For those of you who are using an x-rite EyeOne Display 2 (or LT), I recently asked a few questions to Spectracal as I had a few teething problems when installing Calman 3.2 and Derek has sent me some really useful information, which I though I would share with you.
As I didn't experience an immediate and obvious improvement when I first used Calman, I expressed my concerns regarding low light readings and the lack repeatability when working on the greyscale with the i1, and asked whether reading from the PJ would help or not.
I'll split the info in Calman specific and non Calman specific, so that HCFR users are not confused:
Non Calman Specific:
1) Regarding accuracy in low light, in Derek's experience, the diffuser on the i1 (which you have to use when reading directly from the PJ and not off the screen) is not very accurate. Also in his opinion the i1 is accurate enough in low light to be able to read fine from the screen. So his advice is read from the screen rather than the PJ, with the i1 it's the best thing to do.
2) Regarding the repeatability issue, Derek said that "
The D2 can be sensitive to placement. If you look on the bottom you will see 4 sensors. If one of those sensors is seeing a pixel structure or shadow and not seeing the same light as the others and you will get different light. One way around this is to pull the D2 back a bit more or try a different position". I found this very interesting, and had definitely not noticed/paid attention to this. I will be more careful in the future that I am no too close to the screen, as it may help (my tripod had the i1 about 2-3 inchs from the screen). I did try to find the best orientation to maximise fL at the beginning of each session, but I will try in the future to be sligthly off-axis to make sure that when I aim at the centre of the window, the shadow can't be in the sensors window at all.
Calman specific:
1) I was wondering why the "low trigger" function was not available when the i1 is used. Derek explained that
"the low trigger for the Display2 is not necessary, it has an exposure control so you can set the exposure from 0.5 to 4 seconds. In testing we have found 1.5 to be a good exposure time. You can extend it to 2-3 seconds if you like but the accuracy will be about the same. As for the low light handler in HCFR all they do it take multiple readings and a simple average because they don't have access to the exposure control like we do".
The following are just a few additional notes/tips from me, so take them with the usual pinch of salt
.
HCFR Specific:
1) Regarding Derek's statement above in case you've missed it in my last list of tips, selecting "average many reads on dark measurements" (in Measures/sensor/configure) greatly improves HCFR's accuracy and repeatability at 0-30 IRE, at a very reasonable cost of speed. I didn't have time to compare with Calman's method yet, but I'll let you know because one of the main reasons why I bought Calman was to see if a different handling of the hardware would save me buying an i1 pro right now. I do plan to buy an i1 pro at a later stage (when my i1 will start to drift), and plan to train the i1 to the i1 pro to get the best of both worlds (speed and accuracy), so I will need both licenses anyway.
2) I have also realised that if you don't check "use gamma reference to compute greyscale dE" (in Advanced /Preferences/Advanced), well, you imagine the consequence: you think your greyscale is great but in fact your luminance can be quite off the gamma value you are targetting at each IRE level, even if you average gamma is spot on, which is related to my earlier post re gamma.
So to summarise past tips with recent ones, in order to maximise the accuracy/repeatibility of the i1, I am doing the following:
- Always give at least 15-20mn for the lamp to warm up before starting measurements (standard practice)
- Measure off the screen - rather than off the PJ with the diffuser - as it seems preferable with this meter (apart from the fact that doing so takes the screen into account, which is of course generally preferable)
- Set the i1 slightly off-axis on its tripod when pointing at the centre of the window to make sure no shadow can affect one of the four sensors.
- Make sure I set the iris of the 750 at the same setting if I plan to compare with previous measurements (if you need proof of this, close/open the iris while you are doing a continuous reading, and you'll see the RGB values drifting accordingly. Not by much, but enough to make a difference when reading a greyscale).
And, if using HCFR:
- Check the "average many reads on dark measurements" (to improve low light accuracy)
- Check the "use gamma reference to compute greyscale dE" (to make sure my dE reflect gamma as well as RGB)
Again, apologies if this is obvious to everyone, it definitely wasn't to me
... As usual, comments and corrections if your experience is similar/different are welcome.
I plan to work on my greyscale targetting a 2.2 gamma (although I like the deeper black levels I get with 2.3, I lose too much detail to my taste in dark scenes), so I'll keep you posted if I see any improvement using this methodology, and also re using Calman versus HCFR.