Why does 50% grey in Photoshop show up as 45% in Premier on the Lumetri Scope?

[GeorgeMonteiro]

I created a simple 10 step chip-chart in Photoshop as a demonstration to a student of how to use the Lumetri scopes in Premier and noticed that the values don't match up between Photoshop and Premier.  In fact, only the 0% and 100% values line up.

The 10% bar comes in at about 11%

The 20% at about 18%

The 30% at about 27%

The 40% at about 36% etc...

Until the 90% bar is back up to about 89%

Is there a reason for this?  Please see the attached images. 

When I use Premier Graphics program the bars come out exactly right.

[R Neil Haugen]

Photoshop is oft set for straight sRGB or farther out for color spaces, gamma/gamut. Often worked with gamma 2.2.

Premiere is straight Rec.709 video sRGB, with an assumed gamma of 2.4.

I would guess that is the issue here.

Neil

[salvo34]

That's pretty close and I doubt it will improve to be exactly the same in psd and ppro.

I did same thing years ago ( color chart ( rgbcmyk and 10 zones of greyscale ) and find it's not exact, even if you choose color space of hdtv rec 709 in psd, etc.

Best bet is to show the color 'bars' in ppro as a reference in that program.  Then it's a matter of calibration of the individual monitors how close it is to SMPTE standard.

In the old days a zone 10 thing was used for Minor White's large format b&w ( mistakenly attributed to Ansel Adams mostly ) manipulation of contracting and expanding the zones with a two bath developer. Now it's kinda a lost art and not many even know what it is for.... the zone system.

It won't translate well into video.

[R Neil Haugen]

I created a chart in Premiere using the EGP ... just made a series of rectangles, filled them with white but set brightness of each box with a mask on so that was all that was showing and watched the scopes.

 

This was in 16 equal separations for brightness for the main boxes, with a narrow one at 55 and a small box at 45. I've used this coupled with a ramp as below to test how say LUTs are modifying the image. Or what specific tools are doing when set a specific way.

 

Neil

[salvo34]

This is getting interesting. Thanks for sample, Neil.

Somehow I think the link between tones and IRE and NITS should somehow relate to lattitude. Raw is X number of stops ( theoretically very broad ), while LOG is also X number of stops ( 13 ?? - 14 ?? ). But just picking 16 out of thin air doesn't really do anything other than supply you with a tonal range that may or may not represent the capability of the media to reach those levels ( ylift, ygamma, ygain ) legally.

??

Nice to make stuff though... so you can compare or something ?

Let's say you print that scale at 300 dpi and use it when you shoot ... like everyone shoots charts at the beginning of a episode or film etc... so the post guys has a reference ... lit with the right light ( WB ).

fascinating.

[salvo34]

https://thephoto.exchange/2018/02/20/minor-whites-zone-system-manual-revisited/