Monitor differences - DPChallenge Forums

01/31/2005 01:51:50 PM · #1

I read in someone's comments about their picture, that while the picture looked well on a cathode ray tube monitor, that it did not on a liquid crystal display. I wondered why at the time, but did not pursue the question.

Now, I am wondering about phosphors. CRTs bombard phosphors with electrons exciting the phosphors to glow for a certain length of time, until they are again bombarded by another sweep of the electron gun. I do not know how liquid crystals work, but I had assumed it was again a phosphor excitation. Have I been right in that assumption?

In any event, as phosphors glow for varying short durations, and their glow is based on their past excitation, which is influenced by the past excitation of their neighbors, a picture should vary in appearance over time when displayed on a CRT. This is especially true when the picture is more blurry and the eye has no fixed outlines to hold context from one sweep of the electron gun to the next.

This effect should vary also between CRT monitors, with one displaying a varying glow more easily than another. But, is there a radical difference in this effect between CRT and LCD? As I do not have access to an LCD monitor to check my pictures out, how can I guess or know what they will look like on an LCD monitor?

We have standards for Gamma to determine brightness and standards for color management. Are there standards for glow decay management?

Message edited by author 2005-01-31 13:55:27.

hopper

Canon EOS-80D

Canon EF 35mm f/2 IS USM

01/31/2005 01:56:20 PM · #2

while most of what you just said is lost on me ... i will say that photos look different on each type of monitor. there's not too much you can do about it (as far as i know).

which is why the more voters that vote, the better the odds are that you've been able to show what you were trying to show (or the better the odds are that you'll realize your own monitor is way off :)

Nikon AF-S DX Zoom-Nikkor 17-55mm f/2.8G IF-ED

01/31/2005 02:36:34 PM · #3

I think that I was barking up the wrong tree. Monitor refresh rates probably have more to do with the steadiness of a picture than do variations in phosphor decay rates.

I just realized that the phenomenon that I was trying to understand in looking at some blurry pictures was more easily explained by image retention in the retina, rather than image retention on the monitor, as they occurred only when I moved my eyes. If you look at an image for awhile, it forms an impression on your retina, so that if you then look at a blank area, you will see the inverse image of the earlier image.

I also thought of interference effects such as moire patterns, but that did not seem to be the cause again because the effects occurred with my motion, but you cannot move to change moire.

So, I have contented myself as to why I sometimes see a varying glow in pictures. It seems it has to do with retention of images on my retina as I look from place to place within an image. Of course, this is enhanced by bright, blurry images and is similar to the glow I observe when looking at lights.

I still do not know what kind of differences exist between LCD and CRT monitors in terms of how pictures may look differently. Clues anyone?

cghubbell

Nikon D300

01/31/2005 03:05:21 PM · #4

Originally posted by whagerbaumer:

I still do not know what kind of differences exist between LCD and CRT monitors in terms of how pictures may look differently. Clues anyone?

LCDs tend to have a lower gamut and higher contrast. Of course, there's a BIG specturm in both LCD and CRT, so truly categorizing the differences is pretty tough these days. You'd have to compare high end to high end, etc.

I think most of what people need to worry about is calibrating to that gamma band at the bottom of all the challenge voting screens. Get your screen showing all those colors and you'll have amuch better time viewing photos than worrying about LCD vs. CRT.

Nikon AF Nikkor 50mm f/1.8D

01/31/2005 03:33:01 PM · #5

Thanks, CG. Gamut refers to the colors displayed. So, one monitor will display a different set of colors than another. I had thought that srgb was srgb the world over. But, on thinking about it, how could that be with so many different phosphors and excitation intensities.

So, I will more likely see more subtle shading on my CRT monitor, than will people with LCD monitors? Funny! I just bought a LCD projection TV as I thought the pictures were clearer than those on a CRT TV. Not arguing, just amused.

Also, I was surprised to find out that I could with the wrong Gamma setting, view all the different levels on the gamma band at the bottom of my screen, and yet have my monitor display brightly parts of images which were totally dark with a proper setting of Gamma. So, it is not just the brightness control, it is also the Gamma control. Now, I not only vary the brightness before submitting a picture, I also vary the Gamma. Varying the latter is usually scary as it really affects the appearance of a picture. I then realize that my pictures are going to look pretty bleached out to some people and pretty over contrasted to others.

Shutterfly says that they will reproduce in print the colors on your monitor if you submit srgb images and select the option saying for them not to enhance your photo. I have not tried this with some of my more color sensitive pictures, but there certainly is not any guarantee at all as to how these would look on other monitors that do not have the same calibration as mine.

How would you all like to come over and use my monitor to vote?

David.C

02/01/2005 01:53:39 AM · #6

Keep in mind, this is as I understand it and is subject to correction by those more knowledgable than I. :D

CRT monitors refresh as you described, but LCD monitors do not refresh -- that is, power is turned on and left on to each pixel as long as it is needed. It is probably true that CRT monitors have a larger gamut; they are analog devices and any color within their range is available in a smooth gradient. LCDs however, are digital devices (even if they have an analog input). As such, it does not have a smooth gradient of colors within its available range; but has only discreet steps along the way. Consider the difference between a solid line and a dotted one and you will have the right idea. The key point to this is that as long as the dots are close enough they line will appear solid.

Again, this is as I understand it, the phosphers of a CRT are influenced by what their neighboring phosphers (pixels) are displaying. This causes the displayed values of neighboring pixels to bleed into each other and become slightly blended, which produces a reduction in contrast. LCD monitors don't suffer this, so they are capable of displaying much greater contrast than a CRT is.

Both CRTs and LCDs are capable of being calibrated to display an image the same when viewed side by side -- within the limitations of the equipment (the LCD will appear sharper, for example). The key is to calibrate the monitors.

BTW: the gradient strip at the bottom of the voting screen is a brightness test -- it does not check the calibration of the monitors display gamma. Two monitors set at different gammas can be calibrated to show the brightness strip properly, but will still display images differently. Here is a good site, with easy to follow step to calibrate a monitor. While a hardware calibration system will produce more consistant results, the methods on this site can get very close with a minimal of effort and expense.

David