Re: Monitor Calibration
Re: Monitor Calibration
- Subject: Re: Monitor Calibration
- From: Robin Myers <email@hidden>
- Date: Fri, 13 Nov 2009 19:34:48 -0800
Everyone is right for different reasons. Colorimeters are more accurate and spectrometers are more accurate, depending on the situation.
The colorimeter sensors are huge compared to the size of a spectral band sensor in a spectrometer. The large size gives the sensor a much better response for low light measurements, increasing the signal to noise ratio (SNR), as noted by Karl on page 4 in his paper. So the advantage goes to the colorimeter for low light measurements.
Just to be clear, low light measurements relate not only to measuring the display's black point, but to all the darker portions of the display's tonal reproduction curves. This is an image's shadow detail.
The bad news with colorimeters is that they have to be calibrated for a particular display technology. Karl mentions on page 5 that a single calibration matrix will suffice for most CRT displays, but this matrix needs to be different for LCD panels. He then mentions that forthcoming LCD panels will require a third calibration matrix. We do not have a creation date on this paper, but it would be fair to assume that this third matrix is already needed, and possibly more.
Just considering backlight technologies will show that more matrices are needed. There are fluorescent, white LED, and red/green/blue LED backlights being used in LCD panels. When thrown in with organic LED (OLED) and plasma displays, there are lots of matrices needed to have a single colorimeter work with any display technology.
It might be worth mentioning here that colorimeters designed for displays (e.g. i1 Display, Spyder) can make only emissive light measurements. Although some have been designed to also measure display projectors. Display colorimeters must also be replaced when they are no longer able to be adapted to newer display technologies.
Although the spectrometer has a lower signal to noise ratio for low light measurements, they do not need to be tuned for different display technologies. If the colorimeter is mismatched for the display technology being measured, it can result in very disappointing monitor calibrations and ICC profiles. The improved light sensitivity will not help if the overall quality suffers. A spectrometer can give a more accurate result in this situation.
There are also some spectrometers that improve their low light SNR by increasing the measurement time for low light levels. Even some of the high end spectroradiometers increase their measurement time for low light situations.
Spectrometers are more expensive than colorimeters, so their cost must be compared against their benefits. In addition to being able to stay current as display technologies change, they can be used to measure materials from other devices such as printers. Some spectrometers can measure displays, ambient light, photo flashes, display projectors, printer output and transparencies. So the flexibility advantage goes to the spectrometer.
To summarize the two devices:
Colorimeter
Pros: More accurate for low light measurements when tuned to the display technology.
Low cost.
Cons: Limited by the number of calibrations to specific display technologies.
May require replacement as display technologies change.
Measures emissive light only.
Spectrometer
Pros: More flexible, not tuned to specific display technologies.
May be used for measuring other technologies such as prints, transparencies, etc.
Cons: Less accurate low light measurements.
More expensive than display colorimeters.
-----------
Here are some ideas to help with the decision.
1. If you have a display with a matched colorimeter and software, use it.
2. If you have an older colorimeter with newer, different technologies than the colorimeter was designed for, check if the colorimeter can be updated with new calibrations for the newer displays. Otherwise, get a new colorimeter or switch to a spectrometer.
3. If you have a newer colorimeter and older display technologies for which the colorimeter is not calibrated, change the colorimeter calibrations (if possible), change to newer displays, or use a spectrometer.
4. If you have a mixed set of display technologies, requiring more calibrations than the colorimeter can accommodate, use a spectrometer.
5. If you need one measurement device for any display technology, use a spectrometer.
6. If the highest quality results are desired and cost is no problem, use a tuned colorimeter for each display technology and a spectrometer for everything else. Be aware that you may have to purchase a new colorimeter every few years as display technologies evolve.
It comes down to a tradeoff between accuracy in low light measurements, cost and flexibility. Clear as mud?
Robin Myers
On Nov 13, 2009, at 5:39 PM, Marco Ugolini wrote:
> In a message dated 11/13/09 5:30 PM, Andrew Rodney wrote:
>
>>
>> On Nov 13, 2009, at 6:23 PM, Marco Ugolini wrote:
>>
>>> I'd really be delighted to hear the frank opinion of other color scientists
>>> on this forum (Robin Myers? Harold Boll? etc.), so that we don't keep
>>> hearing just Karl Lang's opinion again and again regarding the declared
>>> "limitations" of spectrophotometers in monitor calibration and profiling,
>>> after having heard it many times already. <g>
>>
>> Its not just Karl’s, its X-Rites considering the source of the paper...
>
> Andrew,
>
> As I said, I just think it'd be interesting to hear from other color
> scientists who have kept silent so far.
>
> Marco
>
>
> _______________________________________________
> Do not post admin requests to the list. They will be ignored.
> Colorsync-users mailing list (email@hidden)
> Help/Unsubscribe/Update your Subscription:
>
> This email sent to email@hidden
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
Colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden