Just a question, I'm constructing a lamphouse. Which bulb is brighter, a 36v 400w or a 24v 300w?

I have no idea Colin which lamps you are referring to, but anyone would assume in theory at least, without taking into account such factors as filament size, shape and focus through the gate, that the 36v 400w would be the brighter of two.

One is 24v 300w 2 pin SKU 2740, the other A1 270 36v 400w.

These are the two images I have just found for these lamps.
Both are capsule lamps but one has a tighter filament coil than the other. Other than that, they appear just from these photos I've seen, to be about the same for size and height of the filament etc.
If this is indeed the case, then if it were my decision, then I would probably plump for the 36v 400w type based on brightness performance alone.

Thanks for the advise Andrew. Would the bulb be more efficient vertically or horizontal infront of the mirror?

Vertically Colin, always and for safety reasons and for lamp life longevity.

Thanks Andrew, I'm on it.

I didn't know it should be vertical either :-) Not that I have ever constructed a lamp house.

Capsule lamps should always be mounted vertically Eivind. Just like they always were in our good ole fashioned slide projectors! 😂😂😂