Monitor brightness issue

[Steve Moore-Vale]

Hi. I have been spending quite some time today trying to calibrate my monitor correctly, mainly for photography work. I am now satisfied that my colour and contrast are correct. However, when setting my brightness level, I decided to go with what seemed like a general photography standard of 120cd/m2 but when I did the calibration using my Spyder 4 colorimeter it told me that with 120 set on the monitor it was actually measuring over 130. To get the readout from the colorimeter to be 120 I had to lower it on the monitor to 106. I know monitors are supposed to lose brightness over time but this one seems to be gaining brightness. Has anyone had this before? Colorimeter measurement issue perhaps? The monitor is an eizo coloredge cs230 and quote old now. I have had it for several years. Is there another method I can use to verify what the brightness actually is? I do have an old spyder colorimeter I could install that may be able to provide a ‘second opinion’. 

[BobVonBob]

Are you sure the monitor's brightness values were ever correct to begin with? If you're able try the brightness measurement in a totally dark room and see if that changes your values. Perhaps you were getting some light bleed from the environment, assuming you weren't already doing this.

[Steve Moore-Vale]

Thanks for your reply. I can try it in a completely dark room but I deliberately calibrated in an environment that matched what I would be working in normally. I made sure there was no obvious intense light falling onto the monitor but of course I can’t be entirely sure what light it was seeing other than the monitors own backlight it was measuring. 

[Steve Moore-Vale]

I may be over thinking this but I’ve had an idea to test this and I wonder whether you think it may work. I have another monitor in the loft. I am able to connect both monitors to my pc so if I connect them both and set the other one to 120cd/m and then use my cameras exposure meter to take a reading off my existing monitor (making sure it is exposed correctly) and then move it over to the other monitor, my cameras light meter should tell me if the second monitor is brighter, darker or the same. And I would do it in a dark room. Would that work as a test?

 

EDIT:

I tried it and they matched. I took an exposure reading from my second monitor after I set it to 120cd/m. using manual mode I got the exposure meter to dead centre whilst pointing my camera at a blank word document (nice white background).  I then switched to my main monitor and repeated the test and both exposures on the white word document were an exact match.