I found no difference between v2 and v4. I was told to use v4. I was wondering why do some people insist v2 is better?
V4 printer profiles offer advantages over V2. The white point of the print media is more completely defined and black points are no longer a free-for-all. Perceptual rendering is improved because the dynamic range and gamut of the reference is also defined. There are other differences but none that particularly pertain to print.
At least that's the theory. In practice, the implementation is left up to the profile manufacturer. V4 adds complications with black points and how the profile connection space (PCS) is encoded. Gamut mapping between profiles becomes a chained process. Each transformation creates some level of error. If all profiles in the chain are created by the same profiling software, the calculated transforms usually behave the same. Otherwise the errors can compound, leading to undesirable behavior.
We have seen this on multiple occasions with our customers who use V4 display profiles. The commonality here is a combination of OSX and Adobe software. If a V4 monitor profile is in use, Adobe products sometimes give inaccurate soft proofs when the Adobe CMM is selected. Switching to the Apple CMM or a V2 monitor profile and everything behaves properly.
V4 profiles also incorporate the Perceptual Reference Medium Gamut (PRMG). V2 profiles typically assume a print with an infinite gamut and perfect reflectivity. The PRMG is based on the P2 viewing condition - 500 lux - and a dynamic range of 288:1 with specified white and black reflectance values and color gamut. In general this is a good approach. If your printer has a very wide gamut (e.g. Epsons on good gloss stock) there can be a gamut expansion at print time; i.e. printer colors exceeding the PRMG reproduce more saturated than the soft proof shows.
For camera profiles, V4 is the way to go. LUT tables can be encoded as floating point numbers, allowing significantly more precision for huge gamut color spaces.
I am still stumped. Maybe the solution really is to light up the print more, and lower the brightness on the monitor.
No reason to be stumped - from what you say above you seem to have solved your problem by lowering the monitor brightness. Once you lower the monitor brightness sufficiently, you will automatically be adjusting the tones of the photo so that they emerge correctly from the printer. Maybe a bit of trial and error to get the monitor brightness just right, but if you adjust within a range of 90 to 120, you won't need more than several attempts to get it right, but use a proper printer evaluation test image to do this, not any arbitrary photo.
Be careful when lowering monitor brightness. Some panels perform well at levels below 120-130 cd/m2, most do not. Pay very close attention to black level definition when lowering brightness below 130. A simple step wedge works or you can view a black level check such as
on our web site. If you can reduce brightness to where your prints match the screen without compromising on-screen viewing, great. If not either increase the monitor brightness and make the necessary visual compensation or increase the light level in your viewing area.