color balance in the pressroom

Raymond Ramirez

Well-known member
Good day guys... I have a small issue at a customers sight. We are trying to get color balance but after close inspection the lighting in the pressroom is the issue. The lighting at the press is causing a much undesired magenta shift. I need info on proper lighting or CGI. I fo for his lighting
 

gordo

Well-known member
Good day guys... I have a small issue at a customers sight. We are trying to get color balance but after close inspection the lighting in the pressroom is the issue. The lighting at the press is causing a much undesired magenta shift. I need info on proper lighting or CGI. I fo for his lighting

The ISO spec is 3664:2009 (there may be a more recent version)
Basically CIE D50, Ra value of over 90, 2000 Lux (+/- 250 Lux) in the centre area (+/- 500 on the rest of the area)

A critical issue is general shop light spillage into the viewing booth skewing the appearance.

Some shops outfit the viewing booth (or client viewing area) with standard office lights as well for an indicator as to how the color will shift in its normal viewing environment. Also, some shops include a black light to get an insight as to the relative OBA content in the proofing paper and press paper (OBAs are a major contributor metameric failure at the press).

Is that what you're asking for?
 
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Bret Hesler

Well-known member
If they have fluorescent lighting above the presses, there are a couple full-spectrum, daylight bulbs that are similar to GTI or Just Normlicht bulbs. I wouldn't recommend them for inside a viewing booth, but for the areas around the viewing booths, it goes a long way toward cutting down on the effects of the bad light hitting the sheet.

I have been using Sylvania Octron F32/T8/950 bulbs. The 950 in the code means 90+ Color Rendering Index (CRI) and D50 color temperature. They cost a bit more than cool white fluorescent bulbs, but much less than viewing booth bulbs.
 

pacart

Well-known member
If they have fluorescent lighting above the presses, there are a couple full-spectrum, daylight bulbs that are similar to GTI or Just Normlicht bulbs. I wouldn't recommend them for inside a viewing booth, but for the areas around the viewing booths, it goes a long way toward cutting down on the effects of the bad light hitting the sheet.

I have been using Sylvania Octron F32/T8/950 bulbs. The 950 in the code means 90+ Color Rendering Index (CRI) and D50 color temperature. They cost a bit more than cool white fluorescent bulbs, but much less than viewing booth bulbs.
We also use daylight bulbs in our pressroom, we don't have a viewing booth, but we do have a viewing lamp. You can get the daylight fluorescent bulbs at Home Depot or Lowes.
 

gordo

Well-known member
We also use daylight bulbs in our pressroom, we don't have a viewing booth, but we do have a viewing lamp. You can get the daylight fluorescent bulbs at Home Depot or Lowes.

I would strongly caution against using office/daylight fluorescent bulbs for evaluating press to proof alignment. That is because those bulbs have a different spectral composition than the proper ISO specified bulbs. Here's a comparison graphic: (Daylight/Daylight Fluorescent/ISO 3664:2009 Fluorescent)



Note the spectral energy peaks are in different places and that the office fluorescents have a very discontinuous spectral profile with whole spectral areas missing. Also note the UV component of the ISO bulbs (below 425nm) which is absent in the office bulbs.
 
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mihas

Member
I chose a lamps to my prepress and to my printing house by CRI and CQS (Color Rendering Index, Ra, Ra14, Ra15; Color Quality Scale (NIST), Qa, Qf, Qp, Qd-GAI). Ideal reference for daylight is all indexes CRI=100% and all indexes CQS=100%. If all indexes CRI>95 and CQS>95 - lamps suitable for color management in prepress and in print house.
 

tamale

Active member
I am currently having viewing booths custom built. Can anyone tell what kind of ballasts to use with D50 lamps? This seems to be a well guarded secret!

Tamale
 

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