Cineversity

Thanks for your patience with my explanation, Alex.

I really want that everyone reading along understands it.

If there is a different model, let. I know. I think then it is time to create a user-data field as per your request.

Enjoy your weekend

Hello Sassi

Well I think there is certainly a fair amount of technicality involved with this topic, specifically when it comes to optics and sensors etc…
But I think that having a system where you can easily specify certain values such as
1/Resolution
2/Throw ratio
3/Focal length
4/Zoom
5/Shift
Would allow for a coverage of all the cases.  Sometimes just resolution and throw ratio are enough, as they give you the basic information to setup a very rudimentary environment…

Yes, that is certainly needed, Alex.

Resolution? Besides aspect ratio and square/squeezed pixels (footage), I would have no idea how that could be influenced.

As mentioned, some have the “shift” options more comfortable than others. That would be a little bit more complex setup to chose from.

Points 3 and 4 would be the same, with a different label.

The chip size is the core factor in all of that. If that is not known, none of the others with lead to anything.

In my experience, going by my collection of over fifty lenses, the focal length is pretty much never correct. I would always feel uncomfortable trusting specs on paper.

All the best

Yes sorry, resolution should be aspect ratio…
Agreed about lack of clear specs…but in the projector industry the typical calculations in tools like Mapping Matter or Disguise are always done roughly with the numbers I outlined.  There is always a bit of error, but it can all be corrected on site with minor adjustments, so it isn’t considered essential for previz purposes.

Yes, I agree, Alex.

I mention the problems more based on the concerns that anyone reading along, using the set-up, runs into trouble and blames the set-up.

For any projection, especially practical-camera-projection, the position where the lens (nodal point) is the main key. Since it is always a point light source, even shifted, the projection from that point can be adjusted (shifted, rotated, “zoomed”). I hope I make sense here. I refer to a presentation where people used parallel projection for camera project to simulate the practical set up, which can only fail.

Again, I try not to be right here or nit-pick. It is more like a label “your results might vary!”

During my light-show time, I did 135 gigs/concerts with a full truck-load of lights, including ten slid projectors. Most of them were specialized (color oil, polarization, etc.). I had to adapt to many stages and spaces, so I have a passion for this work

Thanks for your input.

Cheers

Ah yes of course, that makes sense!
Yes I agree on the position of the lens, but I think typically when people do this kind of study in C4d they are getting a general idea and if they need to be really precise they are dealing with high end projectors for which all the specs are clearly laid out in the product sheet (which is not the case for these cheaper office type projectors).

Wow I’d love to see the stuff you did in those times.  Were you using Pigi projectors?

Yes, Alex, everything has more predictability with pro gear, and it is more fun when it works that way.

Off-topic.

My light show activities are way back in time. I hand-colored 500 slides, for example. I matched three series to be blended with three projectors to create unlimited patterns. (I had found a mixture of paint and ink that chemically reacted and produced organic and superfine patterns. I had run them with fog machines on the stages, etc. Or crumpled polarization film run against a rotating pol filter, which resulted in moving colored chrystal-like projections, over-layed with these fluid color oils (rotating).
Later I saw Nektar’s (Fantasia Light Circus) Mick Brockett doing in super large what I did in smaller (up to 2000 people) venues, to name an example.
All analog.

Thanks for the interest.