Boy thats a big topic. Im pretty sure but not positive that Joseph has a movie on Colour Correction. Definitely check that out. Pre-press shops go by the numbers meaning they understand that Grey or Gray (depending if you are British or Canadian) is made with equal parts of RGB. Knowing that you can find a grey in most shots and use Apertures eye dropper to neutralize it is the start. You may want to adjust the results based on the existing lighting, to get back to capturing the atmosphere (ambiance if you are french). Sunset shots should look warm …how much warmth is your subjective call.

There is a lot on this so hopefully the other will chime in. Hope I wasn’t too cheeky.
Cheers
DBM

Arron
Definitely check out all the videos on this site first for the best info on Aperture and colour.

Here are two resources that I have used. The first is tough to get through because he is from the Prepress industry and uses CMYK. If you are not thinking of converting to cmyk for offset printing you might like the other resource. Dan has Videos on Kelby’s Napa site,where Dan is talking about his “Picture Postcard” technique, which is more RGB. If you have to shoot a stack of towels or sweaters and the colors have to be perfect then you need prepress knowledge. Hint each towel, sweater shirt and shoe in a catalog is mask with the Pin Tool, (not the Tragic/Magic Wand) and has had curve layers applied to each specifically. A towels highlights will get different curves that its shadows. (Oh god I’m bored now)

If you are more of a portrait Photographer Lee Varis talks a lot about correct color of Skin in his 2 books using RGB numbers. Not easy to do but his examples make it look easy. He has Videos on Lynda.com

I have a grey card in my bag and sometimes use it. Most the time I look for something in the shot that is Nrutral Black white or grey and use the WB tool in AP3 to bring it into balance (equal parts RGB 128,128, 128 or any equal set along the scale of 0-255) That most likely changes the Temp slider a lot and I then find a subjective balance between the before and after. 3/4 of my work is editorial so color subjectiveness is ok, 1/4 is more geared for accurate Prepress.

1 Professional Photoshop: The Classic Guide to Color Correction (5th Edition) Dan Margulis

2 Skin: The Complete Guide to Digitally Lighting, Photographing, and Retouching Faces and Bodies by Lee Varis

First step Calibrate your Monitor.

Cheers

David said :

If you have to shoot a stack of towels or sweaters and the colors have to be perfect then you need prepress knowledge.

.

I totally disagree with this.  :) :)

The whole point of colour management, is to make this sort of skill … simple. Well … simpler.

If you have a properly profiled setup, then the entire reason that the icc system exists is to achieve exactly this sort of scenario, without relying on the knowledge and skill of an offset printer.

The truly amazing/fantastic/incredible thing about colour management, is ‘convert to profile’. That, in a nutshell, is what it is all about. Using ‘Perceptual’ conversion for cmyk is the truly stunning bit. (It’s stunning of course, only for those of us with a long time knowledge of what happened before colour-management.) So what happens when you do this?

Well … you have your towels and are working in RGB and you want to send the file to your offset printer. Perceptual conversion will take all of the colours and re-map them, into a different colour space, so that they ‘look’ as similar as possible. This entails the software doing some incredibly complex things. Essentially, it is taking colours that are outside the capabilities of the offset and mapping them to alternative colours, that are inside the offset’s capabilities. This could be a simple ‘nudge’ to a neighbouring pixel, or a considerable shift, which when all is said and done … will ‘look’ the same … or very close. It has to take into account any sudden ‘leaps’ that are too extreme, because they will cause banding and it has to consider the overall look. Unbelievable really.

Anyway …

If you want to get your towels really accurate, the best way would be to work in a consistent lighting setup and to create a profile for that setup using a MacBeth chart. This was brought to the larger market 2 or 3 years ago, with passport, but I’ve been using this for 12 years with high-end MF-Digital-Backs from Jenoptik. Basically, the capture software for my MFDBs will apply a wide-gamut profile created from a MacBeth, including a ‘shading’ correction, so that I get … according to the numbers … a very accurate, true to life, colour file.

Now that I have that file, the process of converting to cmyk relies simply on whether or not I have a correct profile for that cmyk device. Offset printers are very reluctant to make their business appear simple, so getting any kind of profile out of them is a hard task … but … with a huge investment in digital-offset starting to take hold in the industry … their grasp is getting weaker. So if you have that profile, moving your image to their offset press, is as simple as performing the ‘convert to profile’ step.

If you don’t have a cmyk profile the you can always get one by having your offset printer do a standard test print/ouput of a patch-chart you supply them with, from a profiling hardware/software combination, then use your profiling hardware to scan and build a profile for that press.

Grant

Grant I was trying to stay away from the topic of color management and just talk of basic color correction. I do like hearing of all your experience and knowledge. I found when I did build camera profiles for the Sinar53 that the prepress people in the next room still built individual paths for for each article of clothing or product in the shot and tweaked them with unique curves. They would do about 6-7 creo proofs before they called a page done. Really glad Im shooting more editorial now, less stress but less money.

So Back to the topic …. Say you got an image from someone on the list here that needed help in color correction. How would you approach evaluating and adjusting it at that point? Using Aperture tools!

David,

the term ‘colour correction’ implies that there is something that needs to be ‘corrected’. I don’t know what that might be.

Aperture’s colour tools are pretty weak. Very weak really. There is a limited grey balance tool, which Apple call ‘white balance’ and the ‘Color’ brick is incredibly crap. Aperture is not an app that I would use to do any kind of radical colour work.

That said, you can use it for small ‘tweaks’. The ‘white balance’ brick is okay for making an image generally warmer or cooler. I guess this is what Apple had in mind when they made it. The Color brick is vaguely okay for doing some small colour changes on local localised colours, but it’s poorly designed. I think Apple tried to make it simple, but ended up making it useless.

You can use Curves, which can of course do pretty much anything you want in terms of a target colour, but are difficult at best in terms of selections and they require a good understanding of how they work, which is not part of the target audience of Aperture (was it ever?). They’re also very slow compared to a tool that can select a colour and alter only that colour.

The absurdly difficult/imprecise colour circles for tints in some of the adjustments bricks, really do make you wonder about some of the engineering involved in the app.