Topic: Canyon Conumdrum

[Greg Groess]

Mike has asked me to shoot the image from a canyon that cannot be improved in LAB. 
I know you all love a good challenge. 
My best result is in RGB so far....
This image was shot at sunset it is a lengthy exposure....

Give it a shot...

Greg

[themightyzog]

I think you need a course in exposures!! - only joking Greg.

This is not the day to post a challenge and say Lab is impossible.

Just a quick fiddle only in Lab - I'll try later in the week when I have time as this is persumably not the effect you are looking for!

Chris

[ianbowie]

Greg,

My shot at it in Lab only.

Ian

[Greg Groess]

The rock in the foreground is too blue.....Try it in RGB and set a reasonable neutral and you will see what I mean...

Mike's challenge to me was..."go on vacation and try to shoot an image of a canyon that cannot be improved in LAB."

90+ percent of the images I shot last week can indeed be improved in LAB...I found this one to be a real problem child...I will post my RGB later this week....

Greg

[ianbowie]

Greg,

I see what you mean ..... second try.....

[derekfountain]

The rock in the foreground is too blue.....Try it in RGB and set a reasonable neutral and you will see what I mean...

Mike's challenge to me was..."go on vacation and try to shoot an image of a canyon that cannot be improved in LAB."

90+ percent of the images I shot last week can indeed be improved in LAB...I found this one to be a real problem child...I will post my RGB later this week....

Greg

What are the characteristics of an image that make it unsuitable for correction in Lab mode?

[Greg Groess]

Well for me it has been the fact that no matter what I do to it I cannot make it look like it should.  I cannot get rid of the yellow green cast when I set a single neutral. 

It can be improved but When I use RGB I get much... much better results.

Greg

[derekfountain]

Well for me it has been the fact that no matter what I do to it I cannot make it look like it should.  I cannot get rid of the yellow green cast when I set a single neutral. 

Here's my fix. I also couldn't get anything decent looking from lab mode. Looking closely at the image with the aid of the hue clock, you can see there's a blue cast which gets deeper as the tones get darker. I think that's the key; the CM help text says that RGB is good at fixing problems where a colour cast is associated with a change in brightness, and that's exactly what we have here. I can't claim to understand the theory why that's true, but the curve shown below does get a decent result.

After the colour fix with RGB mode, I added another conventional pass in Lab mode to lift the brightness and increase the saturation. It's actually possible to lift the brightness to the point where it looks like a daylight shot, but since it was a long exposure sunset shot I tried to keep it a bit dark and saturated, like perhaps the view appeared at the time.

[Greg Groess]

Derek,
That is where I got it in RGB as well...I like this one so far....

Greg

[themightyzog]

I think that is absolutely excellent Derek,

I'm puzzled by one thing - I tried to copy your curves to see what was going on, and I noticed that I could not get the histograms to be anything like yours (see below), especially the red and green channels - so I guess you did at least 3 passes.  The first to lighten, then RGB, then Lab - is that right?

I had this problem on the course where I could not get my histograms to look like other people's - Mike suggested the difference between precise mode being on/off.

Does anybody else have this problem with histogram representation?

Thanks
Chris

[derekfountain]

I'm puzzled by one thing - I tried to copy your curves to see what was going on, and I noticed that I could not get the histograms to be anything like yours (see below), especially the red and green channels - so I guess you did at least 3 passes.  The first to lighten, then RGB, then Lab - is that right?

No, 2 passes, of which 90% of the image correction happened in the first RGB pass. I put a shadow point in the darkest rock at the very left of the image and a neutral on the large whiteish clump of rock in the foreground. I couldn't find a highlight. I then moved the neutral around a bit to find a sweet spot I was happy with - there's no 'right' answer here I don't think. That was the basic correction which got the blue cast out and the reds and yellows looking as I wanted them. On top of that I manually added the slight boost in the RGB curve highlights. From there I had another pass in Lab mode to boost the lightness and saturation.

I can honestly say I hardly ever look at the histogram. I find the direct feedback from the image, together with the stand alone Hue clock, give me all the information I ever use.

[themightyzog]

I am absolutely lost with trying to understand the difference between the histogram representations.

If I follow your curves and then Lab adjust, I can get your rendition Derek, but what ever I tried I could not load an image that gave angthing near your channels.

So either you are opening the image in a colour profile I never use (I tried nought, RGB & sRGB), but surely profiles will make no difference to a histogram?
Or the different versions of CM show different results.

I know some people do not use the histogram at all - is this because it is just so unreliable I wonder?

Here is an image of CM and Reindeer's idea of the blue channel - PS itself was useless as the top of the peaks were out of range!

Mike, Greg - can you throw any light (!) on the problem?

Thanks
Chris

[Greg Groess]

I think you need a course in exposures!!

I think that is absolutely excellent Derek,

I see how this is going to play now....sure.....i get it....

I love to parse sentences.....LOL

Good job both of you.....
Greg
P.S. the histogram technology is Mikes bag...I'm gonna let him explain it to me as well...

[themightyzog]

re histograms - I did a little more testing and they come out differently depending on the mode of the image before CM is opened!

But still the peaks do not agree with other representations.

I would have thought that it is simple matter to add up the values to get a histgoram, but something else must be going on!

What's the answer Mike?

Chris

[derekfountain]

What's the answer Mike?

Perhaps more to the point, what's the question? What are you trying to achieve with the histogram? The only reason I ever look at a histogram in Photoshop is to see whether there's an empty area at one or both ends, which tells me the image isn't using the entire tonal range. I always use the histogram on my DSLR to check exposure, and I use it in RAW conversion, again to check exposure. But once in Photoshop I rarely pay it any attention.

Under the CurveMeister settings, there's an option to turn the histogram on/off. What happens to your workflow if you uncheck that box? It's not a flippant question! What are you getting (or trying to get) from the histogram that I'm missing? (Apart from hassle and trouble?)