Since upgrading from a 2000 to a 4000 lumens OHP I have noticed a bright spot in the centre of my projection that I believe is caused by the fresnel in the OHP. This is particularly distracting on darker films/scenes.
I have read in another thread that this problem can be solved by placing some scotch/sellotape over the centre of the fresnel, but this doesn't appear to make any difference. A small piece of opaque tape over the same spot stops it, but then you get a dark spot in lighter films/scenes, so that's no good.
Does anyone else suffer from this problem? How do you deal with it?
Can it be made worse by the fresh rate of the LCD? I'm using a Spectra C. The OHP is a 3M 1750. There is no evidence of this spot whithout the panel on the OHP.
I have read in another thread that this problem can be solved by placing some scotch/sellotape over the centre of the fresnel, but this doesn't appear to make any difference. A small piece of opaque tape over the same spot stops it, but then you get a dark spot in lighter films/scenes, so that's no good.
Does anyone else suffer from this problem? How do you deal with it?
Can it be made worse by the fresh rate of the LCD? I'm using a Spectra C. The OHP is a 3M 1750. There is no evidence of this spot whithout the panel on the OHP.
Hot Spot
I'm using about the same setup, a Spectra C on a 600watt OHP. I'm also having the same problem with the hot spot. I tried the tape fix also, with about the same result. I have been thinking of trying placing a lense (I'm not sure if its a condenser or an atmosperic lense or if they are the same thing!) close to the bulb to help disperse the light more evenly. I've been looking at YWH's setup as an example. I'll do some searching tonight on this site to figure out what type of lense to use. The "hot spot" is actually where the focal point falls exactly on the element of the bulb. Somehow we've got to figure out how to diffuse that without losing the full power of the lamp....? I'll let you know if I find out anything and if you figure it out, please let me know 😀
I'm using about the same setup, a Spectra C on a 600watt OHP. I'm also having the same problem with the hot spot. I tried the tape fix also, with about the same result. I have been thinking of trying placing a lense (I'm not sure if its a condenser or an atmosperic lense or if they are the same thing!) close to the bulb to help disperse the light more evenly. I've been looking at YWH's setup as an example. I'll do some searching tonight on this site to figure out what type of lense to use. The "hot spot" is actually where the focal point falls exactly on the element of the bulb. Somehow we've got to figure out how to diffuse that without losing the full power of the lamp....? I'll let you know if I find out anything and if you figure it out, please let me know 😀
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