Temple Bridge Taroko Gorge

This is the forum for posting to the June 2010 CM 101 Class
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Postby imported_BoydMac » Sun Jul 25, 2010 3:59 am

Well, I've finally caught up just as the course ends.  I apologize for not having participated in the exchanges.  Nevertheless, I've learned a great deal and am anxious to start using this knowledge and the backlog of photo's I have waiting to be processed.  I've particularly enjoyed weeks five and six.  I must admit, I found the Temple Bridge to be particularly challenging.  If the bridge color cast was corrected first, I found that I was limited in what I could do to the greens.  I could get increased separation, but not the saturation I desired.  If I waited until after adjusting the folage, much of the green saturation was lost when the bridge was corrected.  Finally I just used a mask to limit the bridge's color correction to the brighter objects. 
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Postby leeharper_admin » Sun Jul 25, 2010 7:40 am

Hi Boyd - fantastic to hear from you again ;D

The colour variation that you put into the trees is great (and certainly blows my corrections out of the water)! There are two things that I think you could change though, that would make the correction even better:

Whilst the colour in your trees is great, some of the detailing is suffering. You can see where this is happening by layering your corrected version above the original file, and putting your correction layer into 'Color' mode. If you agree that the trees are taking too big a hit then try this:

  • Leave your correction layer above the original file in color mode

  • Create a new composite layer (Press Ctrl + Alt + Shift + E)

  • Apply the curve that I have attached (in CM), in Lab mode - obviously, please feel free to tweak it ;)

  • Create another composite layer (as above)

  • Edit > Fill - Use: 50% Gray/Mode: Saturation

  • Set this layer's blending mode to 'Luminosity'

  • Filter > Sharpen > Unsharp Mask - 30/17/0 (for the luminosity layer)

  • Filter > Sharpen > Unsharp Mask - 75/0.3/0 (for the luminosity layer)

Obviously everyone's taste in sharpening tends to vary, so you might want to alter the sharpening values that I have recommended here. Still, if you follow those steps, and then compare the result with what you've posted I think you'll be pleased :)

The only other thing that I think could use attention is the colour of the bridge (and its supports). The only way that I could get these areas neutral was by working on them separately with a mask. I used Stephen Marsh's 'Select Neutrals' Photoshop action (go to: http://members.ozemail.com.au/~binaryfx/ and click the 'Downloads' link to get to it, if you are interested). There are some colours in the bridge that need a bit more attention.

I've done both of those things to your version, and they make it look awesome - much better than my attempts.

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Postby ggroess » Sun Jul 25, 2010 2:58 pm


A couple of things...
Contrast...just a bit more helps the image have some weight...it also helps remove the "hazy" feeling your image has...

color in the bridge...Slight tweaks to the bridge make your image a bit better.  You can get rid of a large amount of the color problem.  Some red in the stone under the bridge on the left is acceptable since it actually could be that color...Fighting for absolute neutral is a great exercise but few stones are truly neutral....

If you apply the ACV file I posted to your image as posted you should see the changes easily.
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Postby imported_BoydMac » Sun Jul 25, 2010 5:07 pm

Greg and Lee,  Thank you both for your comments.  Greg, I've loaded your acv file and fully agree that the increased contrast adds alot.  I also found that I could completely get rid of the blue cast in the background hills by pulling the blue curve down a little at the 50% point.  Once I did that I decided that the blue cast added depth to the image and was a desirable feature.

The color cast on the bridge has been a real frustration to me as I said earlier.  Lee I tried to download the neutrals selector that you suggested but the download link no longer works.  Greg - your adjustment gets rid of an overall cast and it's not clear to me how you did it.  Nevertheless, there is now what I believe to be some posterized color cast (green) in the shadow areas under the deck on the right hand side.

Lee - I am going to have to spend more time than I have at the moment figuring out what you are doing about sharpening.  Can you point me to further references? 

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Postby mikemeister_admin » Sun Jul 25, 2010 8:01 pm

Hi Boyd  :)

When you follow the link, you might see a notice saying that the site is being updated. You can click on the link to get to the old site - the action is on there. I have attached it to this post though, just in case...

In terms of sharpening, I will assume that you are using Photoshop, rather than Elements - Greg is a much better source of advice about Elements than I am. Sharpening an image can create weird colour artifacts along high contrast edges (it looks like chromatic aberration), if you apply your sharpening to a coloured layer. Also, it is safer to create a specific sharpening layer (this enables you to fade back the opacity if you decide that the effect is too strong).

Therefore, when you want to sharpen your image you should create a new layer which combines all of the layers that your file already has (I call this a composite layer); you can do this by pressing Ctrl + Alt + Shift + E.

Having created this layer, we need to remove all of its colour. You can do this by choosing 'Fill...' from the Edit menu (Edit > Fill...). This will open a dialog box that will ask you which colour you want to fill the layer with - choose 50% Gray. Underneath this choice you will be asked which blending mode you wish to use - choose 'Saturation'.

These steps will give you a new B/W layer that combines the layers that you already have. I have attached an action that does this for you. Download it, open Photoshop, and then double-click it to install it. Let me know if it gives you any trouble.

Having a B/W layer also makes it easier to choose your sharpening settings. I would recommend using the Unsharp Mask filter to sharpen. Lots of other people like the High Pass filter, but it was never designed to be used for sharpening, and although it can look quite good, it is very destructive - it's best to avoid it (I will add a link to a website that will explain why at the end of this message). Nevertheless, the High Pass filter is the best place to go (in Photoshop) to visualise the 'Radius' value that will result in the best sharpen. So, my process is this:

  • Run my action to create a sharpening layer.

  • Select: Filter > Other > High Pass...

  • Choose an appropriate value in the High Pass dialog - more on this below.

  • Click cancel, to leave the High Pass dialog without making any changes.

  • In the Layers panel/palette, change the blending mode of the 'Sharpening' layer to 'Luminosity' - my action doesn't do this because it makes it more difficult to do the High Pass steps...

  • Select: Filter > Sharpen > Unsharp Mask...

  • Type in the value you decided upon in the High Pass dialog box into the 'Radius' field.

  • Select an appropriate 'Amount' value - usually you can ignore the 'Threshold' setting (for the sake of space, I won't explain it in this post, but please do ask if you're curious).

Ok, so how do you choose an appropriate value in the High Pass dialog box? This depends on whether you are trying to emphasise shape, or detail. There is no rule that you can't emphasise both. For instance, in the bridge image, the trees require greater emphasis. Emphasising shape basically means that we want to be able to see that one tree is in front of another, to create the sensation of depth. To make this happen in the High Pass filter, you need to use a large value - somewhere between 10-30 most of the time. In the case of this image I chose 17 - any higher and the trees start clumping up, with shadow regions loosing shape. Pick a value that is as high as possible without shape disappearing.

To emphasise detail (tree leaves and branches in this example) we need to do the opposite. Choose the lowest possible value in High Pass that makes these details appear (if the value is too low, for instance 0.1, the whole image will be 50% gray). In this image I chose 0.3. Don't be tempted to choose a larger value, even if it looks better in the High Pass dialog box preview.

Having chosen these values, open Unsharp Mask, and apply them in the 'Radius' field. Now you can choose an 'Amount' - which basically means the strength of the emphasising effect. When emphasising shape, the amount value should be low (the effect will be noticeable to you, since you are concentrating on it - but it shouldn't be obvious to viewers of your images) - in this case '30' worked well. When emphasising detail you can use larger amount values. The strength of the effect will depend on your output conditions. If you are going to be printing the image, the strength will need to look too high on screen (because ink spreads on the paper); if the file is for screen only just make it look as good as possible.

The caveat to all this is that the magnification level of the image preview should be 100% (unless you are using Photoshop CS4 or higher).

I'm more than happy to tell you more, but I'll add a few links in the meantime. Good luck ;)

Why High Pass is no good for sharpening: http://www.modelmayhem.com/po.php?thread_id=439098
Lynda.com Sharpening Video Training: http://www.lynda.com/home/DisplayCourse.aspx?lpk2=543
The best sharpening technique that I know http://www.bigano.com/index.php/en/consulting/40-davide-barranca/90-davide-barranca-notes-on-sharpening.html - be warned that this one is not for the faint hearted!

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Postby mikemeister_admin » Sun Jul 25, 2010 11:58 pm

I think there's a real color difference between the cable supports and the bridge understructure.I use the supports as a high value neutral in RGB and accept the bridge as a very light battleship blue-grey.Then I put another neutral on the concrete pier.GregM
Image 2 tried to keep the honeycomb detail to the lanterns
Image 1 nothing like a wall of sunwheels to draw the tourists in
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Postby ggroess » Mon Jul 26, 2010 2:38 am

Greg - your adjustment gets rid of an overall cast and it's not clear to me how you did it.  Nevertheless, there is now what I believe to be some posterized color cast (green) in the shadow areas under the deck on the right hand side.

My corrections to the image are mostly a modified version of the "By the Numbers" technique. Modified in that I was adjusting only the bridge and not a true shadow and highlight. The lightness values for the bridge are in a range that allows you to adjust them without adding a color cast to the rest of the image. 

If you look at the Curves this is the only set I used.  The "color worm" will tell you where you need to adjust to get rid of the color cast.  The changes are modest.  I tried LAB first and was able to make the color cast go away but was not satisfied with the rest of the image;  that was what told me I had to use RGB.  Once in there I set up the hue clocks where I felt I wanted the most changes and started working on "By the Numbers" from there...

Some things to note...The greens might also be JPG noise..I was working from your low res image posted not the full file..I am not certain and have not had too much time to look harder.  For instance I see some distinct reds in the bridge beams as well...  If I did push the greens that far; I missed that one...Sorry...and Good catch...You usually have to twist the curves up pretty hard to get to a posterized color  the "curve guard" usually lets me know all about it...


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