Highlight Hot Areas Threshold Preference

by Ben Long

Aperture's Highlight Hot Areas command (which you can access from the View menu, or by pressing Option-Shift-H) activates a highlight clipping display in the Viewer pane. This display shows any pixels that have clipped highlights. You activate this feature by choosing View > Highlight Hot Areas, or by pressing Option-Shift-H. Aperture will display any clipped pixels as red.

highlightHotAreas.png

With clipped highlights displayed you can then use Levels or the Exposure Slider or the Brightness slider to darken your image until the clipped areas are gone.

However, if you've used the tool much, you may have noticed that it will sometimes indicate that there are no clipped pixels, even though a tiny spike remains on the right side of the histogram. This behavior is not a bug, it's actually by design. If you look in Aperture's preferences, you'll see a slider labelled Hot Area Display Threshold. This controls what actually "counts" as a clipped highlight for the Hot Area Display. By default, this slider is set to 94%. You can't set it to 100, but you can move it up to 99% if you want a Hot Area Display that corresponds more closely to the clipping that you'll see in the Histogram.

hotAreaSliderPref.png

The idea behind this control is that not all printers have the same white point. Some actually max out before the white that is displayed on your monitor. So, Aperture allows you to change the clipping display threshold to more accurately reflect the white point of printed output. For most instances, the default behavior will be all that you need, but if you want to make extremely refined adjustments to the very brightest highlights in your image, then you might want to change this parameter to a higher value.

6 Comments

David Medina
2007-07-06 16:47:12
This a most welcome subject. I been looking everywhere for this answer to no avail. Thanks! Could you do a follow up on how to ptoperly deal with highlight recovery? That would be awesome.
Charles Maclauchlan
2007-07-06 22:22:20
I wonder if the hotpoint adjustment could be part of the printing problem I'm experiencing. I have begun using an HP B9180, mostly for B&W. I notice prints from Aperture are much darker than from CS3 or from Qimage. Interestingly though Aperture does seem to print color to my DJ130 correctly, so...???
tbwiv
2007-07-11 08:22:28
For David:


This is my biggest gripe with dSLRs -- the sensors are very limited in dynamic range compared to film. They don't seem to do well with the highlights, although the shadows are usually recoverable. So my solution is to underexpose when I shoot and use the shadow slider to recover detail in the dark areas. If you still have hot spots in post-processing, use the exposure slider (assuming you shoot RAW) to achieve the underexposure -- just slide it left enough to get rid of the highlights. It's virtually the same as underexposing when you shoot, but you'll be adding a little noise.


The amount to underexpose is the tricky part. When you're on location, shoot a few trial shots and review the shots using your camera's highlight feature. Underexpose just enough to eliminate the hot spots. Hopefully the next generation of sensors will have a wider dynamic range!


Full disclosure: I'm an amateur with very little formal training. Good luck!


2007-07-12 16:18:44
"not all printers have the same white point. Some actually max out before the white that is displayed on your monitor"
Assuming I have the printer's profile, how can I find that information. (softproof with the printer profile?)
jim N.
2007-07-14 10:51:09
any idea why hotpoints are different in Aperture, ACR, andPs? If I use curves in Ps and ensure that no highlights are blown, I'll regularly see blown highlights in the same image in Aperture. Which program is correct?
Jenn
2007-07-19 19:23:43
Wow. I just tried this and am amazed. I didn't know editing highlights was possible. My clouds were one white blob in the sky, but now they match their reflection, and even have a little gray. I thought the whole picture might be a lot darker, but it looks good. Thanks so much for this tip.