First iMac calibration impressions...

Started Aug 10, 2007 | Discussions thread
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uwe_r Veteran Member • Posts: 3,429
First iMac calibration impressions...

OK, so I had my three hours of testing today... quite an experience

What was used:

  • shop provided two iMacs (20" 2.4GHz, 320GB HD, 2GB RAM, HD 2600 PRO and 24" 2.4GHz, 320GB HD, 4GB RAM, HD 2600 PRO) - both machines were on for hours, so they were properly warmed up

  • I brought along images, Epson R2400 printer, Hahnemuehle Digital Fine Art paper and respective ICC profiles

  • Spyder 2 Pro colorimeter and software, EyeOne Display 2 colorimeter with Match software, Xrite DTP-94 colorimeter with ColorEyes software

  • targets set to 2.2 / 6500K / 120 cd/m2 in all tests

The first observation was that, depending on your ambient lighting, following the recommendation of profiling/calibrating in the same conditions the display will be used in may not be possible at all. I set both displays to a "normal" location (no direct light, but some ceiling light and little stray light from a window some 12 feet / 4 meters away - it was a rainy day, so window light was not bright). It was simply impossible to get consistent results, as the glass front seems to suck in and reflect light from everywhere. I did three runs each using all calibration packages, without moving the displays or changing ambient light the calibration results differed greatly, resulting in all kinds of hues - the ColorEyes package scored best (as usual) as it seems to eliminate more errors by taking more samples (also takes longer), but off is off... no printing was done, as it was obviously not making any sense.

Then we moved both machines to a back office with no windows and only a dimmed daylight coloured ceiling lamp. This made a big difference. Doing the same three runs on each machine gave consistent results with the ColorVision and ColorEyes packages - the EyeOne still failed to produce consistent results, but the differences were minor and no more hues / obvious errors.

Then the test was repeated in complete darkness - now all three packages gave consistent results without obvious errors.

So - calibrating/profiling at all was done, and pretty much what I had expected. Next question was the calibration quality. I cannot list each and every detail, because it will take forever - so only a quick summary:

Using the profiles generated in the last run getting truthful colours and matching prints from sRGB images was no problem with both iMacs - that can be easily translated into: for consumer and most prosumer use the machines are fully up to the task.

20" model

For professional (pre-press, wider gamut colour space photo editing, fine art printing, video editing for reverse telecine, etc.) graphics use the 20" is clearly out without using an external display - aRGB files do not display with all colours, there is dithering going on in colour gradients, blocking in grey gradients and there is quite some black clipping. It is more like a very good laptop display with the usual results: sRGB files print quite accurately - shadow detail can be a little unpredictable, no other quirks, luminance adjustment works fine and there are no significant colour shifts when adjusting brightness, viewing from an angle is limited, but not an issue for normal use as a main display. The ColorEyes package worked best (mainly best gradients and least black clipping), the Spyder was just fine - the EyeOne software produced the worst grey-scale gradients and most black clipping.

24" model

Better, but not great and clearly worse than the previous 24" model, cannot compare to the 23" ACD. aRGB images displayed more accurately, gradients were a lot smoother, but still far from the ACD or the previous 24" model; black clipping does occur, but is significantly less than with the 20" model - for most people using standard printer profiles or consumer print services it should be absolutely irrelevant. I did four test prints on fine art paper (one sRGB and three aRGB files, one of them grayscale) - the sRGB file was very good (only very minor differences in dark shadows - I had to look extremely hard to even detect it), one aRGB file came out great (but contained mainly red and green), there was a problem with the second one (colour shifts in some purple tones - I have to verify this, could be a driver issue - think I have seen that before), the grayscale print was a bit of a let down though - the black clipping becomes more obvious here. Luminance adjustment and viewing angles were fine with the 24" model. The recommendation for calibration devices is the same as for the 20" model, but the EyeOne had far less problems with the 24" model - it compared well to the Spyder, but both were behind the ColorEyes package with gradients.

The performance of both machines is great - the Santa Rosa chipset does seem to make a huge difference with memory access, felt performance is some 30-40% over the previous model with some tasks. I personally cannot stand the keyboard - it has a nice weight and does not move around on the table, but the keys feel like jelly with no feedback whatsoever, the positioning of the F-keys is terrible, the white caps do not match anything on the iMac (who designed this?) - will keep my tactile pro.

Hope some of the above is helpful.

Cheers,
Uwe

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