A question on projection brightness

[Mike Buckles]

This can apply to super 8 as well, but I was having a concern with projecting my slides. I noticed that my slides are not quite as bright and colorful when I project them as they are in my little handheld viewer. (particularly Kodachrome)...the colors are duller. I posted this question on the Pop Photography forum, and one of the members had this to say: <BLOCKQUOTE><font size=2 face="verdana, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="verdana, sans-serif"> </font></td></tr></table></td></tr></table></BLOCKQUOTE>--------------------------------------------------------------------------------
The brighter lamp will certainly make your projected slides brighter, at the cost of greater heat and greater damage to the image over time. While Kodachrome has a greater life than E-6 films in archival storage, it actually degrades more quickly under the intense light of a projector.
I suggest you first look at your reflective surface. A wall is your worst choice, because even a wall painted in flat titanium white has less reflectance than any projection screen. And how often will your wife let you paint a wall dead flat white?

I haven't looked at screens in a long time so the following may be outmoded. When I was looking at screens, there were three basic surfaces: flat (or matte), glass bead, and silver lenticular. Flat gave the sharpest image and widest viewing angle, but the least reflectance of the three. Silver lenticular gave the brightest image if you were close to the projector axis. If you moved more than 10 - 15 degrees off-axis brightness fell off quickly. It also gave the worst sharpness because it was composed of small vertical reflective silver lines. Kinda like projecting your slides on a TV. Glass bead was a good compromise -- brightness almost as good as silver lenticular, a usefully wide viewing angle, and sharpness almost as good as flat.

So what kind of screen do you have? I'd think about upgrading that first.

Lenses: the f/2.8 is 2/3 stop faster than the f/3.5, so yes it will deliver more light to the screen. Focal length depends on your needs. Which part of zoom range do you mostly use now? Get the prime lens closest to that
<BLOCKQUOTE><font size=2 face="verdana, sans-serif">quote:</font><table border="0" width="90%" bgcolor="#333333" cellspacing="1" cellpadding="0"><tr><td width="100%"><table border="0" width="100%" cellspacing="0" cellpadding="2" bgcolor="#FF9900"><tr><td width="100%" bgcolor="#DDDDDD"><font size=2 face="verdana, sans-serif"> </font></td></tr></table></td></tr></table></BLOCKQUOTE>

My super 8 films (conceivably) would also be experiencing a darker look, depending on the lens on my projector, bulb used, etc. I know the moderator shoots slides a bit, does getting the brighter bulb really increase the damage to the slides that much? I really don't leave the slides up on the screen that long (no rotoscoping on the walls!) Or would the combination of the larger lens and using a screen make that much of a difference without using the brighter bulb...or all three? Also, as far as a screen goes, it looks like glass bead would give me the best options for brightness/sharpness...I'm only projecting in the livingroom, not a large place. I assume a screen that makes my slides look better/brighter would also help my super 8.

[Alex]

The brighter the bulb, the bigger the fan needed to keep the fan and the slide cooler.

Besides technical issues, there are psychological issue to contend with.

Do you have an actual screening area that can go completely dark and that is comprised of a big screen with no distractions on either side of the screen?

Part of what makes an image looks bright is the absence of distractions around the image. Also, if you use a screen and keep it away from the wall, the extra distance to the back of the wall acts as a subliminal barrier that draws the eye back to the screen, making it appear brighter.

[Mike Buckles]

You bring up an interesting point that I hadn't considered. There are things on the sides of the wall where I'm projecting...if I did use a screen, it would be separated from the wall. The brighter bulb is recommended by Kodak for use in this projector.

[Mike Buckles]

Has anyone used a 35mm projector lens before? (movie or slide) It seems to me that the closer the projector is to the screen, the brighter the image would be...right now I'm using a 70-120mm zoom lens for my slide projector, f 3.5. The 35mm lens is a fixed focus f 2.8. I've also heard that the fixed focus lenses are supposed to be a bit sharper, and while the zoom lens I have has plastic elements, the fixed focus is made of glass. It wouldn't bother me that the projector would have to be closer to the screen to get the same 6 ft image...I only project in livingrooms, so as long as the projector isn't blocking the screen, no problem.

[Mike Buckles]

Upon checking my Bolex sp8, it has a zoom lens 17mm-30mm, f 1.3. curious how all my movie projectors have zoom lenses right around this range, but most of the zoom slide projector lenses are usually 70mm and up. Is this due to the larger format of 35mm slide film? When placing my movie projector about 12ft away from the wall, it produced a picture about 4 ft wide diagonally. Would a 36mm f 2.8 slide projector lens produce different ratios, because the lens is larger, even though the 36mm is similar in mm size to the 30mm bolex super 8 lens?

[Alex]

The "ratio's" as I understand them are... a "normal" lens in 35mm is 50mm, in 16mm it's 25mm, in Super-8mm it's approximately 12mm.

Perhaps that correlates with being able to slit 35mm into (4) Super-8mm films or (2) 16mm films.

[Mike Buckles]

Yes, you're right, the different size format must account for the lens size differences. Anyhoo, I decided when I have the $$$ to go for a 93mm f 2.5 lens..should brighten up my Kodachrome's sufficiently without having to go to a stronger bulb. I really do love projecting my super 8 and slides. I discovered darker backgrounds look best projected on super 8..hides the dirt and scratches so well! Like outdoors on a green lawn...looks really good!