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Articoli tecnici

Questo articolo non disponibile in Italiano
July 2008

Jonathan Briggs

The more work that can be done on image files in a non-destructive processing environment, the better. It‘s all about getting the 'best value' out of the information provided by the camera, and effectively using the unlimited potential for re-interpreting image data. The continued development of Aperture software by Apple culminated earlier in 2008 in the arrival of version 2.1 and this release brings a significant number of new tools and working practices into the realm of non-destructive workflow.

Non-destructive processing is when a piece of software simply applies commands to the data that forms an image file. Pixels don‘t get altered, and the original files never get over-saved. Such an approach saves disk space and avoids reliance on history states. Come back to an image next week or next year and you'll still have the original (known as the ‘Master File’) sitting quietly in the background, plus all the adjustments you've made remaining at your command. This is exactly how Aperture works.

However, what‘s exciting about the latest incarnation is that tools and techniques are coming forward into Aperture that have previously been the domain of pixel-based editing software - the best known of which is Adobe Photoshop. Retouching and cloning are two good examples but, as is demonstrated below, the list now even extends to Dodge & Burn retouching techniques.

© Sara France

The Histogram in Luminance mode doesn’t express this as an overexposed image, despite it obviously being so.

The most effective way of explaining the real potential that Aperture offers is by way of example. By walking through the image adjustment commands made on a particularly demanding wedding image, we‘ll see in detail how an image can be reinterpreted and essentially ‘recaptured’. This gets around the trials and tribulations of the moment and enables a properly balanced and detailed image to be the final result.

To start the ball rolling, let‘s look at the master image file - the picture straight off the camera. Clearly this wedding image is overexposed, yet the Histogram in overall Luminance mode doesn‘t appear to suggest that the highlights are clipped.

This is a good example of when the Luminance graph fails to tell the whole story. A click of the Action button above the Histogram provides options to view as RGB or channel by channel. The RGB version tells the true tale of this image, with the Blue channel clipping significantly in the Highlights.


©Sara France

Use the action button (cog) to gain access to the Histogram options. In RGB mode the blue channel can be seen clipping in the highlights of the image.

To correct this problem, the Exposure and Recovery controls should be used in tandem. The Exposure control will always shift all the data in an image, whilst Recovery just concentrates on the top end or highlights. Move the sliders to see the differing effects. In this instance, Exposure can be reduced just a touch, and Recovery utilised to the max, in order to bring all the data into range, but without pulling back the whole feel of the picture. It‘s the dress we‘re particularly concerned about here, but it‘s essential to maintain the look of the skin tones too.

© Sara France

Use Exposure and Recovery together to recapture the blown out highlights without interfering too much with the overall feel of the image.

Next into the mix comes the Black Point. The background shadow of the room behind our subject is by no means the focus of this picture, so the Black Point can be touched over a little. Again, reference the Histogram to check for any major clipping of shadows in the hair, and use the Zoom control (Z key) to go right in and check out what‘s happening on the spot.

© Sara France

Thankfully, digital photography still relies on us humans to think about the pros and cons of a picture. Here, some of the dark areas in the hair can be allowed to clip (shown by the blue dots), since that’s fine considering the context of the shot.

Inside Aperture 2 (Pt. 3)

Moving on now to the Enhance section of the Adjustments Inspector finds tools for Saturation and Vibrancy. Similar to the difference between Exposure and Recovery, Vibrancy only acts on specific colour ranges in an image. Whilst Saturation is a broad-brush tool, Vibrancy will generally leave skin tones alone as far as possible. It‘s a much more subtle approach. However, adding Saturation is — generally speaking — a necessity with many a RAW file. The trick is to be gentle on your application.

Naturally, there will be differences between different camera models, but just a dab to the right on the slider is enough - a value of 1.1 will do. Many demos will talk about bumping up the inimitable blue sky, but let‘s be realistic: the intention is to refine, and that means keeping everything believable. With the extra touch of Saturation coming first, Vibrancy can be set to good effect. The same rules apply here — try to keep it as realistic as possible.

Remember that use of the Saturation and Vibrancy controls will have also affected the Histogram, so now is a good time to click on the Levels tick box and use the channel drop-down list to view each colour channel separately and check for clipping at either end of the Histogram. Note that clipping is not out of the question. The point is to be aware of what is happening, and also where in the image. If in doubt, select the Highlight Hot & Cold Areas option from the View menu and adjust as necessary. It may be in this example that you‘d let a little shadow detail go in the hair in return for a better overall feel of the picture. Life is, as ever, a compromise.

© Sara France

Adjustments have been made to correct the overall exposure and set the saturation and vibrancy for the skin. This throws up another set of problems with the dress, which can be handled next.

Whilst our Histogram is now showing an orderly graph, here we have a dress that‘s covered in detail, yet we can‘t see it properly. This is where reinterpreting a file can be most powerful. Using Aperture‘s Highlights & Shadows tool it‘s possible to control the glare of the white fabric and show the detail that‘s in the image but is, as yet, hidden. Drag over the Highlights slider and watch how the top end of the Histogram changes, with highlights pushing back towards the mid-tones. Close examination reveals a wealth of detail that was formerly unseen.

© Sara France

Use the Highlights slider to rework the detail viewable in the dress fabric, and control glare.

This is all well and good, but there’s still much work to be done. Our commands so far have taken us in the right direction but have also revealed colour elements that are distinctly undesirable. It can now be seen just how much blue is making up the dress, and the skin tones need a tweak to boot. Hence it is necessary to isolate various colour ranges in this image and control them separately. Expand the Colour palette and switch to the Expanded View Mode for ease of use. Notice that each part has an eyedropper within its representative colour swatch. This indicates that it can be programmed.

To neutralise the tones of the dress, those blues need isolating, so click the eyedropper in the first swatch and sample a suitable area of the dress where the blues are strongest. Now slide back the ‘S’ slider (for Saturation) all the way to left, and the dress becomes more neutral. The ‘L’ slider can be tweaked back a little to taste, depending on how bright you want the dress to appear, as you’re reducing the white element of this colour range.

Now we head down to the next Swatch and follow the same routine, this time sampling from the curtain and knocking back the Saturation about a third and a little less Luminance too. This is repeated on the third Swatch, sampling the skin tones of her upper arm and increasing the Luminance to help her skin shine. A logical extension of the process can be to then sample the reds of her lips and give that a bit more punch too. This will also warm the skin tone a little, which is no bad thing in this instance.

Just a tweak in the reds to Saturation and Luminance radically improves the viewer’s perception of her skin and also body shape. Once more, a little touch makes a whole lot of difference. Now zoom in to the area around her lower arm and continue to refine the shadow areas of the dress by sampling another blue shade and as strong a magenta tone as possible until a clean result is achieved.

© Sara France

The programmable colour palette is hugely powerful, effectively bringing selective adjustments to the Aperture user.

It’s also worth being aware of the new facility to set which parts of the Adjustments Inspector are shown by default. The Action button found in each section allows the user to Add or Remove that palette from the default set, which is handy when you are working regularly on similar types of images, and hence need the same tool set available.

© Sara France

Decide which palettes appear in the Adjustments Inspector by default by making a selection from the Action button.

The next challenge is to clean up our subject’s skin. There is no understating the extent to which a decent brush up of spots, bumps and skin imperfections can enhance the feel of an image. Previously reserved for pixel-based programs, all the functionality is now within Aperture 2.1 to enable retouching, cloning and even Dodge & Burn actions. Let’s begin with effective use of the Retouch tool. Click the Brush icon at the base of the Aperture screen and you’re faced with a display offering Repair or Clone options. For any work to remove skin imperfections the knack is to keep the radius a touch bigger than the area you’re correcting.

Inside Aperture 2 (Pt. 3)

So first off, zoom the viewer to 100% and navigate using either the space bar and hand, or the navigator square, to the relevant point in the image. Set the required radius - in this instance 15 is generally about right for most of our actions, but do be prepared to be constantly changing the radius as you move. The Softness should be set about half way across its slider, so set the value to 0.5. This means that the outer half of the brush diameter will be feathered, so merging the brush stroke effectively with the surrounding skin. This can be improved still further by dropping the opacity to around 0.85. Leave the source on Automatic and Detect edges clicked too. Now go around the image making single clicks of the brush — don’t be tempted to drag around — and the Retouch tool will make perfect corrections around her face and upper body.

© Sara France

There isn’t a face in existence that won’t benefit from a gentle touch up and clean round. Use the Retouch brush in Repair and Clone modes to achieve an effective result.

If you find a couple of spots that need correcting but are too close together for the Repair tool to make a decent job of it, change to the Clone variety and take a sample point using the Option key about a brush width's away from the point in need of correction, and you'll find success. Work around her face and upper body in this manner, not forgetting her hand too, which has a few points in need of attention! Back over in the Adjustments Inspector you can now find the Retouch section with a count of how many strokes have been made. It's possible to step back by deleting each move made, or the whole lot can go using the Reset key.

With a little practice, the Retouch tool becomes invaluable — pretty impressive in a non-destructive environment. Zoom the viewer back so the whole image can be seen to check the overall view of the work. Now press the M key to see the Master File (i.e. before all the hard work!) and enjoy the difference that's been made here. Once achieved, this really does enforce the notion that capture on camera is only the beginning of the process of photography — and still, at any time, any or all of the adjustments may be re-tweaked or removed at will, with the original sitting safe and sound in the background. One file powers all.

Cropping an image is another area of workflow that works far better non-destructively — simply because you’re not actually losing any of the image, just changing how it’s seen. In Aperture 2.1 this facility has been improved by the addition of a variety of options as to how a crop is made. Particularly useful is the Master Aspect Ratio, which makes it really easy to enact a crop whilst keeping the original proportions intact. You just drag across the image to command the crop, and then press Return. Just press the C key to readjust at any time.

© Sara France

Entering the Dodge & Burn overlay gives access to a range of tools to perform the final touches to an image.

To finish off our work on this image, it would be great to be able to address one or two details that would make all the difference to the image. There’s a shadow on the left-hand side of her face that could do with lightening, and the creases down the front of dress would benefit from fading off. This takes us to a really clever new side of Aperture 2.1. Built into the program is a new section that can be found under the Images menu.

Select the Edit with item, and then Dodge & Burn. This is the only time that Aperture takes your Master, plus adjustments so far, to make a new rendered file. This will appear as a new thumbnail next to your original and is indicated by a circular icon. We’ve now left the non-destructive world and entered a pixel-based overlay to Aperture offering an array of Dodge & Burn and similar tools.

© Sara France

We’ve come a long way from the original shot file… all achieved in Aperture 2.1

Again, use the slider at the bottom left of the new viewer to zoom in on the file, or just press Z, and set a suitable brush size — make it really soft and experiment with the strength. For example, use the Dodge brush to lighten the shadow we talked about and to fade off the horizontal creases across the waist. The effect of these moves can be startling, and really make a fine job of the image. There's so much power here, it’s necessary to play around. But note: when you're done and Save is pressed, there's no going back — these changes are applied to the new rendered file created in Aperture. You can go again and do more, but once you save a session that's it. Of course, you can always delete this second file and start this side of the process again by rendering out your finished RAW version once more.

It can’t be stressed enough, though, just how this functionality takes Aperture to a whole new level. Portrait and Fashion work can now be produced from start to finish within Aperture. Add to that the release of the developer code to the wide world, and the range of ‘Edit with’ plug in environments for Aperture 2.1 and beyond will most likely explode. The pace of change and development in digital photography as whole is lightning quick, and Aperture seems to be glued to the fast track.