I have ISCO lenses and during credits I can see a blue/purple halo around words.
This halo can be noted only if you are close to the screen.

My screen size is 36 feet long and the distance from booth is about 166 feet (if I converted from meters correctly!!).

Is it normal?

Thanks

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Most of the time, if the fringing is to the point of being objectionable, particuallary if it isnt' consistant across the entire image, (check with 35-PA and look at all the little squares), it is a lamphouse alignment issue rather than the lens....

The current crop of ISCO and Schneider lenses are really very good to the point where fringing shouldn't be noticable unless you have a lamp alignment problem...I'd look there.

Steve

If this is a "scope" lens, have you set the distance ring properly? If not, astigmatism will cause the horizontal and vertical lines to focus at different points, aggravating chromatic aberration. See the procedure for properly setting distance in the "Tips" section of Film-Tech.

If the images were good before, and now have deteriorated, what has changed? Lamphouse alignment and damage to the lens are the things to check.

BTW, sometimes there is slight color fringing around the words in credits on color prints, due to the lenses used in optical printers, or "halation" from overexposure. You should use the SMPTE 35-PA (RP 40) test film, which is a black-and-white silver image, to check for chromatic aberration.

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John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com

I've had people ask me to "fix" the picture on more than one projector. I went there and took one look at the lens. It looked like a DOG LICKED IT!

Thanks again, I will check with your suggestions and I'll let you know

Personally, I don't clean lenses all the time.
I prefer to do it on a case-by-case basis. If I see one that's dirty I clean it.

I'd rather have a couple of dust specks than have them all scratched up from poor cleaning technique.... but what I've seen in RIDICULOUS!

Usually, a dirty lens causes haze, reducing the contrast and sharpness of the image. Bright objects or titles may have a "halo" around them, and the dark areas of the scene will go "smoky". Dirt or scum on a lens would not normally cause colored fringes or a "blue/purple halo around words", which sounds more like chromatic aberration or color fringing due to halation in the printing process.

Dirty lenses are a real "contrast killer":
http://www.kodak.com/US/en/motion/newsletters/reel/december99/pytlak.shtml

I agree with you that lenses should be kept clean, but care is needed not to damage or scratch the lens surfaces by improper cleaning. Loose dust is best removed by a clean camel's hair lens brush. Fingerprints, oil droplets, scum, or dog saliva require careful use of liquid lens cleaner, being careful not to get liquid into the lens.

I guess the next question I'd ask is, "Does this occur with all prints, or in other houses with the same print?" (If it's a multiplex) After that, I'd look into lens condition and age. I'd also quickly check the "astigmatism" adjustments if it's only on the SCOPE lens. You'd be surprised to find out how many lenses I've found that have their settings all catty-wompass.

Don't worry! I understand what you mean! I can't tell you how many dirt lenses I've saw...

Bye

Projecting oily prints may vaporize some of the oil, leaving an oily "scum" on the rear element of the lens, which will cause haze and degrade contrast. If so, careful cleaning of the lens with lens cleaner is called for.

------------------
John P. Pytlak, Senior Technical Specialist
Worldwide Technical Services, Entertainment Imaging
Eastman Kodak Company
Research Labs, Building 69, Room 7419
Rochester, New York, 14650-1922 USA
Tel: 716-477-5325 Fax: 716-722-7243
E-Mail: john.pytlak@kodak.com