Dell S718QL 4K UHD Laser Projector Review – Calibration Settings

Dell S718QL 4K UHD Home Theater Projector Review – Calibration Settings: Calibration Presets Notes, Best Mode Calibration, Brightest Mode Calibration & 4K Calibration

My calibration report for Dell’s S718QL is going to be a bit shorter than usual. Simply put there are very few picture controls to begin with and they are global further diminishing their usefulness. During my time with the projector I spoke with a Dell engineer who answered all my questions listened to my feedback in regards to my experience with the S718QL. He could not promise me anything but seemed to indicate that it might be possible to rectify some of my concerns in future updates, here’s hoping.  [Editor’s note: While it’s possible Dell would update the firmware of this projector, I would consider it highly unlikely they would add what Eric says is needed. Therefore,when it comes to the picture, what I describe elsewhere in this review, is what you should expect in terms of performance. Adding a CMS or separating the settings by mode would be massive rework of the firmware by Dell.  At best, perhaps the next generation… -art]

The Dell S718QL has 4 video presets (Bright, Presentation, Movie, sRGB & Custom). There are 3 lamp modes and one of them is hidden. Let me explain. In the menus you will find 2 lamp modes (normal & ECO). However, if you choose Bright as your picture mode it runs the lamp even brighter regardless if you have the lamp set to normal or ECO. The fan speed (and noise) will increase to deal the increased heat output.

For my best/dark room 1080p calibration, I used sRGB mode (normal lamp). I used sRGB mode rather than Movie because it’s color gamut was slightly better. Like so many other projectors I have calibrated the S718QL clips the whites ever so slightly (230 or so) and lowering contrast does nothing to help this matter. There is only one set of white balance (gain) adjustments and no gamma controls. So, although I would have preferred a gamma of 2.4, I set my target to 2.2 based on the projectors performance and was able to get an average of 2.14. The S718QL before white balance/gamma DeltaE ranged from 3.5 on the low end to 11 on the high end. After calibration I was able to get it to 2 or less across the board (10-100IRE). DeltaE of 3 or below is considered excellent. White balance averaged around 6400K.

I wanted to set contrast 2 clicks lower from its default of 50 because it helped my gamma and white balance a small amount at the 90 and 100IRE range. I did not however because by making any changes to contrast, brightness, color or tint would toss me out of sRGB mode and into custom mode. Now other projectors have done this before by coping your settings from your chosen mode, in this case sRGB and applying them to custom mode. Problem here is that is does not do this, it just places you in custom with its far from desirable picture performance. So, in order to stay in sRGB mode I can’t touch any picture controls except for white balance.

The S718QL has no CMS controls. You have to live with what it gives you, which is why I choose sRGB because it displays the best color gamut of all the picture modes. Now if you look at my color gamut charts (below) you will see there are slight differences between before and after. You may ask with no CMS controls why aren’t they the same? Well the white balance gain calibration I did has an effect on color gamut. Over all the gamut is not terrible but it’s far from great too. Blue and yellow fair the best. Magenta is over saturated at 100%. Red is under saturated across it’s range. Green is under saturated across its range except for 100% which is over saturated. Oddly the hue of cyan got worse after calibration with it now running towards green.

Delta E is a metric for understanding how the human eye perceives color difference. The term delta comes from mathematics, meaning change in a variable or function. The suffix E references the German word Empfindung, which broadly means sensation. Simply put, look at Delta E as a measure of grayscale/color accuracy. 3 and under is considered ‘Excellent’ and imperceptible by the human eye.

For my bright room 1080p calibration, I choose bright mode with it’s hidden ‘brightest’ lamp output. Because the white balance calibration I performed on sRGB mode is global I can’t do it here, otherwise it ruins my dark room/best calibration. White balance in bright mode was a bit off putting with its excessive green tint, but I found a way to improve it a little bit. There is a “feature” found in many business/education projectors called wall color that is now making its way over to some ‘crossover’ projectors like the S718QL.  I usually ignore these kinds of setting because all they do is further deviate from the SMPTE standards I try so hard to adhere to. Anyway, in this case setting wall color to dark green helped reduce the green push a little bit. You will need to set wall color back to white when using my best/dark room calibration because this setting is global.

Before & after DeltaE is off the chart at 12+ across most of the spectrum. Gamma averages 2.14 but is far from linear with it getting too dark at 50-60IRE and a big spike of over brightness at 90IRE. Color gamut has many, many problems, just take a look at my charts (below).

Lastly, I attempted a 4k/HDR calibration. For starters, no matter what mode you are in when you send the S718QL an HDR signal it automatically switches into a HDR mode. Well it’s not a labeled mode like sRGB or Cinema. What it does is gray-out (disable) all picture setting except for white balance and HDR mode. There are 2 HDR modes, auto and bright. Auto measured very flat (see EOTF/gamma chart). Bright measured a bit brighter from 0 to 55 IRE.

Like with my bright room calibration I did not want to touch the white balance controls and ruin my best/dark room 1080p calibration. This left me my one little cheat. The white balance in HDR mode is extremely blue so I set wall color to light blue. This reduced blue a tiny bit but like my bright room calibration DeltaE was very high, +12 from 50 to 100IRE. Dell does not advertise the S718QL as covering the P3 color gamut for 4K/HDR but when speaking with Dell’s technician he said it should cover 130% of REC.709.

So, I used the P3 color gamut chart to measure the projectors capabilities. Well the results are not very good, it’s not the fact the colors don’t make it out to the P3 targets that bothers me, it’s the hue of some of the colors are off by quite a bit. It appears the color gamut is heavily tied to the white balance, which in this case is very blue. Look closely at the white dot in the CIE charts. This dot represents the white balance which is in the blue area far from its D65 target. Now all of the 6 colors seem to emanate from that point, driving some of them far off course. Although magenta seems to have the largest error, yellow is the most troubling with it being pulled so close to green.