3 things I've been puzzling over.

1. It seems more or less accepted at this point that having the bulb perpendicular to the axis of the LCD results in brighter and/or more even lighting. However, I have only seen this discussed in relation to the 400W T15 or Ushio S400DD bulbs, both of which have an arc that is parallel to the length of the bulb. The bulb I'm using (150W Sylvania Metalarc / HSI-T 150W/NDL, pictured below) has an arc that is perpendicular to the length of the bulb. So, would I be safe in assuming that I should orient this bulb parallel to the LCD (i.e. along is width)?

2. If I affix a replacement SHC polar to my field fresnel, does that preclude keystoning? In other words, the polar must "lay flat" on the same plane as the LCD, correct?

3. In order to maximize light from my 150w bulb, I want to use a condenser fresnel with a significantly smaller FL than my field fresnel (165mm vs. 370mm). As I understand it, this will magnify the arc image at the triplet. So will using a reflector and condenser. OK, now the Million Dollar Question: am I better off with a smaller arc or more even light?

Alright, as usual I asked too many questions in one post and as a result nobody is responding. That's OK. I'm used to it

How about this: If I have a small arc (8 mm) and a small panel (~ 9 inches diagonal, 16:9) am I better off with a large or a small reflector/condenser setup (everything else being equal)? People talk about using a condenser with a FL that "matches" or "works well" with your rear fresnel and LCD, but I can't pin down what that really means.

I hate that dang sad face.

If I knew any answer to technical questions I'd answer.

I'd guess the long axis of the arc should always be oriented perpendicular to the long axis of the panel to make use of that orientation discovery.

We want both a small arc and more even light. Theoretically, a point source results in perfect dispersion of light and the highest degree of homogeneity at the projection screen. At least that's what I've gotten from what the smart guys around here say.

So much of this stuff is empirical. I think you'll have to do some experimenting to see what's best for you.

From my minimal experience I can say that your eye will tolerate an incredible amount of so-called vignetting so you shouldn't sweat it too much.

Edit: Don't those bulbs get a little tricky due to that nipple on the end? Shadows, etc.?

I understand and plan to do a lot of experimenting once I have everything assembled on a test bench. I just want to avoid wasting money, if possible, and zero in on the best components from the outset.



Hmmm... wouldn't know as I have yet to do a real test fire and so little info about these HSI-T bulbs can be found. One post in diyaudio suggested this bulb (with its small arc) made a big improvement in at least one setup. Wouldn't the nipple be more problematic when used face-on, rather than parallel to the LCD (as I am)?

Oh man are you ever in the wrong place!!! <just kidding>Yes and no. It all depends on your setup and type of reflector, etc. I'd assume (uh-oh ) due to the small form factor over all of that lamp it will require a high degree of precision placing it regardless of the type of setup you have. Smaller anything means higher precision is required in assembling components.

But I'm preaching to the choir ain't I?