replacing the blue sky

Yesterday I spent some time attempting to get an interesting shot of the light through the avenue of trees at Badbury Rings just north of Poole in the UK.

There was a deep blue sky but by the time I'd raised the brightness of the shaded areas in post processing, the sky is now a bright white. Anyone know if I can reintroduce a blue sky (I can easily create a layer in Photoshop CS2 of the actual colour) to replace the nasty white?

I feel it should be straightforward, but whatever I try seems to fall short. The snag is that the sky is not a single area, its intermixed among the leaves, branches, grass etc.

What about mixing a version of the shot with the blue still there with my preferred version with more light in the shadows? Sort of HDR thinking?

Lowner wrote in post #16124367
Sort of HDR thinking?

That is one of the reasons why HDR is needed - our cameras just falls short of matching our eyes.

I presume you shot Raw. Do two conversions from DPP, one opened shadows and one blue sky, and do a HDR blend. A variation you might like to try is to do a linear conversion for the blue sky version.

Does CS2 have a "replace color" tool? You could try darkening the sky back down with that.

My grateful thanks for your responses.

In answer to ScubaDude I don't know is the honest reply. I'm very new to it having recently "upgraded" from PS7.

And Elie: Yes, they are RAW, but I'm a complete greenhorn so you will need to explain how I merge the two "before and after" versions together. It is what I had hoped I could do.

I've attached a sample to show the problem.

Here's a typical example of how the sky looked before I started fiddling to lighten the shade!

I think that the easiest way for you would be to use one of the specialized HDR programs. Photomatix is the market leader, but I use Dynamic-Photo HDR occasionally. I don't use it very often, however, because (if you will forgive my not being able to resist saying "I told you so,") an image like the one above is well within the DR rendered by Lightroom. Here is a recent image in similar lighting (shot in North Ireland).

Elie,

You are in the perfect place to say "I told you so" and I accept the rebuke but as you know I am so anti LR nothing on earth will ever persuade me to use it.

So you cannot suggest a method of doing this merging of different versions in CS2?

Unfortunately, I think "Merge to HDR" was added to a later version. It would still be possible to do in PSCS2, but with a lot of laborious masking. That's why I suggested those other programs, both of which, I believe, have free trials. There are also several other HDR programs, including the Open Source (free) Enfuse which is highly thought of.

You might try a trial version of one of the dedicated HDR programs. The only one I have experience with is NIK HDR Efex Pro, so that is the only one I can speak to. The NIK program can work with a single RAW file and sometimes does an amazing job of recovering highlights and shadows without first creating two or more exposures in Lightroom. Although normally thought of as a plug-in, HDR Efex Pro can also run as a stand-alone program.

Why not upload a RAW file somewhere and let someone give it a test for you?

EDIT -- One more thought, Refine Edge in the later versions of Photoshop or Elements might be able to handle the selection task so that you can do a sky replacement, if someone wanted to give that a try.

Richard,
There are also other Raw converters that you can try and they may give you better DR than DPP. Capture One from Phase One is Adobe's primary competitor among Windows users and is excellent, but it also utilizes a database, so you may not like it. But Silky Pix and Raw Therapee (donationware) would certainly be worthwhile trying.

Where you have trees or hair in the image... http://av.adobe.com/ru​ssellbrown/ExtractSM.m​ov

The Essential Approach to Masking in Photoshop

RIchard - If your original image captured the sky "correctly" and it was not blown out, this would likely mean that your trees appear dark and underexposed. The "ideal" exposure would be one in which you overexposed the sky by about 1 stop in camera and then pulled the exposure back 1 stop in raw conversion (ETTR) to get well exposed sky with shadows that are relatively noise free.

In any event, as long as the shadows are not ruined with noise, it sounds like all you need to do is convert the image from raw with an exposure that gets the sky tonal range correct. Then, in Photoshop, simply bring up the trees, etc. in the 3/4 tones and shadows by doing the following:

1) duplicate the background onto a new layer (CMD-J, CTRL-J on a PC)
2) make a new, blank layer mask for this layer
3) Set the blend mode of this new layer to "Screen"
4) with the layer mask selected, go it the menu item "Image > Apply Image"
Select:
Layer: background image
Channel: Blue
{Check the "invert" checkbox)

This operation will put an inverted copy of the image's blue channel in the layer mask. WHy would you want to do this? Because the "screen" operation will naturally open up shadows, but you want to restrict the effect to everything but the sky. The Blue channel of the original will be light in the sky areas, which have a lot of blue, especially compared to the trees. So, this is a great natural mask for precisely this operation! You want in inverted blue channel so that the sky becomes dark in the mask, protecting the sky from the screen operation.

As an extra bonus, if you need to darken the sky while leaving everything else untouched, duplicate the Screen layer, but set its blend mode to "Multiply" - then INVERT the mask so that the sky areas are white (i.e., the original blue channel). Multiply will darken tones and the mask will target the sky and leave everything else alone.

You can use the Opacity of each layer to season the effect to taste. The idea here is that you have a mask built right into the scene to do what you want to do. If you choose to make two separate conversions from the raw file, one for the sky and one for everything else, you can still use this approach to blend the two without having to mask by hand.

Sometimes this kind of operation makes for an unnatural appearance of the relative tonality of the sky and the lifted shadow areas - the lifted shadow areas are too light and the contrast between these areas and the scene just doesn't appear natural. To tone this down while still retaining the targeted adjustment, you can use the Blend If sliders on your screen layer to allow some of the original, darker shadow tones back through.

To do this, double click on the right area of the screen layer in the layers panel to bring up the layer styles window - in the "underlying layer" blend if slider area you want to hold down the option (alt on a PC) key and click and drag the black point marker to separate the two halves. Drag the right half from 0 all the way to 255 (the white point end). This will blend the original shadows partially back into the new lightened shadows and make a more convincing blend.

kirk

If you can upload one of the raw files, we can take a whack at it.

Kirk

Here is an example - I shot this image for test reasons having nothing to do with this exercise, but it works to demonstrate the concept in this thread. ISO 100, f/5.6, 1/320. The sky, by default in Aperture, appears partially blown. By reducing the exposure by 2EV, I have a perfectly serviceable sky. In images like this, where there is a lot of blue sky ambient fill light, there is rarely a need for HDR techniques. ETTR will get you most of the way there, most of the time.

The first attached image is the raw conversion, opened in PS.

The second attached image shows the result after applying two screen layer passes (Extreme! I made one at 100% opacity and I just duplicated the screen layer and got more boost, a little too much here - the contrast is unnatural, as I described previously - but enough to demonstrate the point). Because you are compressing the tonal range with this operation, you will likely need to reestablish some contrast, global and local. After you do that, you will likely need to add some color boost back into the mix. The second attached image has these two operations applied as well.

In the next post I will attach the mask derived from the original blue channel. I curved the blue channel to add contrast to the mask.

kirk