I’ve been really satisfied with the Samsung PS63C7705. Owned it now for over 2 weeks and I was really impressed by the picture quality. And as many of you know I measured the black level low (at 0.02 to 0.03 cdm2) and some other reviewers measured it higher. Some of the explanation is probably my equipment being a little unprecise (the only two low level “luminance” meters I have are a Spyder and a i1 D2).

Black level on the Samsung C7705 plasma.But yesterday I was watching some tv shows and I discovered the black level was brighter than normal with a blue LCD like tone. At first I thought it was the recording/encoding (some questionable mkv’s), so I didn’t really think more about until today where I still couldn’t believe how bad it was (I could easily see it with the lights on in the room). I was certain that the black level was a lot better when I calibrated it and I remembered the black at 0IRE having a red tone, not a blue tone. So something was wrong.

I updated the Samsung to firmware 1016 just before posting my updated settings a few days ago (it was firmware 1013 before), so I thought that might have been the reason.

My setup consists of an Onkyo TX-NR808 receiver, a Mac Mini running Plex/eyeTV and a Samsung 6900 3D bluray player (and some other non relevant-equipment). Everything is run through my receiver so I thought that might be the problem also (it just had a firmware update too). But then I started my PS3 and wanted to do some testing. I instantly noticed that the PS3 seemed to have a darker black.

When I loaded up the calibration disk (I just took the first one I had around which was an old ColourHCFR DVD) I could see the screen changing the black level to something a lot brighter. Strange. I then entered the TV menu, but no matter what I tried to adjust I couldn’t get the black level lower). So what was the difference between the two signals (PS3 displaying it’s menu and PS3 showing a DVD)? The resolution is the same – upconverted to 1080p. But then I noticed the difference. The PS3 menu is shown at 60Hz – The DVD is shown at 50Hz.

Now I spent one hour testing this with all kinds of calibration disks and settings. Using both my Mac Mini, Samsung BD player and the PS3 – both connected directly to the screen and run through the Onkyo. When the signal is 50Hz the black level is bad/bright. When it’s 60Hz it’s good/dark. There is no way for the 50Hz black to be adjusted on the TV down to the level of the 60Hz black. The white level doesn’t change and the black level at 60Hz stays solid so it’s not some power save feature that turns on when the screen is dark at 60Hz.

Conclusion:

  • 50Hz makes the screen have a black level with a blue tone with a luminance level of about 0.06cd/m2 (LCD like).
  • 60Hz makes the screen have a black level with a red tone with a luminance level of about 0.02-0.03cd/m2 (noticeably darker)

Now – I need others to test this just to make sure it’s not just my screen that exhibits this. :-)
Try loading up my settings posted here (as these should make the black level as dark as possible).

If you have a HTPC or Mac connected it’s quite easy to switch between 50Hz and 60Hz and watch the black level (just turn the desktop colour to black). And please do this in a completely dark room.

If you have a PS3 (or BD player capable of outputting at the right Hz like the Samsung) try loading the ColourHCFR calibration DVD (it’s mastered in 50Hz) and check the 0/10IRE pattern. Afterwards try loading the AVCHD calibration disk (which is 60Hz) and check the 0/10IRE pattern. I was able to replicate this no matter the video settings of the PS3 (black level, RGB, YCbCr etc.).
The Samsung BD player is a little funny. If you play a disc at 60Hz and eject the disk the menu is still 60Hz. If you play a 50Hz disk it changes the menu system to 50Hz. So you can even see the menu looks a lot better at 60Hz.

And btw – 24Hz is the same black level as 60Hz – only 50Hz being the problem with brighter black levels. When watching TV with the build-in tuner the black level is also “brighter” (as it’s 50Hz PAL in Denmark).

So why does the black level change? The answer is probably best explained in a post about the same problem on Panasonic plasmas on avforums.co.uk – although it might also be a firmware problem.

I just didn’t expect it to make such a visible difference :-/

Update 2010-08-14:

Ok. I’ve just had it confirmed on a danish forum that people are experiencing the same thing.

When the TV is fed with a 25Hz or 50Hz signal the black level is bright.
If the signal is 24Hz, 30Hz or 60Hz the black level remains where they should.

Also – when viewing a 24Hz signal (eg. BD) and you engage Cinema Smooth mode you get the brighter black level also (this should be easy for everybody to test – but make sure you do it in a completely dark room).

The theory is that 24Hz, 30Hz and 60Hz is displayed at 60Hz and 25Hz, 50Hz is displayed at 100Hz (which results in the brighter black level). 24Hz with Cinema Smooth is displayed at 96Hz (with the brighter black level).

One of the users on the danish forum found out that this is actually an “old” problem with many Samsung plasma’s.

PS58B850/ Cinema smooth Black level problem – CNET Samsung Forums
Samsung cinema smooth issue – AVS Forum

You can see the difference here:

Update 2010-08-17:

Just wanted to add that the user fredtoft (at recordere.dk) measured the PS63C7705′s black levels with a Klein K10 (capable of measuring down to 0.0002 cd/m2 and the same meter used by hdtvtest.co.uk and avforums.co.uk in some of their reviews). He is an ISF and a THX certified calibrator so I guess his measurements are to be taken seriously. :-)
You can see the posts here (in danish), but to sum it up:

With 60Hz or 24Hz input (Cinema Smooth off): 0.003 cd/m2 0.0009 fL
With 50Hz or 24Hz input (Cinema Smooth on): 0.034 cd/m2 0.0099 fL

These readings are a lot more precise than what I can do with the colourimeters I have (and also a lot lower).
The C7705 is measuring lower than the Panasonic VT20/VT25 and almost at Kuro levels. Some speculation suggests that the black levels are better on the 63″ than on the 50″, but we’ll see once flatpanelshd.com has tested their PS50C7705.

It has also been confirmed that the difference in black levels existed in firmwares before 1016 (which i’m currently running). So avoid running 50Hz or using Cinema Smooth if you want good black levels. However – 0.034 cd/m2 is still better than most LCD’s and plasma’s currently available.