Scaling 4k Resolution Monitor down by a non-whole multiple for my Mac?

[rocketfrog03]

Hi, long-time browser, first-time posting.

I know there has been previous threads discussing this, but I'm still a little confused and was hoping someone could clarify the issue.

Related threads:
http://forums.anandtech.com/showthread.php?t=2275225
http://forums.anandtech.com/showthread.php?t=2379395&page=1

I want to know if I can buy a 4k monitor (3840x2160) and scale it down to a resolution that is not a whole number multiple for my rMBP. I.e., can I scale the 4k down to 2560x1440, which is just 3840x2160 divided by 1.5.

I know that scaling 4k down to a resolution that is a whole number multiple is possible (e.g., scaling 3840x2160 to 1920x1080), which is what Apple does to make their screens "retina" or "HiDPI." Apple merely scales their native 2880x1800 displays on their 15-inch rMBPs to a double pixel configuration so that the effective resolution is 1440x900, but with four physical pixels representing one on the screen.

The reason I'm asking this is because using the native 4k resolution on a 24" screen isn't practical since text and icons are too tiny to read, and scaling the resolution to an effective 1920x1080 would make things more "retina" but would decrease my screen real estate. I feel that if I could scale the 4k to an effective 2560x1440, I would have the perfect amount of real estate and the text/icons would not be too small to read.

If I'm not able to scale 4k by a multiple of 1.5 to have an effective resolution of 2560x1440, I suppose I'll have to wait until 5k (5120x2880) monitors are available for the 24" size.

(If anyone is wondering why I don't just get a larger screen than 24", it's because the monitor is for my side monitor in my multiple-monitor setup. I use a 34" 21:9 3440x1440 monitor as my primary).

Thanks for reading.


Thread moved to All Things Apple.

-Rvenger

 

[Atomic Playboy]

I'm curious why you'd buy a native 4K screen if your intention is not to run it at native resolution; you could get a 1440P display in the same size and save money and get exactly what you're looking for. But to answer your question, it's going to depend on the monitor. I'm under the impression that every monitor will offer some degree of frame scaling to lower resolutions, but the implementation is going to vary by brand, so if you have a specific brand in mind, you should look into how it handles frame scaling from lower resolutions. I'm not familiar with Macs, but I know Windows also allows you to run at native resolution but increase the DPI on icons and text; that might also help solve the issue of text/icons being too small at native resolution.

 

[rocketfrog03]

Please correct me if I'm wrong, but wouldn't buying a 4k monitor and scaling it down increase the quality of the image? I thought that was why Mac retina screens looked so crisp - because the screens are using 4 physical pixels to represent 1 on screen pixel.

So to answer your question, my intent for buying a 4k screen would be not for the additional real estate (I'm happy with the real estate 2560x1440 provides), but to increase the quality of the images by downscaling 4k to an effective 2560x1440, much like Apple does for their rMBPs.

The 4k monitor I was considering is the Dell P2415Q (http://accessories.us.dell.com/sna/productdetail.aspx?c=us&l=en&s=bsd&cs=04&sku=860-BBFF)

 

[Atomic Playboy]

No, that wouldn't improve image quality. In fact, it's more likely to degrade image quality by introducing scaling algorithms that might not always work perfectly. The best image quality is going to be from a monitor running at native resolution. A 4K monitor at 4K will look better than a 1440p monitor at 1440p; but a 1440p monitor at 1440p will look better than a 4K monitor scaling to 1440p.

 

[rocketfrog03]

Do you think this may be a Windows vs Mac issue with interpolation algorithms? Because scaling down a 4k monitor to a lower resolution with a mac does increase the quality of the image (see youtube videos below).

The youtube videos show that scaling a 4k Dell 24" monitor down by a multiple of 2 (so scaling 3840x2160 to 1920x1080 HiDPI) increased the quality of the image. Since these examples are scaling by a whole multiple (i.e., 2) instead of a non-whole number (i.e., 2560x1440 is not a whole number multiple of 3840x2160), the scaling algorithm is probably easier.

https://www.youtube.com/watch?v=ak0_8dNohLE
https://www.youtube.com/watch?v=pyqtyVx_j_o

 

[Rakehellion]

No, that wouldn't improve image quality. In fact, it's more likely to degrade image quality by introducing scaling algorithms that might not always work perfectly. The best image quality is going to be from a monitor running at native resolution. A 4K monitor at 4K will look better than a 1440p monitor at 1440p; but a 1440p monitor at 1440p will look better than a 4K monitor scaling to 1440p.

Not true. Macs with retina scaling run the display at native resolution but scale interface elements to mimic the effects of a lower resolution.

 

[Rakehellion]

Looks like this thread was asked and answered already http://forums.anandtech.com/showthread.php?t=2438014

 

[rocketfrog03]

Thanks!

I also found some more articles that answered what I wanted to do.

http://www.anandtech.com/show/7847/improving-the-state-of-4k-display-support-under-os-x

The article explains that in order for Mac to scale a 4k monitor to 2560x1440, it first has to render the display to 5120x2880 and then scale it in half to give an effective resolution of 2560x1440.

Here's another article that explains the whole retina/HiDPI scaling effect:
http://www.anandtech.com/show/6023/the-nextgen-macbook-pro-with-retina-display-review/6
http://www.anandtech.com/show/8023/apple-releases-osx-10-9-3-improved-4k-display

 

[Tyranicus]

The article explains that in order for Mac to scale a 4k monitor to 2560x1440, it first has to render the display to 5120x2880 and then scale it in half to give an effective resolution of 2560x1440.

This works very well. I have a 15" retina Macbook Pro with a 2880x1800 panel that I run at a scaled resolution of 1680x1050.

 

[rocketfrog03]

Awesome! Thanks for confirming. Waiting for the Samsung 4k 24" to get a little cheaper so I can have a nice "retina" experience.