CurtPalme.com Home Theater Forum

AFryia · Posted: Fri Mar 21, 2008 3:59 pm Post subject: 2.21Gamma Delta E = 2 Baby!!

Who needs Gamma Correction?

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

So you're using the HCFR sensor? Did you build your own?

GEBrown · Joined: 08 Mar 2006 Posts: 729 Location: Denver

Numbers and specs are nice, but what does it LOOK like?

Moose · Joined: 09 Mar 2006 Posts: 788 Location: Minnesota

To the ignorant amoung us - what do the graphs mean?

garyfritz · Joined: 08 Apr 2006 Posts: 12088 Location: Fort Collins, CO

BTW, AFryia, you COULD benefit from some gamma boost. Your color temps are right on, but your gamma is actually a bit off. 2.21 is the approximation that HCFR calculated, but you're not following it exactly. Look closely at your luminance chart. Below about 35 IRE you're below the 2.2 line, and above 35 IRE you're above it. Expand the Y axis on that chart and I think you'll see your low-IRE levels are very low. It's not terrible, to be sure, but you could bring out a bit more shadow detail if you boosted the low end a smidge.

ecrabb · Posted: Fri Mar 21, 2008 7:46 pm Post subject:

I'm so interested in the whole HCFR thing, but I haven't taken the time yet to wade through the mountain of info to read up on it. AFryia, would you be willing to write a simple one-paragraph write-up on the process with the G70? That would be great to just have a quick overview of what you're doing. Also, I know I won't ever have time to build a DIY sensor, so I'd probably go the Spyder route. So, are you using an HTPC or processor to get response that flat, or...?

Thanks,
SC

AFryia · Posted: Fri Mar 21, 2008 9:40 pm Post subject:

ecrabb · Posted: Fri Mar 21, 2008 9:46 pm Post subject:

KrisRoberts · Joined: 21 Jan 2007 Posts: 115 Location: San Diego

How did you position the probe?

I played with HCFR last year with both a Spyder2 and an EyeOne.

I used a tripod to hold the probe in the center of the screen, but was only able to get good results with the probe facing the projector. Several people suggested that it was better to point it at the screen, but I was never able to get that to work well. I tried making a little black tube from a painted paper towel roll to have it look through and not see its shadow, but neither probe would respond well looking at the screen.

With the probe pointing at the projector, I found the Spyder2 to be a little slow but it was consistent. The EyeOne responded quickly, but I was frustrated because it would give me one set of values one day and the next time I used it the numbers would be different without any changes to the projector.

I'm itching to take another pass at it, and would be interested in hearing how you had yours setup.

AFryia · Posted: Fri Mar 21, 2008 11:53 pm Post subject:

My probe sat on a tripod in the middle of the screen facing the PJ sitting ~6" off the screen.

I can read off the screen down to about 20-25 IRE. I needed to see what was going on lower than that so I face the probe toward the PJ and live with whatever the matte white screen will do to the color.

On trick I did was stretch and hold a piece of light string from my green lens to the probe to adjust the angle of the probe.

I believe the Eye-One needs an occasion recalibration of the black reference. Not sure though never used one.

Nashou66 · Joined: 12 Jan 2007 Posts: 16171 Location: West Seneca NY

I Agree that it would be nice for some one who has experiance using a colorometer with HFCR to make a step by step instuction set for general use.it doesnt have to be projector specific either. I have a eye 1 sensor and down loaded HCFR and am lost. I thought i was using it rigth but my readings were all over and i know it wasnt that bad. I know i was doing something wrong so i just gave up for now.

Athanasios

Mark_A_W · Posted: Sat Mar 22, 2008 1:22 am Post subject:

I've been unable to get really sensible results for Gamma with my HCFR setup.

My gamma curves, both for the XG and the 24" Sony CRT monitor are all over the shop (XG is worse though).

Am I the only one struggling with Gamma and HCFR?

AFryia (what's your name anyway? You never sign off with it..) I see you're pointing the sensor at the PJ, from your description?

SC, it's REALLY, REALLY simple. It will take you 10 minutes to get up and going once you have a sensor.

- Install hardware (usb driver for the sensor) and software (version 2). Play on a Monitor (CRT preferred) first.
- Run it, create a new file, use the internal images (called "View Images" = THIS IS IMPORTANT TO KEEP IT SIMPLE), use the XG LC/G70 cal file I uploaded here.
- Do RGB measurements by pressing "Mesure Gray Scale" (They can't spell...Measure or Grey...I forgive them, it's the only flaw Smile

)
- Fiddle with Bias and Gain on G70.
- Bask in your Calibration expertise.
- Get a Tripod and stick the sensor 300mm or so away from the screen, point at the screen and up a bit.
- Rinse and repeat for the G70.
- It's almost too easy.

Just get a sensor and a tripod, and do it.

MikeEby · Joined: 24 Jun 2007 Posts: 5237 Location: Osceola, Indiana

AFryia · Posted: Sun Mar 23, 2008 5:56 pm Post subject:

**kal** · Posted: Mon Mar 31, 2008 2:55 pm Post subject:

FWIW, I've been able to get my Spyder2 to work just fine down to 10IRE producing very consistent results I set the read time to 1000ms. I use the default 300ms when taking readings from 20-100 but then increase to 1000ms when taking final readings just to see where the 10IRE ended up. It might even be able to do 5IRE (haven't tried) if I increase it to 2000 or 3000.

Some questions:

So what is the target gamma on CRT projectors? I hear 2.2, but also read that 2.5 is the right thing when I start searching around in really old AVS forum archives. What is the right target?

What is delta E anyway? in this screenshot below, a Delta E value is taken at each of the 10 IRE steps... what does it represent?

Brian Hampton · Joined: 22 Apr 2006 Posts: 1173

HI,

Nice work...

Some questions...

1) Do you have AKB dis-abled on the G70?

2) Since you're using the HFCR sensor... I assume you're using HFCR however,.. While it looks like it ... it's somewhat different. So,... Is that HFCR?

3) If it is HFCR... How did you ask it to start at 7.5IRE instead of 0 and how did you measure that data point. (Did you just alter the measured values after the measurements were taken?)

Thanks,... I love HFCR and even the 709 disc. I'm using a Spyder II that I got for about $80 new at some point. I compared it's readings to an EyeOne (?) sensor belonging to someone on AVS and they responded identically which is one reason I'm not itching to replace it as my color meter.

-Brian

Brian Hampton · Joined: 22 Apr 2006 Posts: 1173

Quote "Who needs Gamma Correction?"

Bruce Banner?

MikeEby · Joined: 24 Jun 2007 Posts: 5237 Location: Osceola, Indiana

AFryia · Posted: Tue Apr 01, 2008 1:07 am Post subject:

AFryia · Posted: Tue Apr 01, 2008 1:17 am Post subject: