Glassless or glass neg carriers?

[artonic]

...What is the curvature of field for enlarging lenses...

I thought that enlarging lenses were flat-field, i.e. with no curvature?

 

[David A. Goldfarb]

"Flat field" usually means "relatively flat within a certain range of magnification," and enlarging lenses are designed to fit that description for typical use (or sometimes special use in the case of lenses like the Rodagon G lenses for mural sized enlargements).

 

[Lee Shively]

I guess we're hijacking the thread so I apologize but I also now have a question concerning glass carriers.

In my previous experience with Leitz enlargers , the negative carriers were open at the bottom with an ANR glass ring at the top and they held the negatives very flat. The universal LPL carrier (for 35mm thru 6x7) I just bought has glass on both the top and bottom. I'm wondering if the bottom piece of glass is necessary?

 

[Jon Shiu]

I guess we're hijacking the thread so I apologize but I also now have a question concerning glass carriers.

In my previous experience with Leitz enlargers , the negative carriers were open at the bottom with an ANR glass ring at the top and they held the negatives very flat. The universal LPL carrier (for 35mm thru 6x7) I just bought has glass on both the top and bottom. I'm wondering if the bottom piece of glass is necessary?

Hi, the glass is necessary to prevent the negative from falling through the neg carrier.

Jon

Alright, the bottom glass is necessary to support the film, otherwise it will sag. I didn't mean completely fall through.

 

[Lee Shively]

Not really. The masking blades would prevent this. Also, negative strips extend into the metal frame area where they are also held in place.

 

[donbga]

Not really. The masking blades would prevent this. Also, negative strips extend into the metal frame area where they are also held in place.

The glass negative carrier for Saunders LPL enlarger needs both pieces of glass to function properly. The maksing blades provide not support for the negative.

 

[jstraw]

I presumed that while the top, AN glass was important for preventing Newton rings, the bottom glass (for sheet film) was important because for sheet film, sag is the problem, not curl. Is this correct?