Author Topic: Darker or lighter in PS or website  (Read 4123 times)

Offline Emanuele

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Darker or lighter in PS or website
« on: 2010 August 22 14:46:40 »
I have a quick question:
when I process and image and save it as 16 bit Integer and then open the image up in Photoshop, the image is always either much darker or much lighter.
I bring the image in Photoshop because of the Signature and Frame around the image.
But why does that happen?

How can I make sure that the colors and background are the same?
Even when i put it on my website it shows darker or lighter.
I assign the ICC SRGB 4 Profile to the image always, but do not embed it in the image.

Thanks,
E.

Offline Niall Saunders

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Re: Darker or lighter in PS or website
« Reply #1 on: 2010 August 22 15:17:44 »
Hi Emanuele,

Are you saving as a FITS Integer file format?

Cheers,
Cheers,
Niall Saunders
Clinterty Observatories
Aberdeen, UK

Altair Astro GSO 10" f/8 Ritchey Chrétien CF OTA on EQ8 mount with homebrew 3D Balance and Pier
Moonfish ED80 APO & Celestron Omni XLT 120
QHY10 CCD & QHY5L-II Colour
9mm TS-OAG and Meade DSI-IIC

Offline Emanuele

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Re: Darker or lighter in PS or website
« Reply #2 on: 2010 August 22 15:23:58 »
Niall,
I am saving as Tiff, 16Bit integer when I pass to Photoshop....

Offline Niall Saunders

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Re: Darker or lighter in PS or website
« Reply #3 on: 2010 August 22 15:31:29 »
What happens if you save as a JPG (with or without an embedded ICC profile) - and save as maximum quality

I don't see any advantage in transferring as a TIFF - by this stage you now have your image diaplaying on the PI workspace (without an STF) in its 'best possible' format - which means that you now have the image 'optimised' for 8-bit display.

Save it in FITS 32-bit format first - you should always do this, because this would be your 'working' data. Then re-save as an 8-bit 100% quality JPG.

See the attachment.

Cheers,
Cheers,
Niall Saunders
Clinterty Observatories
Aberdeen, UK

Altair Astro GSO 10" f/8 Ritchey Chrétien CF OTA on EQ8 mount with homebrew 3D Balance and Pier
Moonfish ED80 APO & Celestron Omni XLT 120
QHY10 CCD & QHY5L-II Colour
9mm TS-OAG and Meade DSI-IIC

Offline Juan Conejero

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Re: Darker or lighter in PS or website
« Reply #4 on: 2010 August 23 12:10:53 »
Hi Emanuele,

It sounds like you have a color management issue in your imaging workflow. Think of color management as a chain that connects your pixels with the physical device that is going to reproduce your image (a monitor in this case): if a single link is broken, the whole chain ceases to work.

Follow these steps to reset your color management settings:

1. If you have calibrated your monitor with a hardware or software device, be sure your monitor has the appropriate ICC color profile assigned on your operating system (Windows I guess). If you haven't calibrated your monitor, then be sure you have the 'sRGB IEC61966-2.1' profile assigned to your monitor. If you haven't calibrated your monitor and your monitor's manufacturer has published an ICC profile for your monitor model, use it instead of sRGB.

2. In PI, select Edit > Color Management Setup. You should see the correct monitor profile on the ColorManagementSetup interface. This is selected automatically upon PI startup and you cannot change it. Click the Reset icon (bottom right corner) to make sure you have all the default options. On ColorManagementSetup, now you should have the 'sRGB IEC61966-2.1' profile selected as the default profile for both RGB and Grayscale images.

3. Click the Apply Global icon (blue sphere) or press F6. Now you have set the default color management options in PixInsight.

These are general guidelines to export images for printing or to open them in other applications:

- If you are exporting a JPEG image for the WWW, you should:

* If necessary, convert pixel values to the sRGB space using the ICCProfileTransformation tool. This is only necessary if your image has a profile embedded different from sRGB, or if it has no profile embedded and you have selected something different from sRGB as your default RGB profile (see step 2 above).

* Don't embed an ICC profile in your JPEG image for web deployment. Most browsers don't work correctly when an image has a profile embedded.

- If you are exporting a TIFF image to use it with other applications that support color management:

* Always be sure that your TIFF image has the correct profile embedded. The correct profile is the default RGB profile (step 2 above) if the image didn't have an original profile embedded (as happens when you start with a raw CCD image for example).

- If you want to print your image:

* If you're printing with PI, select File > Printer Color Management and be sure you have the correct ICC profile selected for your target printer. Read the tooltips as they provide important information.

* You should use PixInsight's color proofing and gamut warning functions to verify how your final printed result will look like. The gamut warning feature will show you which pixels will get clipped because they are out of your printer's color space, so that you can fix them (by decreasing color saturation, usually).

Hope this helps.
Juan Conejero
PixInsight Development Team
http://pixinsight.com/

Offline Emanuele

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Re: Darker or lighter in PS or website
« Reply #5 on: 2010 August 23 15:03:00 »
Niall: thank you for your help. I will do as suggested.

Juan: wow, thank you so much :) I have copy and pasted your post in my notes application and will follow step by step the procedure you have described. My monitors (iMac 24" and MacBook Pro 15") are both calibrated using the DataColor Spyder 3 Pro.