Joseph,

that’s not quite accurate.

Aperture should not be clipping values during export. This is why we have Colorsync. It will ‘re-map’ them into the chosen colour space using what we hope, is the best ‘intent’ for the purpose. We can’t choose the intent for export in Aperture, unlike PS or even the MacOS.

So … if for example an image is in AdobeRGB and contains colours which lie outside of sRGB, when you choose to export using sRGB, those colours, lying outside sRGB will be ‘mapped’ to new colours which lie inside sRGB. The result of this will be a loss of saturation, because it is the saturated colours which AdobeRGB can contain, that are outside sRGB’s gamut. However … there should be no ‘clipping’. Nothing is getting ‘chopped off’. Instead the file is being altered in the best way possible, to retain the visual perception of the original AdobeRGB file, but in the smaller sRGB space (perceptual intent).

This though does not preclude banding issues appearing, although most commonly banding that shows up in an 8-bit file may well have been present in the 16-bit version, but imperceptibly. The transition to 8-bit will exaggerate the effect and it will become a problem. That said … banding is not a major issue these days. It used to be though.

So the ideal thing to do if you want to work in 8-bit, is to do any big tonal adjustments inside 16-bit and then export to 8-bit and do the rest of the work on the file.

(I will re-iterate though, that you can do anything that Silver Effects can do, in Aperture itself.)

Even though you’re in black and white, it’s still a question of the number of ‘steps’ that you have in your file. If you are doing any kind of big curve adjustments (tonal) then 16 will make a big difference and avoid any banding.

To ensure … yes.

It’s a difficult call, because 8-bits covers everything that human beings can distinguish and often 8-bits will be plenty to cover your adjustments and keep transitions smooth … but what if it isn’t ? You can either spend time scrutinising your finished files, to ensure that all is good … or just use 16-bit and not have to worry. Actually … you can push 16-bits too far as well, with extreme adjustments, but these are well outside normal usage … but it does bring back the same question … is 16 enough ?  :) :)

Hell, what do I know Joseph.  ;) ;) I’ve been working in 16-bits all the way back to 1997 in LP. 8-bits out, but all 16-bits right up until the last push of the button for build (export).

PS used to get very ugly back in those days in 8-bit. Simply the act of opening a file in PS reduced it to 7-bits. A single sharpening would bring it down to 6-bits and a curve adjustment on top would reduce it to 5-bits. Yuk. These days PS only applies edits at the end, when you flatten the file, which really copied the LP approach and significantly limits the damage. Aperture is much like LP in that all internal operations are in 16-bit and your edits are all applied at the end, when you export, so it gives you the cleanest file possible.

I guess to answer ‘stump’ … knowing that silver effects pro give you nothing that you can’t do in Aperture alone, the answer would be to learn how to use Aperture more throughly, and enjoy not having to export a 16-bit tiff ? It’s all just tonal adjustments. Curves will do pretty much everything … but I have to admit, that the new Highlights and Shadows brick makes a lot, very easy.

Joseph,

clipping is very bad and no body wants it, so software engineers go out of there way to avoid it. It’s like your glass analogy or perhaps like using scissors to cut around an image. Bad news.

Re-mapping, will either:

a) Squeeze colours into the smaller gamut. Think ; digital ‘cyan’ skies a few years ago. These were due to clipping. Usually when photographing a blue sky, the red the channel hits 255 first, leaving the other 2 alone to provide colour information. As those 2 remaining channels increase in exposure towards 255, they increase their influence in the relationship between the 3 channels, over the rendered colour. Eventually, one of the other 2 remaining channels will top-out at 255 and the colour will once again, veer towards the remaining colour (usually green) and so you will again see a weird transition, until finally the 3rd channel will also top-out at 255 and you will just have white (255/255/255).

The red, then blue channels were ‘clipped’ so the colour was inaccurate. Eventually manufacturers and software engineers learned to make this transition to white 255/255/255 more gracefully and so nowadays software re-maps at the white end, to simulate the way that film would blow highlights.

b) Re-map more literally into a smaller space (or larger space!!) so that the perception of the image/colours is as close as possible, but using subtly different colours. This can be done either 1) perceptually, so that the colours ‘look’ as similar as possible to the original, or 2) relatively, so that the relationship (their physical position inside the colour space) remains the same.

For your raw example :

The software (Aperture) is giving you complete control and so is allowing you the choice concerning the blown highlights to either a) leave them ‘clipped’ (see above) or b) manage the extent of the remapping yourself. But NB, this is not ‘recovering’ anything, because there is nothing there to be recovered. Instead, it is using detail information available in the remaining 1 or 2 channels to ‘create’ information for the clipped ‘missing’ channel. I’m not sure precisely how this is done, perhaps it varies between softwares, but I would guess that it looks at surrounding pixels for blown highlights (those at 255), then looks for that channel’s surrounding pixels which are still at 254 or 253 and then compares the relationship of those 254/253 pixels to the other 1 or 2 channels. It then knows what colour it should be. Now it can squeeze all 3 channels together (remapping) towards a 254 max, but using the colour relationship that it now understands and thus giving the correct colour (for the scene) and … it will avoid banding(!) and … will have as natural a look as possible.

That’s no small feat and as you will have noticed, the more colour information that you have lost, the harder it is for the software to ‘create’ it.

Hi,

I like to add the following question to this discussion.

When making sure there is no clipping before exporting the image as an 8-bit TIFF, does this limit the external software in color usage because the TIFF container is 8-bit? In other words, is it possible for the external software to generate (color) banding because of the 8-bit TIFF container?

With kind regards, Dennis