Fix the wrong CMYK->RGB conversion

Started Oct 19, 2013 | Discussions
PJay Junior Member • Posts: 28
Fix the wrong CMYK->RGB conversion

How to make the first photo to look like the second one? (please see in a browser/photo viewer that supports color management)

http://imgbox.com/aczHRPTJ

http://imgbox.com/adsTc0oz

The first photo is correct but I wanted to know what happened to the second photo that looks wrong.

Is there anyway to fix it?

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion

Both photos are untagged -- not color managed. They are both missing embedded ICC profiles and so the colors in the photos are undefined.

Toermalijn
Toermalijn Forum Pro • Posts: 15,738
Re: Fix the wrong CMYK->RGB conversion

PJay wrote:

How to make the first photo to look like the second one? (please see in a browser/photo viewer that supports color management)

http://imgbox.com/aczHRPTJ

http://imgbox.com/adsTc0oz

The first photo is correct but I wanted to know what happened to the second photo that looks wrong.

Is there anyway to fix it?

They both look the same...

OP PJay Junior Member • Posts: 28
Re: Fix the wrong CMYK->RGB conversion

No, they're not the same if you see it as I said in the first post.

And it's not about the color profile because they have both no embedded ICC profile.

This problem happens while a wrong conversion, the thing I need to know.

For example, if you see the first photo in Google Chrome, it looks like the second one.

This is the exact thing I need to know how it happens.

I tried to delete the black or other channels of the first photo (CMYK) but no luck

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion
2

PJay wrote:

No, they're not the same if you see it as I said in the first post.

I didn't say they were the same. One is CMYK with all colors undefined and the other is RGB with all colors undefined.

And it's not about the color profile because they have both no embedded ICC profile.

It is precisely about the color profiles because they both have no embedded ICC profile. Your problem is a color management problem. In both these photos all colors are undefined because they are lacking embedded ICC profiles.

This problem happens while a wrong conversion, the thing I need to know.

Converting a photo with undefined colors (no ICC profile) to a different structure photo with undefined colors (no ICC profile) would always be a wrong conversion.

For example, if you see the first photo in Google Chrome, it looks like the second one.

And if you see the 2nd photo in Firefox it looks like the first one.

This is the exact thing I need to know how it happens.

I tried to delete the black or other channels of the first photo (CMYK) but no luck

OP PJay Junior Member • Posts: 28
Re: Fix the wrong CMYK->RGB conversion

Ysarex wrote:

And if you see the 2nd photo in Firefox it looks like the first one.

The 1st photo, you meant since the 2nd photo looks the same everywhere (RGB 24bit)

Yes, it's the thing I need to know: How to make the first photo to look like the second one?

Both Firefox/Chrome could do that wrong conversion with CMYK but I couldn't do anything in Photoshop or else 

Hope you got my goal 

(unknown member) Forum Pro • Posts: 10,011
Re: Fix the wrong CMYK->RGB conversion

PJay wrote:

This problem happens while a wrong conversion, the thing I need to know.

Here is what you need to know: There is no right way to convert from CMYK to RGB. Don't do that.

Do. Not. Do. That.

Treat RGB > CMYK as a one-way street. Once you get to the CMYK end, you're there to say. Don't go back. Ever.

-- hide signature --

~ Peano
www.radiantpics.com

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion

PJay wrote:

Ysarex wrote:

And if you see the 2nd photo in Firefox it looks like the first one.

The 1st photo, you meant since the 2nd photo looks the same everywhere (RGB 24bit)

The 2nd photo does not look the same evertwhere.

Yes, it's the thing I need to know: How to make the first photo to look like the second one?

Do you want the CMYK version to look like the RGB version or do you want the RGB version to look like the CMYK version?

Do you have an undamaged version of either? A photo without an embedded ICC profile is damaged and it may not be possible to easily fix it. So do you have a version with it's ICC profile still in place?

Both Firefox/Chrome could do that wrong conversion with CMYK but I couldn't do anything in Photoshop or else

Hope you got my goal

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion

Peano wrote:

PJay wrote:

This problem happens while a wrong conversion, the thing I need to know.

Here is what you need to know: There is no right way to convert from CMYK to RGB. Don't do that.

Do. Not. Do. That.

Treat RGB > CMYK as a one-way street. Once you get to the CMYK end, you're there to say. Don't go back. Ever.

Entirely agree -- I wasn't sure that's even what's the OP is up to here but I suspected as much.

PLay: Peano is correct and that begs another question: Unless your about ready to ink your press what are you doing with a CMYK photo in the first place?

benross Senior Member • Posts: 1,013
Re: Fix the wrong CMYK->RGB conversion

Interesting!

On my Mac (colour managed) I opened both pictures with Safari and Chrome. In Safari CMYK file is clearly different from RGB one. In Chrome they both look like the RGB file.

If you want the first one to look like RGB file, then why make it in CMYK colour space? I don't quite understand.

The monitor is in RGB space anyway. So when Safari encounters a CMYK file, it tries to 'simulate' what it'd look like (a reflective surface) in RGB space.

I think Safari 'simulates' CMYK file in RGB space, and Chrome 'corrects' it for RGB space. Both Safari and Chrome clearly manage the colour, they seem to have differences in 'philosophy'!

OP PJay Junior Member • Posts: 28
Re: Fix the wrong CMYK->RGB conversion

Ysarex wrote:

PJay wrote:

Ysarex wrote:

And if you see the 2nd photo in Firefox it looks like the first one.

The 1st photo, you meant since the 2nd photo looks the same everywhere (RGB 24bit)

The 2nd photo does not look the same evertwhere.

Yes, it's the thing I need to know: How to make the first photo to look like the second one?

Do you want the CMYK version to look like the RGB version or do you want the RGB version to look like the CMYK version?

Do you have an undamaged version of either? A photo without an embedded ICC profile is damaged and it may not be possible to easily fix it. So do you have a version with it's ICC profile still in place?

Both Firefox/Chrome could do that wrong conversion with CMYK but I couldn't do anything in Photoshop or else

Hope you got my goal

It's strange because your second photo in Photoshop looks much more saturated than mine, maybe you set another default profile like Adobe RGB?

But you're totally right!

Well, I tried to open CMYK in XnView and it converted to RGB 24bit as soon as I opened it.

Then I got the same color like the 2nd photo or the first photo in Chrome. Even the ICM was enabled in XnView.

Next, I embedded "CMYK, U.S. Web Coated (SWOP) v2" ICC profile to the first photo then I noticed that XnView (with ICM enabled!) converted it right like Photoshop or else.

So each program must use a profile to convert CMYK<->RGB

Now would you tell me what photo will have the right color on RGB Monitor?

And what photo should I use to print? the CMYK one?

Before, I thought the CMYK version has the right color but now it seems without profile, it's damaged too.

Unfortunately, I have no other version, only those two

And really thank you all to help me <3

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion

PJay wrote:

Ysarex wrote:

PJay wrote:

Ysarex wrote:

And if you see the 2nd photo in Firefox it looks like the first one.

The 1st photo, you meant since the 2nd photo looks the same everywhere (RGB 24bit)

The 2nd photo does not look the same evertwhere.

Yes, it's the thing I need to know: How to make the first photo to look like the second one?

Do you want the CMYK version to look like the RGB version or do you want the RGB version to look like the CMYK version?

Do you have an undamaged version of either? A photo without an embedded ICC profile is damaged and it may not be possible to easily fix it. So do you have a version with it's ICC profile still in place?

Both Firefox/Chrome could do that wrong conversion with CMYK but I couldn't do anything in Photoshop or else

Hope you got my goal

It's strange because your second photo in Photoshop looks much more saturated than mine, maybe you set another default profile like Adobe RGB?

But you're totally right!

Well, I tried to open CMYK in XnView and it converted to RGB 24bit as soon as I opened it.

Then I got the same color like the 2nd photo or the first photo in Chrome. Even the ICM was enabled in XnView.

Next, I embedded "CMYK, U.S. Web Coated (SWOP) v2" ICC profile to the first photo then I noticed that XnView (with ICM enabled!) converted it right like Photoshop or else.

So each program must use a profile to convert CMYK<->RGB

Now would you tell me what photo will have the right color on RGB Monitor?

And what photo should I use to print? the CMYK one?

Before, I thought the CMYK version has the right color but now it seems without profile, it's damaged too.

Unfortunately, I have no other version, only those two

And really thank you all to help me <3

In reference to Peano's comment earlier; not only is it wrong to try and convert a CMYK photo to RGB it is also wrong to create a CMYK photo or attempt to use a CMYK photo for printing unless you're printing the photo on a specific offset press the characteristic of which you are familiar with. I think I'm safe to assume that you're not trying to set up a press run on an offset press, so you have no business trying to use that CMYK file.

If you're trying to make a print with a desktop printer or sending out to have a print made by a print service business you should be using a color managed RGB file.

Good luck

OP PJay Junior Member • Posts: 28
Re: Fix the wrong CMYK->RGB conversion

Thank you. Since I found both photos on the web, I think the RGB photo has created from the CMYK one.

So if I want to print, even the CMYK photo will need a profile to look correct, right?

OMG, I have so many CMYK photos without profile and each program shows it different, here's another one:

http://i.imgbox.com/adwdyE5p.jpg

So there's no default profile for CMYK?

Ysarex
Ysarex Senior Member • Posts: 2,293
Re: Fix the wrong CMYK->RGB conversion

PJay wrote:

Thank you. Since I found both photos on the web, I think the RGB photo has created from the CMYK one.

Probably not -- most likely the CMKY was created from the RGB.

So if I want to print, even the CMYK photo will need a profile to look correct, right?

Yes, that and a lot more. You also need a printer profile and a display profile.

OMG, I have so many CMYK photos without profile and each program shows it different, here's another one:

http://i.imgbox.com/adwdyE5p.jpg

So there's no default profile for CMYK?

No. And unless you're printer looks something like this:

you shouldn't have a CMYK file to begin with. If your printer did look something like that odds are you'd know what you were doing.

OP PJay Junior Member • Posts: 28
Re: Fix the wrong CMYK->RGB conversion

Ysarex wrote:

Probably not -- most likely the CMKY was created from the RGB.

I said it because people used to remove all tags in the photos and convert 32bit->24bit with XnView then share it on web.

With converting the CMYK photo to RGB with XnView, I can reach to the second RGB photo I have posted easily.

But I'm not sure what profile XnView uses, I asked them and they said sRGB but it's not for converting CMYK to RGB, right?

Because I tried to embed sRGB to CMYK photo and it looked quite wrong and odd... like inverted

Another reason is that the RGB version has less details in the shadow than CMYK while RGB has greater range.

I don't know what to do with my untagged CMYK photos, I want to print and see them on my monitor correctly

My printer is only Canon MG5120+Ilford paper not like that one

mli20 Regular Member • Posts: 259
Re: Fix the wrong CMYK->RGB conversion

You need to be aware of the difference between:

- Colour Models, like CMYK, RGB

- Colour Spaces, like sRGB

- Colour Profiles, like Canon IJ Color Printer Profile 2006

For example, a conversion between colour models does not per se involve a colour space or a profile.

Cheers, Mogens

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