Samsung C34J791/CJ791 Monitor Review

Tested using Methodology v1.0
Updated Jan 22, 2019 at 09:32 am
Samsung C34J791/CJ791 Picture
Mixed Usage
Media Creation
HDR Gaming
Size 34"
Resolution 3440x1440
Refresh Rate 100 Hz
LCD Type
Variable Refresh Rate

The Samsung C34J791 is a 34'' ultrawide monitor with mediocre picture quality. It has a high contrast ratio due to its VA panel and displays deep but not too uniform blacks. It is more suitable for an average lit room as it cannot get very bright to fight bright room glare. It has great gray uniformity, which is great for browsing the web, but the bad viewing angles make it unsuitable for working side by side with a colleague. It has great motion handling with a fast 100Hz refresh rate, supports FreeSync and has a low input lag to please gamers.

This is a newer version of the Samsung CF791.

Our Verdict

7.2 Mixed Usage

The Samsung C34J791 is a decent monitor for mixed usage. It has a large ultrawide screen with ample resolution that favors multitasking but unfortunately, it has poor viewing angles. It is very responsive to your actions but you should avoid placing it in a very bright room as it cannot fight bright room glare.

  • Excellent low input lag
  • Excellent resolution and size
  • Image degrades when viewed at an angle
  • Lack of HDR support
7.1 Office

This is a monitor with decent performance for office use. Its large screen size and great resolution will allow you to do more at the same time, but unfortunately, the poor viewing angles and bad ergonomics will not make it easy to share your work with your coworkers.

8.0 Gaming

The CJ791 is a very good gaming monitor. Its low input lag and excellent resolution and size offer an immersive gaming experience. It supports FreeSync so you can strain your graphics card without worrying about tearing. The fast response time ensures a crisp image with little motion blur in fast action games.

7.0 Multimedia

This is a decent monitor for multimedia. The large screen size and excellent resolution enable the monitor to display much of the multimedia content at its native resolution. However, the best picture quality is reserved for those seating directly in front since the viewing angles are bad.

7.0 Media Creation

The Samsung C34J791 is a decent monitor for media creation. The large size and excellent resolution are ideal if you open many windows at the same time, but the bad viewing angles and poor ergonomics will trouble you especially if you wish to work side by side with a colleague. However, if you work alone you will appreciate the monitor's responsiveness due to the low input lag and the crisp image thanks to the fast response time.

5.6 HDR Gaming

Unfortunately, the Samsung CJ791 does not support HDR like the Samsung CHG70.

  • 7.2 Mixed Usage
  • 7.1 Office
  • 8.0 Gaming
  • 7.0 Multimedia
  • 7.0 Media Creation
  • 5.6 HDR Gaming
  1. Updated Aug 16, 2019: We remeasured the 60Hz input lag, as the previous measurement is impossible. We've updated the input lag measurements and the score.

Test Results

Curved Yes
Curve radius 1500R
Weight (without stand)
15.0 lbs (6.8 kg)
Weight (with stand)
16.5 lbs (7.5 kg)

The design of the Samsung CJ791 is very good. It is identical to the design of the Samsung CF791. It has the same flat round stand that supports the monitor well and prevents serious wobbling. You can adjust the height and tilt, but you cannot swivel or rotate the screen and this will disappoint those who regularly share their work with a colleague. Due to the curve profile, it looks slightly thick, and finally, the overall build quality is very good and you should have no issues with it.

9.6" (24.4 cm)
12.2" (31.0 cm)

The stand of the Samsung C34J791 is round and flat. It supports the monitor well and only allows minimal wobbling.

Height Adjustment
3.9" (9.9 cm)
Switch portrait/landscape No
Swivel Range N/A
Tilt Range -20° to 15°

The tilt range varies along the height adjustment positions:
@ top: 15° to -20°
@ bottom: 2.5° to -17.5°

The ergonomics of the monitor are poor. You will not have an easy task adjusting it to a comfortable position. You can adjust the height and tilt the screen, but you cannot swivel or rotate it to portrait.

Wall Mount VESA 100x100, VESA 200x200

The back of the monitor is plain and it looks identical to the back of CF791. It has a compartment (that comes with a cover) that houses most of the inputs. Outside this compartment, there are two USB ports and a headphones jack that are pointing outward.

Just like the CF791, the CJ791can be VESA mounted in either 100x100 or 200x200 VESA wall mounts using the included adapter.

The monitor offers cable management through the stand.

0.4" (1.0 cm)

The borders are thin and look elegant. They are metal and have a chrome finish just like the CF791. In the image, they look more white due to the camera flash.

Thickness (with stand)
8.3" (21.1 cm)
Thickness (without stand)
6.5" (16.5 cm)

The monitor is thick, especially when placed on its stand. If you VESA mount it, it will not protrude much but it will not look very thin either due to the curve.

Build Quality

The Samsung C34J791 has a very good built quality. You will not find any gaps or loose ends and you should not have any issues with it.

Picture Quality
Picture Quality
Native Contrast
2904 : 1
Contrast with local dimming

Just like the CF791 the Samsung C34J791 has a very good native contrast ratio due to its VA panel. Blacks look deep in a dark room and this improves picture quality.

Picture Quality
Local Dimming
Local Dimming

The Samsung CJ791 does not have a local dimming feature. The video is for reference only.

Picture Quality
SDR Peak Brightness
SDR Real Scene
251 cd/m²
SDR Peak 2% Window
248 cd/m²
SDR Peak 10% Window
249 cd/m²
SDR Peak 25% Window
249 cd/m²
SDR Peak 50% Window
248 cd/m²
SDR Peak 100% Window
248 cd/m²
SDR Sustained 2% Window
248 cd/m²
SDR Sustained 10% Window
249 cd/m²
SDR Sustained 25% Window
249 cd/m²
SDR Sustained 50% Window
248 cd/m²
SDR Sustained 100% Window
248 cd/m²

The CJ791 has decent SDR peak brightness. It is ok for an average lit room but it cannot overcome the glare of a bright room. The level of brightness remains constant across the various bright window sizes and this is great. The SDR Real Scene measurement appears a little higher due to uniformity issues at the position of the screen where the measurement is made.

The tests were done using the 'Custom' (calibrated) Picture Mode.

Picture Quality
HDR Peak Brightness
HDR Real Scene
HDR Peak 2% Window
HDR Peak 10% Window
HDR Peak 25% Window
HDR Peak 50% Window
HDR Peak 100% Window
HDR Sustained 2% Window
HDR Sustained 10% Window
HDR Sustained 25% Window
HDR Sustained 50% Window
HDR Sustained 100% Window

HDR is not supported.

Picture Quality
Horizontal Viewing Angle
Color Shift from Left
31 °
Color Shift from Right
30 °
Brightness from Left
44 °
Brightness from Right
40 °
Black Level from Left
13 °
Black Level from Right
13 °
Curve Radius 1500 R

Poor horizontal viewing angles as expected for a VA panel monitor. As soon as you deviate from the center axis, the image darkens and is no longer accurate. This is not good if you need to share your screen with a colleague.

Picture Quality
Vertical Viewing Angle
Color Shift from Below
26 °
Color Shift from Above
23 °
Brightness from Below
37 °
Brightness from Above
35 °
Black Level from Below
6 °
Black Level from Above
5 °

The vertical viewing angles are poor. Anyone standing next to you will see a much darker image than what you are seeing. In order for them to see the same image quality, they have to bring their head to where yours is.

Picture Quality
Gray Uniformity
50% Std. Dev.
4.951 %
50% DSE
0.112 %
5% Std. Dev.
0.915 %
5% DSE
0.059 %

The gray uniformity of the CJ791 is great. In the 50% gray image, you can spot some clouding and the sides look darker. However, there is almost no dirty screen effect (DSE) and this great news if you spend a lot of time surfing the web.

In the 5% gray image the uniformity is better and no DSE is noticeable.

Picture Quality
Black Uniformity
Native Std. Dev.
2.766 %
Std. Dev. w/ L.D.

Poor black uniformity for the Samsung CJ791. Just like the Samsung CF791 there is scattered clouding in various areas of the screen that most people will notice when viewing dark scenes in a dark room.

Picture Quality
Pre Calibration
Picture Mode
117 cd/m²
Luminance Settings
Contrast Setting
RGB controls
Cool 1
Color Temperature
6879 K
White Balance dE
Color dE

The out-of-the-box color accuracy of the Samsung C34J791 is decent. The Picture mode with the best results is 'Custom'. Both the white balance dE and the color dE are higher than 3, so most enthusiasts will notice some gray and color inaccuracies. The image has a slight red-yellowish tint due to the slightly warmer color temperature and gamma does not follow closely the target curve resulting in images that are sometimes brighter and sometimes darker than they should be.

Picture Quality
Post Calibration
Picture Mode
100 cd/m²
Luminance Settings
Contrast Setting
RGB Controls
Color Temperature
6466 K
White Balance dE
Color dE

After calibration, the color accuracy is excellent. It is impossible to spot color or gray inaccuracies without the use of a colorimeter as both white balance dE and color dE are well below 1. There is no more red-yellowish tint as the color temperature is corrected closer to the 6500K target and the gamma follows the target curve very closely.

You can download our ICC profile calibration here. This is provided for reference only and should not be used, as the calibration values vary per individual unit even for the same model due to manufacturing tolerances.

Picture Quality
SDR Color Gamut
sRGB xy
95.4 %
Adobe RGB xy
81.8 %

s.RGB Picture Mode: Custom (calibrated)
Adobe RGB Picture Mode: Custom

The Samsung C34J791 has excellent coverage of the s.RGB colorspace. However, the coverage of the wider Adobe RGB colorspace might not be enough for professionals in the media and publishing industry.

Picture Quality
SDR Color Volume
sRGB in ICtCp
99.2 %
Adobe RGB in ICtCp
89.5 %

s.RGB Picture Mode: Custom
Adobe RGB Picture Mode: Custom

Excellent coverage of the SDR color volume. The monitor is capable of displaying a wide range of colors in various luminosity levels.

Picture Quality
HDR Color Gamut
Wide Color Gamut
DCI P3 xy
Rec. 2020 xy

HDR is not supported.

Picture Quality
HDR Color Volume
DCI-P3 in ICtCp
Rec. 2020 in ICtCp

HDR is not supported.

Picture Quality
Image Retention
IR after 0 min recovery
0.14 %
IR after 2 min recovery
0.00 %
IR after 4 min recovery
0.00 %
IR after 6 min recovery
0.00 %
IR after 8 min recovery
0.00 %
IR after 10 min recovery
0.00 %

The overall performance of the monitor in image retention is good. There are some faint signs of image retention immediately after our long exposure test that go away quickly and won't be noticeable in normal content.

Picture Quality
Color Depth
8 Bit

The Samsung C34J791 has an excellent gradient performance. You can hardly notice any banding, as the transition from light to darker shades happens smoothly in almost all colors. This is an improvement compared to the CF791.

Picture Quality
Color Bleed
Pixel row error
0.001 %
Pixel column error
0.001 %

The Samsung C34J791 produces a very small amount of color bleed when it displays large vertical bands of uniform colors. However, it is unlikely that you will notice this during normal usage.

Picture Quality

The Samsung CJ791 has good reflection handling. The matte finish diffuses reflections across the screen making them less annoying. However, this does not work very well in a bright room where reflections can become distracting.

Motion Blur
80% Response Time
4.9 ms
100% Response Time
14.0 ms
Best Overdrive Setting

Response Time Standard
Response Time Faster
Response Time Fastest

The Response Time 'Fastest' is the recommended setting as it gives the best results. However, in cases where there is a darker background in the image, some blue trail can be seen. If you notice this then switch to the 'Response Time Faster' setting, and this should eliminate the issue.

Image Flicker
Flicker-free No
PWM Dimming Frequency
>1000 Hz
Black Frame Insertion (BFI)
BFI Maximum Frequency
BFI Minimum Frequency

Update 05/16/2019: The dimming frequency field has been updated to include '>1000 Hz' for monitors with high flicker frequencies.

There is no visible backlight flicker. However, at lower brightness levels, the backlight flickers at a frequency of 1260Hz which is very high and it is unlikely that you will notice anything. In the PWM score, we note 0 Hz as the flicker frequency is higher than 1000Hz.

Unfortunately the monitor does not support a Black Frame Insertion (BFI) feature to make the image look crisper.

Refresh Rate
100 Hz
Factory Overclock
Variable Refresh Rate
G-SYNC Compatible
VRR Maximum
100 Hz
VRR Minimum
< 20 Hz
VRR Maximum With OC
VRR Supported Connectors DisplayPort, HDMI

The Samsung C34J791 has a native refresh rate of 100Hz that is better than the common 60Hz, but not as great as the 144HZ of the higher-end gaming monitors like the ASUS PG279QZ

The monitor supports FreeSync in two modes. The 'Standard Engine' with a limited range of 80 to 100Hz and the 'Ultimate Engine' with a range of 20 to 100Hz.

This monitor is the newer version of the Samsung CF791 and does not have the compatibility issues we encountered with our GTX1060 graphics card and the CF791 monitor.

Input Lag
Native Resolution
5.7 ms
Non-Native Res @ Native Refresh
5.8 ms
Native Resolution @ 60 Hz
9.1 ms
Variable Refresh Rate
6.0 ms
10 bit HDR
Black Frame Insertion (BFI)

Update 08/16/2019: We remeasured the 60Hz input lag, as the previous result was impossible. We've updated our scores.

Excellent low input lag and a great improvement over its predecessor the CF791. The input lag remains low even at non-native resolutions (we tested ours at 2560x1080@100Hz), or when the monitor is in VRR mode.

Resolution and Size
Native Resolution 3440 x 1440
Aspect Ratio 21:9
Megapixels 5.0 MP
Pixel Density 110 PPI
Screen Diagonal 34.0 inches
Screen Area 411 sq inches

The Samsung C34J791 is a large 34-inch wide aspect ratio monitor. It has a great 3440x1440 resolution that allows you to easily multitask and place several windows side by side.


For the two USB 2.0 ports on the back to work, you must have one of the two USB-C serve as a USB hub downstream. The source will also need a USB-C port for the entire setup to work.

Total Inputs
DisplayPort 1 (DP 1.2)
Mini DisplayPort No
HDMI 1 (HDMI 2.0)
DisplayPort Out No
USB 2 (USB 2.0)
USB C 2 (Thunderbolt 3, USB, PD)
Analog Audio Out 3.5mm 1
Microphone In 3.5mm No
Digital Optical Audio Out No
Analog Audio Out RCA No
Power Supply External Brick

Compared to its predecessor, this monitor supports Thunderbolt through its USB-C connections. Both of them can be used to display video but only the one with the 85W sign can be used to charge a laptop. If the laptop supports Thunderbolt 3 then you can use its USB-C port to send video to the monitor.

Additional Features
HDR10 No
Multiple input display

The monitor has two internal speakers and supports several additional features some of which are:

  • PBP (Picture Besides Picture): In this mode the monitor can display side by side two images from different sources.
  • PIP (Picture in Picture): In this mode the monitor can overlay on the original picture a picture from a secondary source.
  • Samsung MagicUpscale: Is the monitor's function to enhance the details and vividness of lower resolution content.
  • Eco Saving Plus: Is the monitor's function to save power.
  • Game Mode: This setting changes the picture settings like gamma, sharpeness etc., making them more suitable for gaming.

On-Screen Display (OSD)

The controls are the same as the CF791.

In The Box

  • Manual
  • Power brick and Power cable
  • HDMI cable
  • Thunderbolt cable (USB-C)
  • Plastic covers for cable management
  • VESA mount adapter

Differences Between Sizes And Variants

The Samsung CJ791 we bought is the 34" model (Samsung LC34J791WTNXZA).

If someone comes across a different type of panel or if their CJ791 doesn't correspond to our review, let us know and we will update the review. Note that some tests such as the gray uniformity may vary between individual units.

Model Size Native Resolution Refresh rate Notes Year
CJ791 34" 3440x1440p 100Hz

FreeSync and Thunderbolt 3 support

CF791 34'' 3440x1440p 100Hz FreeSync support 2016

Note: The CJ791 we purchased was manufactured in August 2018

Compared To Other Monitors

Comparison picture

Left: Samsung CF791. Middle: Samsung CJ791. Right: Asus PG348Q
Unlike our other photographs, this picture wasn't taken under a controlled environment, so do not draw conclusions from it.

The Samsung C34J791 is a large screen ultrawide monitor that is great for gaming. See our recommendations for the best ultrawide monitors, the best gaming monitors, and the best FreeSync monitors.

Samsung C34F791/CF791

The Samsung CJ791 is better than the Samsung CF791. The two monitors have very similar picture quality. The Samsung CJ791, however, has a much lower input lag that makes it more responsive to your actions, and this is great regardless if you're a gamer or not. It also has Thunderbolt 3 support.

LG 32UD99-W

The LG 32UD99 is significantly better than the Samsung CJ791 for most people in the majority of uses. The LG has better viewing angles, due to the IPS panel, better ergonomics, can get brighter, supports HDR and has a 4k resolution. The Samsung CJ791 has a VA panel and slightly better blacks. It also has a faster refresh rate, a lower input lag, and curve profile for those who like it.


The ASUS ROG PG348Q is better than the Samsung CJ791 if you care about good viewing angles. The ASUS ROG PG348Q has an IPS panel whereas the Samsung has a VA one. The ASUS also has a faster response time with a smaller blur trail and better ergonomics to position it comfortably. The Samsung CJ791, on the other hand, has a lower input lag which makes it very responsive to your actions.

Acer Predator Z35P Bmiphz

The Acer Z35P Bmiphz is better than the Samsung C34J791/CJ791. The Z35P has better ergonomics than the Samsung and allows you to place in a comfortable position with ease. Also, the image remains accurate at slightly wider horizontal and vertical viewing angles on the Acer, although they are still disappointing.