When calibrating a monitor, should I create different profiles with different light situations?

Question

When calibrating my monitor (Eizo Flexscan EV2736), should I create different profiles for different light situations? For example a profile when the rooms light is switched on and a profile when the light is off? Or should I do calibration without the light on in the room and do an adjustment of the screen brightness or adjustment with colorimeter when the light is on?

I did calibration now using the Eizo EX2 colorimeter and the Easypix Software. When light is on, the resulting calibration gives very warm colors on the screen. It is totally different to the sRGB mode of the montior. I don't think, this is a correct calibration...

Answer 1

Do you mean that the calibrated result is different depending on whether you calibrate with the ambient light on and off? That is, if you create two profiles in these two conditions and then compare them (either by observing the correction curves in the software or by switching between them quickly while looking at a test photo), they happen to be different?

If so, this is a measurement problem: probably the ambient light leaks into the sensor. The sensor should be placed right against the screen surface without gaps (but without pressing it so as not to distort the image/colours). The sensor should measure the light from the monitor, and it doesn't depend on the ambient light.

If you can't eliminate the gaps, you should do the calibration in darkness. If you say that your result is very different to the built-in sRGB, you should try it just to see if it has an effect. (Eizo's factory settings can be trusted, in general).

If, on the other hand, you are saying that the same calibration looks different with different lighting, this is perception problem. Objectively, the image on the screen is the same.

(Some monitors have an ambient light sensor and a function to self-adjust, but usually they are supposed to adjust only the brightness/contrast, without affecting colours. But in a professional environment, this feature is not used, and generally shouldn't be relied upon).

You should certainly not try to tweak the profile "to taste". What's the point of calibration then? Instead, you should adjust the environment. This doesn't only concern the ambient environment. Strive to use neutral grey colours for the windows and other GUI elements; this way your eyes will adjust better to the on-screen environment (which we know is stable after calibration). Trust more what you see on the screen than what you see around you. (Once you confirm the calibration works properly, of course).

Answer 2

You should create a single color profile for backlit or light-emitting monitors because ambient lighting typically does not change the colors that are displayed, but mainly alters your perception of those colors.

The most effective way to ensure consistent results when you edit to to create a consistent editing environment, whether that is with the lights on or off. If you cannot control the ambient lighting, you can do rough edits early, then fine tune later when you are able to control the lighting. Even if you are able to control the ambient lighting, you may find it helpful to leave fine tuning for the end of editing sessions because perception can drift.

Answer 3

The target temperature (and to a lesser extent tint - lesser because your lighting environment should match very closely to somewhere along the color temperature axis of black body radiators) of the calibration should match your ambient lighting. The best results will be obtained when the ambient environment matches an industry wide standard: e.g. D55 or D65, etc.

If you can't insure a controlled lighting environment when editing, then you've got no way of knowing if the adjustments you make to your images based on what your eyes are seeing are to correct for color casts in the image itself or to correct for your misperception of colors because you have a mismatch between your monitors target "white" and what your eyes are perceiving as "white" based on the ambient lighting.

In such a case, if your goal is to produce accurate colors, your best option is to use numerical measuring methods to set the white balance of an image. Hover the mouse over a piece of the image that is neutral gray (such as a calibrated test target) and adjust the color temperature and white balance correction until the RGB values are all the same.¹ For even better results, use a color calibration tool such as the X-Rite Color Checker to create a profile that matches numerous colors.

_{¹ i.e. (185,185,185) or (236,236,236)}

Answer 4

Yes. Quoting Dr. Poynton: for optimum colour appearance, in a dark ambient you may increase the gamma to 2.4 or 2.6, and in a bright ambient you may decrease the gamma to 2.2 or 2.0. The monitor transfer function cannot be specified without including the ambient lighting level, that's Colour Appearance Modelling 101. (Canadian-English spelling.) Your eyes vary much more than your monitor.

Ideally you'll grade your images with the same monitor settings and in the same ambient as the intended delivery. In practice only Digital Cinema does this.