness (with the same projectors power) is the size of the projection it self!

This is easily calculated:

Light power by lumen divided by the projection surface in m^2

example screen 16:9:
3m x 1,7m = 5m^2 to the projection surface
8000 lumen / 5^2m = 1600 lumens per m^2 wich is plenty and might be to much for some situations (hot spots, over lightning the surrounding area etc.)

10m x 5,6m = 56m^2
8000 lumen / 56m^2 = 143 l/m^2 wich is ok for dark surroundings

beware that the projection surface here is the real projection that the projector ist doing, not the one of the source! This means if the projector natively does 16:10 but your source and surface are 16:9, you have to calculate the 'virtual' 16:10 the projector is doing!
The logic behind it is simple. The projectors light power is distributed to the projection surface. The bigger the surface (even if it is 'virtual') that is projected to, the more the light needs to be spread.

This leads to an interesting situation with 3D mappings. If you project to 2 separate surfaces eg. a wall and a box, that is between the projector and the wall, the box will be slightly brighter. But this isn't because it is closer to the projector (I know, in this case this is the reason as well ;-P) but because the 'virtual projection' size is smaller.

This seams to be patty, but is essential to calculate the projectors power that is really needed!

The only factor why distance can have an influence to the brightness ist dust in the air. Because there is more in between projector and screen, the farther those are from each other.

Thanks and sorry to be an smart ass about this
Dill

[bonemap]

@dillthekraut said:

sorry to be an smart ass

It is always good to have robust discussion about technical aspects. I love the science behind projection and the physics of light, but it is not an area of complexity that I can claim any authority or depth of knowledge, I am a dumb ass when it comes to technical logistics.

I appreciate your comments and I will look into learning more about the technical aspects of projection design and adjusting my terminology to reflect the science better.

Best wishes

Bonemap