Contact printing issues

James Drukeli

Member
Joined
Feb 25, 2019
Messages
31
Location
Japan
Format
8x10 Format
I'm contact printing film to film to make a positive. The film is rather small 3.5 x 2 (business card), and my problem is that the printed positive always seems to be slightly smaller than the original. As in, the lines and dots are always a little narrower than the original. I'm exposing for 2 seconds with a .05 watt led night light. The result is crisp and clear, just a little smaller than it should be.

Would increasing the exposure time with the 0.5 led help? Or is it a developing issue?

Will experiment again next weekend but I'm just trying to get any advice before I get back into it.
 

NedL

Subscriber
Joined
Aug 23, 2012
Messages
3,388
Location
Sonoma County, California
Format
Multi Format
I don't have a clear understanding of the problem. Are the lines and dots supposed to be black on the positive?
Ensure good contact between the film, and perhaps try a longer exposure with your led light source at least 2 meters away....
 
OP
OP

James Drukeli

Member
Joined
Feb 25, 2019
Messages
31
Location
Japan
Format
8x10 Format
NedL said:
I don't have a clear understanding of the problem. Are the lines and dots supposed to be black on the positive?
Ensure good contact between the film, and perhaps try a longer exposure with your led light source at least 2 meters away....
Click to expand...

Contact is good, yes it's litho film so solid black. I'm saying the dots and line are a little smaller on the print. For instance if a circle on the original negative is 1mm in diamter, on the print positive it's .80mm in diameter.

Okay, I'll try exposing a little longer.
 

NedL

Subscriber
Joined
Aug 23, 2012
Messages
3,388
Location
Sonoma County, California
Format
Multi Format
If a point light source is close enough, the thickness of the gelatin on the negative can have a small effect. I thought perhaps you were describing something very subtle. A change from 1mm to 0.8mm is way too much to be due to the height of the light source. I'm not sure what is going on, usually when a contact print is made emulsion to emulsion as Andrew suggested, it is extremely close to a perfect copy.
 
OP
OP

James Drukeli

Member
Joined
Feb 25, 2019
Messages
31
Location
Japan
Format
8x10 Format

I just used that as an example so you could understand what I'm referring to. the actual size differential is like .008mm you need a magnifying glass to see it but it's definitely there.
 

NedL

Subscriber
Joined
Aug 23, 2012
Messages
3,388
Location
Sonoma County, California
Format
Multi Format
I see. If the LED nightlight is diffuse ( not a point source ), and especially if it can bounce off a nearby wall or somehow hit the film from more than one direction, it's just possible it could have that much effect.
 
OP
OP

James Drukeli

Member
Joined
Feb 25, 2019
Messages
31
Location
Japan
Format
8x10 Format
NedL said:
I see. If the LED nightlight is diffuse ( not a point source ), and especially if it can bounce off a nearby wall or somehow hit the film from more than one direction, it's just possible it could have that much effect.
Click to expand...

So you're saying that reflections and/or the diffusion cover on the night light might be causing this effect? Would it be better to take the cover off the night light and expose the diode?
 

silveror0

Member
Joined
Dec 3, 2007
Messages
364
Location
Seattle area, WA
Format
Large Format
Gotta hunch you're seeing the effects of refraction in the two extremely thin emulsion layers in contact with each other. The fact that the antihalation layer is no longer present on the original, but still present on the copy during exposure may possibly influence the effect. Obviously, increasing the distance of the LED from the sandwich will reduce the magnitude of refraction angles of incidence and should help. In addition to raising the LED (suggest about 6 ft.), removing the diffuser from the light source should approach a point source as well as help with needed increase in exposure time. A stronger LED might be needed at the greater height should reciprocity rear its ugly head.
 
Last edited:

NedL

Subscriber
Joined
Aug 23, 2012
Messages
3,388
Location
Sonoma County, California
Format
Multi Format
Yes, I agree. If you can make it more of a point source and make it higher, that might help. And not too close to a light colored wall.
It will be interesting to hear if this helps... I'm not so sure. With such a small negative, I would have thought that 24 inches would be high enough.
 

laser

Advertiser
Advertiser
Joined
Jun 16, 2005
Messages
1,051
Format
4x5 Format
I expect you are under exposing. Run an exposure series at 1/2 stop increments.
 

koraks

Moderator
Moderator
Joined
Nov 29, 2018
Messages
22,624
Location
Europe
Format
Multi Format
Did you use fb paper and did you measure the difference after drying the print? Fb paper shrinks a bit upon drying. Perhaps it even ends up a little smaller than when you take it out of the box. I never did measurements on this, but this is the first thing that occurs to me.

If it were a problem with a point source close to the paper, the resulting print would end up marginally larger towards the edges of the print, but likely not visibly so.
If it were a problem with a diffuse light source, the print would possibly not be tack sharp, but again, given good contact between film and paper during exposure, this is unlikely to be visible - and it won't affect actual image size.
 

Kino

Subscriber
Joined
Jan 20, 2006
Messages
7,755
Location
Orange, Virginia
Format
Multi Format


Image spread happens when you print motion picture sound tracks (optical, variable area) and the spread is what can cause distortion. This sounds like what you are experiencing .

Go here: https://www.kodak.com/uploadedfiles/motion/US_plugins_acrobat_en_motion_support_h44_h44.pdf and read page 4 for an idea of how it works.

It can be a very tiny exposure difference that is causing the image to spread.

I know you are not recording optical sound, but the principals should be the same for high contrast images...
 
You must log in or register to reply here.
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…