VF0070 gamma correction - for experts...

I am using VF0070 for image analyzing - my aim is to take RGB spectrum image and transform it into reflective spectrometer graph.
I'm encountering problems regarding on how colors as seen at the computer screen are different from their REAL RGB.
I'm taking the R,G,B pixels and make a conversion to YUV for using the Y values.
I'm measuring the Dark current and subtracting it.
My reflective spectrometer algorithm is correct but still my measured graphs are not like the should appear according to the reference graphs....
my questions are:
1. What is the gamma value which is equal to 1 ? meaning NO correction... the values in VF0070 are 0 to 100.
2. What is the Non-Linearity equation of this camera?
3. How can i correct the measured color spectrum to be like the reference of the same color ?
If i knew what the camera and the driver is doing to the real color i will be able to correct the spectrum reading to be real.
If someone can help with his knowledge, I would appreciate it very much.
Thank you very much
Ofer

Ken, there's a whole part of this that isn't stated but is obvious now. You are playing back this video as a movie on the computer screen (and therefore projector), rather than as video...
So from the start it is seriously degraded by being projected that way - in resolution, gamma, and "temporality" (lack of interlace support). And yes, it would then also be affected by differences in how Macs and PCs treat their display gamma.
My comments were aimed at a situation where one can really address maximimum quality for the situation. From the above that won't be the situation here. But you can still make improvements.
You are still taking this seriously, so here's my updated advice:
Don't change anything about the production or output - keep editing to a calibrated CRT.
Do a thorough calibration of the projector as a computer monitor. The PC should have a system for this. Calibrate both color and gamma under the normal viewing conditions. The actual calibration could be on the projector and/or in the PC.
Now take bars from FCP through all your channels to where it gets played back on the PC. Use the playback software's controls to adjust the bars playback to work as close as possible to what a video display would. You won't get very close but whatever you can do will make a huge difference.
If your software doesn't have such controls, then either:
- get playback software that does, or
- (what I would do): decide the projector's role as a video display is more important than it's computer display, and adjust the projector to the bars.
If you really want to stun them, ignore all of this, get an actual CRT video projector and mount it in the room. Get a tape, disc, or true NTSC computer output device, and adjust to bars. The difference will blow you away too.

Similar Messages

Quicktime MPEG IMX 625/50 export - how to disable gamma correction?

Hello,
Since there seems to be no support for encoding an MPEG IMX stream into a Quicktime container out of the box in Premiere CS5.5 I have managed to cheat IMX in there by using Quicktime component files from a Final Cut Pro installation. This seems to work fine, I now see all kinds of IMX options under the Video Codec section in Quicktime export, but there is one problem...
There is no way to edit any codec settings to turn off Quicktime Gamma correction, as you can do if you are exporting to Apple ProRes. What happens is - I need to add a Gamma Correction filter to every timeline to make it darker, because the default encoder settings automatically include some gamma correction that makes all rendered videos slightly brighter than they should be. This is a bit annoying.
Does anyone know if there is a way to disable Gamma Correction for MPEX IMX Quicktime files? Also, when will Adobe include native MPEG IMX encoder support? A lot of broadcasters in Europe (especially Eastern countries) still use IMX as their codec in their playout facilities - sometimes in Quicktime containers and sometimes in .mxf containers. Premiere needs to supports this.
Thanks!

Hi JS,
Thanks for the reply.
I can do but they're big files (about 2 to 3 gigs each - long takes!) so would take a while. I'd have to do it tomorrow now coz they're on a hard drive at the office.
John

Snow Leopard's Default Gamma & Color Correcting for Pre Press in Photoshop CS4

After searching the forums I thought I would start my own thread on this subject.
I have Photoshop CS4 and InDesign CS4 and I have continued to color correct, for pre press, in OS 10.4.11 Tiger with the 1.8 Default Gamma and 6500 color tempurature, using Apple's display calibration tools in the OS's System Preferances.
I want to switch to Snow Leaopard but with it's Defualt Gamma of 2.2, I'm not able to make my minitor manually adjust to the needed range for brightness and contrast that is needed to begin the calibration process. Is there a way to color correct photos, for pre pre press, in Photoshop with a 2.2 Gamma setting in my display preferances?

I have had success just with Apple's System Preferences for color calibration. I do design and pre press for a number of customers of the various printers I work with. Most of the photos I work with are from digital cameras and are provided by the customer. The only point in the whole process, where the photos get adjusted to have eye pleasing color, when coming off the printing press, is when I work with them.
The printers I work with continue to send their customers to me, for design and pre press, because they like my color work on the photos. I send the pre press files as Press Optimized PDFs to the printer's FTP server and the printer does all the direct to plate separations in-house. I want to continue to be reliable in that area and so the brighter default Gamma built into Snow Leopard seems to complicate things if I ever want to move up from Tiger to Snow Leopard.
I have two 17" Apple CRT displays that cannot adjust into calibration range when I'm booted in Snow Leopard. These CRT displays can only manually adjust in range for calibration under Tiger or Leopard. It sounds like if I purchase an IPS based LCD monitor, made by Apple, Dell, or other brands, I will probably be able to manually adjust the display for Gamma 1.8, under Snow Leopard.
I was posing this question about using Gamma 2.2 because if I could color correct for pre press with the 2.2 setting, I could continue to use my old Apple 17" CRT displays and also any web content I create will preview closer in color, on PCs as they will on my Mac. Maybe my review PDFs will view with similar color on my customers PCs if I work with a 2.2 Gamma setting and instead of 1.8. For now I know I will keep my printers happy if I continue to work with a monitor that has a 1.8 Gamma setting and a 6500 color temperature setting. If that must continue to be the standard for pre press, then I will need to get an IPS based LCD monitor that will allow me to adjust in the 1.8 Gamma range while booted in Snow Leopard.

FCP Gamma Correction

This isn't something that can really be answered, I just wanted to vent a little frustration about the way Apple handle the display gamma with FCP.
From my understanding, Apple assume (and advise) that monitors are set to 1.8 gamma when running FCP, video shown in the viewer and canvas windows is then shown darker to resemble a 2.2 gamma which is how most other computer users see it, although the actual footage remains unaffected.
That's all well and good, except that I use a 2.2 gamma already because I want to see content in the same way as the majority of computer users in all my apps, and because FCP is making the video look darker I'm no longer seeing realistic results when using it. Apples recommendation to use a gamma of 1.8 to get around this seems like madness to me, why can't the gamma correction be turned off in the FCP user preferences?
At the moment I have to export quicktime files and view them outside of FCP to see what they really look like without the fake gamma correction, and then blindly make adjustments in FCP and repeat the whole process until I get the result I'm looking for - hardly a good way of working.
Apple, please give us a check-box in the preferences to stop this forced gamma change.
Paul.
Message was edited by: Videotrader

Hi Fergus
If your concern is regarding the gamma calibration of your apple display then open up the OS X System Preferences > Dsiplays pane, Choose the Color tab for the appropriate monitor and press the Calibrate button ... in the first window of the Display Calibrator Assistant don't turn on Expert Mode, just press Continue, the very next screen allows you to set the target gamma, either the Mac OS standard gamma setting of 1.8, or the PC/TV standard gamma setting of 2.2 ... step through the remaining settings and save / use your new calibration profile.
As to your actual question ... go to admit that I don't know mate! But if FCP does indeed make adjustment for your display gamma settings, it will do it with reference to your displays calibration.
All that said, your gut instint is correct, you should NOT be using your apple dispaly for making critical color correction decisions. It's totaly wasting your time. You can only make reliable critical color correction decisions when using a properly calibrated reference monitor
Hope that helps
Andy

Best rgb and gamma settings for external monitor with mountain lion

Hi,
I'm using an LG LED 22 inch monitor with my MBP mid 2010 via minidisplay to hdmi. on OS X side the settings have been default. On the LED side the settings , if set to preset RGB it tends to fade the whites a lot. when i set to user definied and let the preset rgb be at it is, the colors are quote decent. currently they are on R 50, G 58 and B 59 and Gamma 1. Which is the best RGB and Gamma value for OS X Mountain Lion?

Welcome to the forum.
First off, you need to go and buy a hardware monitor calibrator, such as an OptixXR or similar. This will build a custom monitor profile for your specific screen. Without this starting point you can forget ANY attempt at accurate colour matching.
Never (and I mean never) use a working space such as sRGB or Adobe98 as your monitor profile, that's not what they are designed for. Working spaces control what colours are possible in the image, monitor profiles control how those colours are shown on screen. Aperture uses it's own working space so you don't have to worry about that too much.
To answer the rest far too briefly, I'd suggest setting the proofing profile to sRGB and of course use sRGB for the export preset. The gamma setting you will have to adjust depending on how dark the Lightjet prints look compared to your screen. You will have to do test-strips to start with.
Your images looking crap on flickr on Windows machines is partly because Windows web browsers generally do NO colour correction, and only partly to do with the different gamma.
Ian

Why Levels mid-point slider and Exposure Gamma Correction slider not the same?

Both the mid-point slider in Levels and the Gamma Correction slider in Exposure adjustment appear to modify Gamma. They even use the same numeric scale.
When Gamma <= 1, both sliders appear to produce the same results (confirmed with a couple of random sample settings and using the Difference blend mode).
When Gamma > 1, however, the results are very different. Levels produces more what one would expect in terms of moving the Gamma curve without moving the white and black points but the Exposure Gamma Correction slider seems to do something very different, either moving the black point or applying a very different curve the produces much brighter tones in the dark shadows.
Can anyone explain why and how these two adjustments produce different results?
Is this a bug with the Exposure adjustment?
By the way, in my limited tests of this I was just using a standard RGB file in 16-bit mode - nothing fancy like 32-bit or LAB or anything like that. Also, Photoshop CS6 Extended. Both 32- and 64-bit versions show the same behavior.
Thanks.

The differing gamma adjustment results also occur in the OS X version of Ps 13.0.1
The situation is worse than you realize, Dennis. Test with a linear grayscale gradient in 16-bit or 8-bit RGB mode instead of arbitrary images. Remember to view at 100% zoom for an accurate display.
Gamma adjustments of less than 1 performed by Levels adjustment layer and Exposure adjustment layer do differ but to a less obvious extent than when the adjustment is greater than 1. Differences can be seen in histograms, and low level differences when differencing layers can be made more obvious by adding an Exposure adjustment layer with the exposure increased.
You'll get further different results by using the gamma adjustment in the "Exposure and Gamma" method of Image > Adjustment > HDR Toning. Notice that the gamma value there has to be specified as the inverse of that in Levels and Exposure.
I haven't bothered to calculate which, if any, of the three gamma adjustment controls gives correct results because that is Adobe's responsibility.
It's quite ridiculous that a common routine giving consistent and correct results isn't being used for all these gamma adjustments. Code re-use makes software more robust, simpler to test, simpler to correct, leaner and overall easier to manage. But what do I know.

Gamma Correction - always necessary (?)

Has anyone else had a problem with their gamma curves being seemingly whacked after going through Compressor for DVD? I've been dealing with this for the last three years and haven't seemed to find anyone else on the web with the issues I've got. Maybe I'm seeing things.
I've been working with Varicam and XDCAM HD footage primarily. I've found that every time I export to m2v without any Gamma Correction filter adjustments, the video looks more milky and faded when viewed in the DVD Player application (after going through DVDSP) compared to the way it looks in FCP. But the m2v file looks fine when playing it though QuickTime Player. When I apply a Gamma Correction filter in Compressor to compensate for this milkiness, I get a great picture in DVD Player, but in QuickTime, it looks a little dark.
Am I compensating for something I don't need to be compensating for? The reason I feel like I need to be compensating is because when I play regular store-bought movies on DVD Player, they don't have the same milky look in their blacks as I see in my exported files. And I know I'm not supplying milky footage because my deepest blacks are at or very near 0 IRE, and it looks great in FCP and QuickTime.
Anyone know what's going on? I've had this problem through all generations of FCP/Compressor/DVDSP that I've worked with for the last three years or so.
Is the problem really just with DVD Player and I'm worrying over nothing?

Hi! I have experienced the same issues. I so happy i finally found one person with the same problem. I have also used the gamma correction and i am pretty happy with the results. As to why i get this milkiness, i have no idea. I am afraid of actually using this gamma correction thing, because i feel my settings are feirly random at times. How much do you normally correct?
Anders Holm

Final cut pro gamma correction

Hello.
I bet people have posted this before but after searching I could not find a concrete answer.
I have FCP 6 and Color 1.5. My display gamma is at 2.2. I edit my cut in FCP and send it to color. No problems there. I color correct in color and it looks good. I render out a quicktime. Then send the sequence back to FCP. The FCP previews it really dark. I can't do anything to change that. I go to check the rendered quicktime and it's fine, looks the same as color. If I render the final out of FCP it's also dark. This is kind of driving me crazy. Can anyone help?
Thanks.
Joey

Not that I know of. They aren't designed that way. Color is designed to send a proper signal to an external monitor. FCP is just there to show you the picture, the best it can, so that you can edit. Neither are designed for color correcting for the web.
Shane

Console to GUI, Gamma correction Woes

Is there any way in Linux that I can make gamma adjustments in an application basis? Switching between dark console fullscreens to a bright white browser window as fast as hitting a key combination is killing me! (I'm using i3).
I'm not sure I will be able to handle it. However I cannot make global gamma adjustments because that will damage the contrast of the console, and very few X applications include gamma correction settings (I only found one so far, Links2).

Currently I'm using xgamma on a couple of scripts. One of them restores to my normal settings, the other sets a darker screen. I bind the scripts to a couple of keys on i3. This works fine, but I was hoping for something more automatic.
The difficulty in hooking to an application is that I've set the browser to open on another workspace, so xgamma kicks in and I may not even want to go to the browser just yet. I also can't seem to find a way to bind the xgamma action to the changing of workspaces (that would in fact be the ideal solution), so switching back to a darker workspace doesn't restore the gamma.

Question about gamma correction

I recently ordered prints from iPhoto that came directly off my Canon EOS Rebel XT (at max quality). The resulting photos looked very much as if they were printed at PC gamma correction rather than at Mac gamma.
Is there something else I need to set in iPhoto to get the gamma I expect?

Catherine:
Welcome to the Apple Discussions. Do you have your monitor calibrated so the 2.2 gamma? I've done that and prints now look more like the monitor presentation. I've set the monitor to the sRGB profile with the 2.2 gamma.
Do you Twango?
TIP: For insurance against the iPhoto database corruption that many users have experienced I recommend making a backup copy of the Library6.iPhoto database file and keep it current. If problems crop up where iPhoto suddenly can't see any photos or thinks there are no photos in the library, replacing the working Library6.iPhoto file with the backup will often get the library back. By keeping it current I mean backup after each import and/or any serious editing or work on books, slideshows, calendars, cards, etc. That insures that if a problem pops up and you do need to replace the database file, you'll retain all those efforts. It doesn't take long to make the backup and it's good insurance.
I've written an Automator workflow application (requires Tiger), iPhoto dB File Backup, that will copy the selected Library6.iPhoto file from your iPhoto Library folder to the Pictures folder, replacing any previous version of it. It's compatible with iPhoto 08 libraries. You can download it at Toad's Cellar. Be sure to read the Read Me pdf file.

Printing and Gamma correction

I read somewhere in the aperture manuals to match the monitors gamma in prints you may need to set gamma correction to 1.1 or 1.2 in the print dialog.
If I am exporting prints to a pro photo lab am I likely to need to correct the gamma of the exported image or should I send it uncorrected?
Also, should I generally have black point compensation on or off?

I've this code :
short[] threshold = new short[256];
for (int i = threshold_level; i < 256; i++)
threshold[i] = (short) i;
BufferedImage dest = new BufferedImage(source.getWidth(),source.getHeight(),source.getType());
LookupTable look = new ShortLookupTable(0,threshold);
BufferedImageOp buff = new LookupOp(look,null);
buff.filter(src, dest);but I don't know what it's really change, if it's the input level of the BufferedImage, the gamma, the twice...
So to compare I used a commercial Software and I seen that my result is corresponding to a change of the input level of my BufferedImage and a gamma correction too. But i just want to change the input level of my BufferedImage, but I don't find example wich does that, so I try to make a gamma correction in the aim of cancel the first gamma correction produce by my LookupTable.
I hope you understand me. The aim is to make an histogram modification of a BufferedImage.
thank you

Gamma Correction

I have a large number of family photos which I have scanned and stored as TIFF files. Now that I come to print them, I have found that the gamma needs correcting on all of them to make the prints come out right on the printer I have (Canon MG6300). Is there any software, Adobe or any other, suitable for this job?

No, gamma correction can't be done simply by adjusting brightness and contrast. I have videos that are too dark, and increasing the brightness only changes them from murky black to murky gray. But when I saved a still frame and looked at the image with the Mac's "Preview" application, whose Image Correction tool includes a "gamma" adjustment, I found that I could expand the range of black shades to approximate a decent-looking picture. Try it yourself and you'll see what "gamma" does.
MPEG Streamclip is a good program, though. I've used it to fix videos with faded color or poor contrast.

Immediate work available for expert CP5/LMS developer (AEST time zone)

[FRIENDLY MODERATORS - Please move this post to "Work Opportunities" thanks]
We have some modules developed in CP5 that are complete and working fine but need to be integrated with a 3rd party proprietary LMS. The course results are not being reported as expected in the LMS and the situation is urgent. I need someone to work on this fulltime until resolved. Top rates.
Requirements
Australian/NZ based - you'll need to troubleshoot with our client based in Australia during normal AU working hours. If you're outside AEST time zone, it simply won't work
Must have expert in-depth experience in Captivate 5 around quiz and reporting integrating into various LMS. Development/scripting skills may be required above and beyond basic CP.
Urgent - immediate start
Top rates
Don't bother asking what the LMS is, it is obscure, but it is SCORM compliant and does apparently report correctly for Articulate files.
All details will be revealed to the best candidate.
Email me directly: [email protected]

Hello,
Forum has only one moderator: Captiv8r (Rick Stone), perhaps try to ask him by private message?
Lilybiri

Help with Gamma correct rescaling

So apparently Photoshop does not correctly account for Gamma when re-scaling an image, which can change the overall brightness in a noisy image:
http://www.4p8.com/eric.brasseur/gamma.html
http://www.kiransprojects.com/blog/2014/photoshop-blending-is-broken/
Is there any kind of solution in the works? Scaling does the right thing when working in 32-bit mode, but when creating things like textures for games, most work is in 8-bit mode, so switching to 32-bit mode every time I need to resize my image is not feasible.

Exactly! in a default 8-bit image the colors are gamma encoded, but when Photoshop re-sizes the image it treats it as if it was a gamma 1.0 image.
So if I have an image that has a lot of high frequency details like this UI bar:
if I then scale it down in Photoshop (which I would do if I was making an IPhone app that needed retina and non retina images, or if I just like making my images at a higher resolution and then scale them down when finalized), I get this:
when I should be getting this:
I got the second image by turning my image to 32-bit mode and then re-sizing it, which preserves the brightness in the blue area. The difference is subtle, but here is a side-by-side:
The first one is when re-sized in 8-bit mode, the second one is re-sized in 32-bit mode. you can tell that the image on the right preserves the brightness of the blue part, while on the left it gets darker.
In most cases the effect is not noticeable, but in some cases it can be very destructive on small patterns. I think most people who use Photoshop don't understand or care about the difference, but when I've explained it to my co-workers, they all agree that the expected behavior is that re-sizing should preserve the visual brightness of the image. At the very least there should be some sort of option to do gamma corrected re-sizing in 8-bit mode.

Sorting not working correctly for date field in alv report

Hi All,
My report displays many rows also containing date type fields of bldat,budat .
When I sort the report selecting field of type bldat budat the sorting is not correct for the year.
Ex:
Invoice doc dat
01-25-2011
01-21-2011
02-02-2011
10-25-2010
11-20-2010
If I use ascending then it is sorted as :
Invoice doc dat
01-21-2011
01-25-2011
02-02-2011
10-20-2010
10-25-2010
Why the sorting is not working correct for year.(2010 records should have been first).
The field wa_tab-bldat is of type char10.
It is populated as wa_tab-bldat = bsak-bldat.
Kindly suggest what can be done.

The field wa_tab-bldat is of type char10
Then what it does is correct.
Refer to type datum...it will work

VF0070 gamma correction - for experts...

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