SWOP Hi Lo References

[cmcfarling]

I realize that the lastest SWOP spec (11th edition) has moved away from SID/TVI in favor of G7. However in an effort to understand the history of SWOP I'm trying to make sense of how the v10 spec specifies densities. There's a ton of info that states how SWOP refers to the Hi Lo References in regard to target densities, but I haven't found any good explanation as to the how and why of it.

The Hi Lo References are something that must be purchased I know. This is available as a one time purchase or a subscription. Why would one need a subscription to this information? Once purchased, what exactly do you get, is it just a single piece of paper with two patches for each color (CMYK), or is there more to it? Why did SWOP choose this route over just specifying target ink densities? Does/did anyone actually use this Hi Lo Reference data or did everyone just accept that the historical averages reference in the SWOP v10 FAQ were the numbers to shoot for? Those being:
C 1.30
M 1.40
Y 1.00
K 1.60

 

[gordo]

Why did SWOP choose this route over just specifying target ink densities?

By providing a Hi/Lo density sample, it wouldn't matter whether the instruments used at different print facilities were calibrated or not or whether they were set to the correct Status or not. Whatever density reading that an individual printer got when measuring the Hi/Lo patches became the Hi/Lo target density values for the presses at that shop.

best, gordon p

 

[cmcfarling]

So the whole point of having the Hi Lo Reference was to account for variations in densitometers. Interesting. For some reason that tidbit of info doesn't appear to be included in any documentation that I can find.

With that line of thinking, why not base current generation LAB values on a Hi-Lo system as well? I'm not proposing that that should be the case, in fact it would be quite terrible if it were I think. ButitI would stand to reason that spectrophotometers from various shops/manufacturers/etc will vary in the LAB values that they read. Different instrument, same issues.

Did the powers that be decide that the Hi-Lo system was outdated?

 

[gordo]

The reason for the Hi Lo Reference was to account for variations in densitometers is alluded to in the old SWOP books where it is stated: "Note: Actual density ranges will vary depending on the densitometer used to read the SWOP Hi-Lo Color References." I confirmed the reason I provided when I was in the Idealliance Group. Also, it does make sense.

I personally don't know, but I would speculate that "the powers that be" decided that the Hi-Lo system was outdated when SWOP adopted the G7 methodology.

At one time Idealliance was going to sell reference GRACoL 7 kits with press sheets so that printers would have a certified physical reference target to use for their color calibration. But that seems to have been abandoned (I wonder why?).

Remember also that although SWOP, after 1986, included guidelines for web printing of publications it was created as specifications for the input of files - not output of those files. I believe that it still adheres to that mandate, although it's a bit fuzzy (for me) with their adoption of G7 methodology.

best, gordo

 

[cmcfarling]

Thanks for the insight. Those calibration kits are in fact available btw

G7 Calibration Kits

 

[gordo]

Thanks for the insight. Those calibration kits are in fact available btw
G7 Calibration Kits

Ahhh, thanks for the link. I went looking for it in the wrong place (idealliance) - there was no cross reference.

best, gordo

 

[jlind]

Don't forget that the Hi-Lo patches were specifically used to establish upper and lower inking levels for press proofing of national ads at multiple locations. It was and is a laborious process to print and inspect in quality for the Hi-Lo patches.

Off-Press proofing manufacturers used those patches as colorimetric and densitometric aimpoints for their Cromalins, MatchPrints, ColorArts, Iris, etc. At the same time it spawned an ink verification program at GATF to make sure the printing inks weren't too far off shade from the Hi-Lo references.

This led to the SWOP Off Press Proof Certification Program, where colorimetric and densitometric aimpoints were allowed to float in lieu of a Perceptual Color Match to an offset sheet printed to SWOP standards. This is how an ink jet Epson and a Cinema Soft Proof can get SWOP certified. Once there was a visual match, according to "the powers and experts that be", the correct densities and colorimetric values for each proofing system was whatever it was when there was an agreed visual match.

This all happened state side, while the ISO meetings were going on in Europe and Japan. To a certain extent, they were all rolled into one. All were emulating a finely tuned offset printing system on a given paper surface, and they weren't that different at the end of the day. Just a lot of meetings and political jostling.

There is a LAB ref, also sold by IDEAlliance. Not a hi-lo, but a laminated rugged hitching post.

Certified press sheets were always a committee dream to sell, but the market was small and the price was steep. Very hard to print a sheet filled with targets and have them all be at ANY specification, let alone an ambitious plus or minus amount.

More history than you might have wanted, take what you want and leave the rest.

John Lind
Cranberry Township, PA
724-776-4718

 

[meddington]

Thanks for the insight. Those calibration kits are in fact available btw

G7 Calibration Kits

Note that the cal kits include hard copy certified proofs produced by the manufacturer of your choice, but not in fact press sheets, which would be difficult to produce per the reasons jlind mentioned. I don't think there's been an effort to produce reference press sheets since DTR004, which included some poor samples if I recall correctly.