From: AHFAP, for image professionals in the UK cultural heritage sector [mailto:[log in to unmask]] On Behalf Of Sara Rawlinson
Sent: 11 January 2018 15:00
To: [log in to unmask]
Subject: Re:  Re: Accurate colour reproduction

Hi all,

I, too, am enjoying following the discussion and would be interested in attending talks. 

I am also interested in learning how people assess the end-user problem. Once the camera, computer, and printer are all in agreement (which we all agree is tough enough!), I often think about the viewer's experience. When people see these 'correct' images on their own computer, I won't know exactly what they see because each computer's color settings and the viewing conditions can be so different. I'm not sure what if anything can be done towards this end, but it's often in the back of my mind and I'd love to hear some ideas.

Many thanks Yair,

 

this is very helpful.

 

Regards,

 

David Rowan.

 

http://www.davidrowan.org

http://grand-union.org.uk

 

 

 

 

 

 

 

 

 

 

 

On 11 January 2018, at 02:21 pm, Yair Shahar <[log in to unmask]> wrote:

Hello David,

 

Adobe’s .dcp file format can only be (officially) used in Photoshop, Lightroom and the Adobe DNG Profile Editor. If you want to create custom Input profiles for your camera and your workflow is based on Capture One, you will need to either:

 

1. Use a software such as BasicColor that generates profiles in .icc format
2. Use an existing Input Profile, edit it in Capture One (with the Color Editor) and save it as a new icc profile. This is more popular for product photography where a specific tone (e.g. Coca Cola Red) need to be recorded accurately.

 

Capture One supports .icc and .icm profile file formats. The Colormunki creates .icc files. You need to make sure that the profiles are stored correctly so that the operating system and applications such as Capture One can pick them up (see https://www.xrite.com/service-support/icc_profile_locations_on_mac_and_pc_operating_systems )

 

By default, Capture One will assign the Output profile which you have selected in your recipe (e.g. Adobe RGB, sRGB or any other RGB/ CMYK profile) and will display the colour values based on that profile.

 

If you create a custom display profile and you wish to see its values there are two ways for doing that:

 

1. Select it in your recipe
2. Select it as a Proof profile (Menu>View>Proof Profile

 

If you create a profile for your printer, you can do the same, so you process your images with your custom profile embedded and soft proof the same profile.

 

This is true for any version of Capture One.

 

Hope this helps (and I’ve only used the word profile a dozen times or so)

 

BR

 

Yair

 

 

Yair Shahar | Product Manager | Phase One

[log in to unmask] | +44 77 8992 8199

 

 

 

 

 

From: AHFAP UK cultural heritage sector <[log in to unmask]> on behalf of David Rowan <[log in to unmask]>
Reply-To: AHFAP UK cultural heritage sector <[log in to unmask]>
Date: Thursday, 11 January 2018 at 11:29
To: AHFAP UK cultural heritage sector <[log in to unmask]>
Subject: Accurate colour reproduction

 

Hello Yair and Clare.

 

Quick question for Yair:

 

I'm working with a capture one pro/DB workflow, have the x-rite iDisplay Pro /SG CC and more recently the bought the colourmunki pro profile tool.

 

I found with the colourmunki I couldn't create a custom profile in a format that Capture One Pro could use or would need to employ a complex set of command line codes to convert the .dcp files ..

 

Is this potentially an issue thats solved with the Cultural Heritage version ?

 

I'm following this discussion with interest, would also be interested in attending an AHFAP talk on the subject.

 

Thanks

 

 

David Rowan.

http://www.davidrowan.org

 

 

 

 

 

 

 

 

 

 

 

 

 

On 09 January 2018, at 12:33 pm, Yair Shahar <[log in to unmask]> wrote:

 

For those interested in this subject and who use Capture One there’s a Colour Reproduction Guide on our CH page:

 

http://bit.ly/2CWm2iM

 

As Andrew suggests not all SG charts are created equal! It is also essential to make sure the angle of the lights is adjusted so there are no reflections from its semi-matt surface, especially the Black patches as they will record higher L* values.

 

Hope this helps

 

Yair

 

 

Yair Shahar | Product Manager | Phase One

[log in to unmask] | +44 77 8992 8199

 

 

From: AHFAP UK cultural heritage sector <[log in to unmask]> on behalf of "Hunter, Elizabeth" <[log in to unmask]>
Reply-To: AHFAP UK cultural heritage sector <[log in to unmask]>
Date: Tuesday, 9 January 2018 at 11:46
To: AHFAP UK cultural heritage sector <[log in to unmask]>
Subject: Re: Accurate colour reproduction

 

Hi Andrew,

Good response!

This subject always crops up.

I wonder if we should have an AHFAP colour management workshop, and pool our ideas. 

It could be helpful for people to get a broader understanding of the subject as a whole, to help make decisions for their own best practice.

Everyone has different equipment, and lighting environments, especially photographers having to operate in less than ideal conditions.

It was a subject much talked about in the Rijksmuseum conference a couple of years ago, where they favour Metamorfoze.

Elizabeth.

 

 

 

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Elizabeth Hunter Senior Imaging Technician British Library    T +44(0) 20 7421 7000 (extn. 7972) [log in to unmask]

The British Library 96 Euston Road London NW1 2DB www.bl.uk

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From: UK AHFAP <[log in to unmask]> on behalf of Andrew Bruce <[log in to unmask]>
Reply-To: UK AHFAP <[log in to unmask]>
Date: Tuesday, 9 January 2018 at 11:28
To: UK AHFAP <[log in to unmask]>
Subject: Re: Accurate colour reproduction

 

Hi Claire

My favourite subject!  - the can of worms has been opened

Firstly, when comparing your monitor to the actual original artwork, unless your artwork is located under the non-real-world ideal conditions of a quality viewing booth with D50 illumination, your monitor has enough gamut to represent the colours of the artwork, monitor brightness has been adjusted to match the booths brightness and your monitor is also set to D50 white point rather than the more common D65) then there will always be a discrepancy. Even with all of these ideal conditions set perfectly, then there will still probably be discrepancies because our eyes simply aren't good at this kind of thing. This is why the non-subjective approaches of metamorfoze/fadgi/iso19264 are so valuable.

As we don't use Haselblad's and Phocus here at the Postal Museum i'm far from the best person to advice on that. However my understanding is that in Phocus either you can apply a custom ICC profile to chaicterize the sensor (built in external software such as BasICColor) that is detailed here: http://www.sfoto.se/sites/default/files/article_attachments/imagingetc_hasselblad.pdf
or rather than creating an ICC profile then Phocus can charicterize (or as they call it 'calibrate') the sensor, as detailed here: http://static.hasselblad.com/2014/12/Phocus-2.9.1-Mac-read-me.pdf

We're so used to seeing images that have had a contrast curve added for aesthetic reasons, or have boosted contrast due to the gamma curve in the images colour profile that when we then start to look at proper art reproduction images they can indeed look visually very flat and desaturated. This is just something to be conscious of.

Ideally you want to measure your own Colorchecker SG chart with a spectrophotometer, so you know what the exact L* values are for YOUR chart - my E5 patch for example is about 1 L* brighter than the measurements x-rite publish. And these measurements can also be used to produce a much more precise charicterization of the sensor. It's also good to know which is the most spectrally neutral patch to set white balance from.
But yes - setting your white balance using patch G5, then adjusting the camera exposure until patch E5 is reading L*96.5 (246G in eciRGBv2) is just the ticket.
It's also worth noting that when you're characterizing your camera, rather than using general-use or art-repro canned profiles, then the accuracy of everything needs to greatly increase - lights need to be precisely 45', ambient light needs to be at a minimum, white walls and ceilings that reflect need to be controlled.
In this kind of workflow you shouldn't have to do any colour correction (beyond setting the exposure, setting the white point and making sure the right tone curve and profile are selected) as that's the point of this kind of workflow - it takes the inherent flaws of the human visual system out of the equation. You can obviously go on to make derivative files with adjustments to the contrast and colour, but the master file should stay untouched.

Hope that helps

Best Wishes
Andrew

 

 

Andrew Bruce

Digitisation Officer

The Postal Museum | 15-20 Phoenix Place | London WC1X 0DA

T: +44 (0)300 0300 700 | M: 07766 620308 | E: [log in to unmask]

The Postal Museum is the public identity of the Postal Heritage Trust. Registered as a charity in England and Wales. Registered Charity Number 1102360. Company Number 48960

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From: AHFAP, for image professionals in the UK cultural heritage sector <[log in to unmask]> on behalf of Claire Collins <[log in to unmask]>
Sent: 09 January 2018 10:38:34
To: [log in to unmask]
Subject: Accurate colour reproduction

 

 

Hi Everyone,

 

I’m looking for some advice on colour calibration and adjustment of colour (eek, that dreaded subject!). I am using a Hasselblad H4D 50, with an 80mm lens on a Kaiser light table. The constant bulbs are daylight balanced. I have persuaded the organisation that I am working for to invest in a lovely new Colourchecker digital SG card and am using Phocus software. I have an Eizo Coloredge CG211 screen which I calibrate using an i1 Display Pro. ‘Reproduction’ is ticked in Phocus and I have used the SG card with the calibration function to set the ‘colour calibration’ and I have the working space set on Hasselblad L*RGB, which is recommended in the Phocus guidelines for reproducing artworks.

I set the camera to the correct position to mostly fill the frame with the artwork. I then take a picture of the SG card. I then use the dropper to pick the white balance on a neutral grey square (generally G5). I then check the values of E5, H5, J5, making sure they are around the values 245, 120, 40 (I have read varying opinions on these numbers, but this is where I’m at for now). I then take a picture of my first bit of artwork. Hmmm, it doesn’t look quite right, all the colours are wishy washy.

 

So this is the question. Have I got something set wrong? Do I adjust by eye until it looks correct? If I play with the colour correction wheel in Phocus I can get the colour card to look on screen as it does to my eye, but does this defeat the point of the colour balance tool and the reproduction mode? Is it supposed to look far more de-saturated than the original artwork? Do I trust that my screen is correct (I have calibrated it but how do I know that it worked correctly?). Are there exact colour values for the other colours on the card that I can check against or am I in fact missing the point of the colour card?  I’ve tried printing some images and the colour is coming out very muted (the printer is not however calibrated, as far as I know).

 

Any advice would be much appreciated, thanks.

 

 

 

 

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