Black Point Compensation (BPC) applied twice to an image = shadow or colour issues?

[Hmmokthen]

Hi, Ive had conflicting advice from Adobe agents and I was hoping someone could confirm what happens in this situation: if Black Point Compensation (BPC) is applied twice to an image you could have shadow or colour issues?

Circumstances could be: export image from LR into a jpg (which applies BPC) and then you send it off to a professional print service who then use BPC in their print software.

Another example could be: Doing a colour conversion in PS (which applies BPC) and then you print with "PS manages colors" and "BPC" enabled. Note: soft-proofing can give BPC but it is only temporary for the preview, not baked into the image file, I believe.

Thanks

[Stephen Marsh]

In almost all situations, you would want to enable BPC when using Relative Colorimetric rendering intent, especially when going from an RGB working/editing space to a printer profile. If using non-Adobe software that doesn't offer BPC, I would then use Perceptual rendering over Relative Colorimetric if there was any concern of losing shadow detail. In some very rare non-photographic situations which are very image specific, one may prefer to go from CMYK to RGB using Relative Colorimetric without BPC, however, this would be very rare. BPC generally helps more than it hurts, which is why it's there.

[Hmmokthen]

thanks for the reply. So, you've never had any shadow or color issues when BPC has been applied twice in your workflow?

[D Fosse]

BPC can't be "applied twice". It rolls off any clipping if the black point is higher in the destination. If there isn't clipping, it doesn't do anything.

Again, are you seeing any specific problems?

[Hmmokthen]

no im not seeing probems. Im just confused why an adobe agent said it could be applie twice and cause shadow + colour issues

[D Fosse]

Well, that's not correct.

[NB, colourmanagement]

@Hmmokthen " Im just confused why an adobe agent said it could be applie twice and cause shadow + colour issues"

I too think they were wrong, either they made a mistake or don't understand what BPC does.

I hope this helps

neil barstow colourmanagement - adobe forum volunteer,

colourmanagement consultant & co-author of 'getting colour right'

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[D Fosse]

Right. BPC should in practice always be on.

Do you experience black clipping, or lifted blacks, somewhere? Then there are other reasons for it.

[davescm]

Black point compensation is designed to avoid clipping of near black values. In your example of moving from a large document space to a smaller document space, then to an even smaller print space, leaving black compensation off at either conversion will result in near black values being clipped and, once clipped, they cannot be recovered in a later conversion. 

Dave