The animated gif above shows you what that distortion looks like in my favourite zoom lens, the Sigma 18-200mm DC. The middle of the image is clearly bulging out. The bottom of the sign isn’t straight but after correction it’s much better.

Unfortunately not every lens is supported. In the lens correction widget of Aftershot Pro you’ll see an “Uncalibrated Lens” message if your lens isn’t there.

Bibble 4 supported this lens and I only realised today that a bug in Bibble 5 and Aftershot identified the lens incorrectly and led me on a merry dance across the Internet. Bibble 5 and Aftershot Pro think my lens is the “Sigma 18-200mm DC OS” but my lens doesn’t have an Optical Stabilizer! Bibble 4 probably detected the lens correctly.

Unfortunately for me there’s no mention of “Sigma 18-200mm DC” in the “Canon Lens Table” or profile_canonlenstable.txt. Only the OS lens is mentioned and I presume the non OS lens was removed in Bibble 5 by error. Once I added an entry for my lens and added settings for the OS lens everything worked ok again.

Anyway, thanks to this ASP forum post and this Bibble forum post I was able to add my lens to Aftershot Pro. The nice thing about the lens database is that it is composed of text files that are easy to edit. I found a basic uncalibrated entry for the non OS lens. Unfortunately I didn’t search further or I’d have found the “Sigma 18-200mm DC” settings I wanted and saved myself some time! I created a new file called profile_mylenses.txt and added that filename to profile.txt.

First of all, I had to find the lens correction parameters that would fix things. The Bibble 5 post above links to sites that will help you figure out the correct a, b and c coefficients but thankfully I didn’t have far to look to find working figures.

I checked out PTLens first. It’s a programme that corrects lots of different lens distortions and it’s reasonably priced at US$25 per license. The author has shrewdly kept his lens distortion database in a secret format so I had to continue looking.

I then found LensFun, an open source tool to do much the same thing but using an older version of the PTLens database. The source is available so I went digging and found this interesting file! All the info I needed in one XML file!

All that remained to do was edit profile_mylenses.txt. In Windows and Linux the file can be placed in the following locations respectively. Mac OS X is probably in “Application Support” or somewhere obvious like that. In Windows you’ll want to use WordPad as the other profile files don’t have Windows line endings. You’ll also have to open it as an administrator to edit it.

C:\Program Files (x86)\Corel\Corel AfterShot Pro\supportfiles\Profiles\LensProfiles\
/opt/AfterShotPro/supportfiles/Profiles/LensProfiles/

After some editing and experimenting I found that these settings worked well:

begin lens
group: genericSLR
multiplier: 1.6
aperture: 3.5
menu_lens: Sigma 18-200mm f/3.5-6.3 DC OS
cal_abc: 18 0.018238 -0.045992 0.000000
cal_abc: 21 0.013683 -0.026594 0.000000
cal_abc: 24 0.007113 -0.008911 0.000000
cal_abc: 33 0.000000 0.010791 0.000000
cal_abc: 59 0.000000 0.012006 0.000000
cal_abc: 88 0.000000 0.010958 0.000000
cal_abc: 144 0.000000 0.008752 0.000000
cal_abc: 200 0.000000 0.007390 0.000000
end

I had to restart Aftershot Pro to test new settings each time.

If editing files like that puts you off you can create a preset to apply the lens correction. Click on the Manual tab in the Lens Correction widget where you can enter the a, b and c coefficients. Now go to the Presets widget and follow the instructions in my HOWTO: Add a copyright notice in Aftershot Pro tutorial except you’ll want the Lens Correction function to be active.

I suspect that these changes will be overwritten whenever I upgrade Aftershot Pro but maybe Corel will notice this little post of mine and they’ll fix the detection, or duplicate the settings in the next version..

While writing this post I found entries for the “Sigma 18-200mm f/3.5-6.3 DC” lens in profile_genericSLR.txt. Because the programme misidentified my lens it never used those settings. The 1.5 multiplier settings have the same settings as above, the 1.6 multiplier one is slightly different but there’s not much difference when applied to my test image.
Let that be a lesson to you if you’re trying to get this work. Look harder for an existing profile and make sure your lens is identified correctly! Argh!

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Martin, over at Photoakademie.eu created a workflow video showing how a photo was processed and eventually turned into a black and white image using Aftershot Pro.

Coming from a GIMP background I used layers and layer masks but never used adjustment layers to keep changes separate. Quite an eye opener for me!

Plus another demonstration of Aftershot Pro and a Google Plus account dedicated to sharing presets.

You can download a 30 day trial of Aftershot Pro here (I should be on commission for this..)

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This is what a simple copyright message will look like but you can change it to suit your own needs.

After you install zText find it in the plugins tabs and enable it, type your copyright notice and set the size appropriately.

You can adjust where the message will appear on the “Preset” tab of the plugin.

Once you’re happy with your copyright message hop over to the Presets widget and click the + “Add Preset” icon.

This window will popup, rename the preset to something meaningful and click “None” to unselsect everything.

Go into the Advanced tab and select zTextPlug and you should see the settings you already configured. Click OK.

Click the Show checkbox next to your new preset and the “Done” button on the Preset widget.

If you have an output job configured you can add the copyright notice as a preset in the job settings to automate the task every time you export a file. One advantage of doing this is your image in Aftershot Pro won’t have the copyright text making it easier to export it again using a different batch output job.

Hope that helped, want some more Aftershot Pro tutorials?

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This is the second article in my GIMP for Photographers series, but as usual, all of this applies to Photoshop, or any other image application with a Curves Tool. The first tutorial was on The Levels Tool, and worth a read if you missed it!

Here’s an image I shot at the Lord Mayor’s Picnic in Fitzgerald’s Park a few months ago, and the Curve Tool below it. Notice the histogram? The photo is fairly well exposed, but some highlights are “clipped”, as the histogram hits right hand side without sloping off.

Brightening Curve

It’s easy to brighten an image. Just drag points on the line up.

Darkening Curve

Now, let’s darken the image by dragging points down.

Contrast Curve

A classic use of the Curves Tool is to increase contrast in an image. You do this by darkening the shadows, and brightening the highlights. The curve looks sort of like an “S” when you do this. Don’t go overboard on this though, because it’s easy to lose detail in either direction.

If for some reason your image has too much contrast, a quick inverted S curve will solve that problem,

Wacky Colours

You can select any of the Red, Green and Blue channels and do strange things to your photos. Here’s what happens when you play with the Red Channel.

And here’s what happens when you change multiple colour channels in different ways.

Colour Picker

After you have opened the Curves Tool, click anywhere in the image. Notice how a vertical line goes up and down the histogram/line? That vertical line is the colour of the pixel where you clicked. That can be useful if you’re trying to modify a particular part of a photo. This is what you get when you click on the black coat on the left of the image above.

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Adam is 5 weeks old today! Last Wednesday we saw his first smile, or perhaps it was trapped wind because he was just after feeding but it was a beautiful sight to behold. He has smiled since too, and was especially cheerful this morning!

Adam loves his baby soother though. He sucks on it like Maggie out of the Simpsons does. Non-stop and with feeling!
If a soother or dummy isn’t nearby and it’s available, a hair dryer works wonders for relaxing him. The sound soothes him and he can go from screaming the house down to docile and a gurgling baby in seconds when the hair dryer is switched on. It’s magic.

Technique: This is a high key portrait created using two layers.
1. Original image is the bottom layer.
2. Duplicate that layer.
3. Convert top layer to b/w using channel mixer.
4. Apply Gaussian blur to the top layer. I used a 75 pixel wide blur.
5. Change mode of top layer to screen.
6. Add white layer mask to top layer and reveal eyes from original image by painting over them with a black brush. Use an opacity of 10%.
7. Merge layers and save. Layers should be separate when resizing so you can unsharp mask the bottom layer.

Hope that is of use!

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The tide is out in Cobh, Co. Cork while the sun sets in the west casting an orange glow over the water and boats in the harbour.

Method
This required some work to expose properly. The sky is bright while the harbour, houses and landscape are in shadow. Out with the layers, top layer for the sky was darkened and the opposite was done for the ground.
Then it’s the simple task of adding a layer mask to the top layer and rubbing out the dark bits to expose the brightened landscape.
When using a layer mask, never paint with an opacity of 100%, try 30% or even 5%. Don’t be afraid to do a rough job of exposing the bottom layer because with a layer mask you can always reverse the procedure by swapping the colour of your brush with an opposite colour!

Thank you all for the comments on yesterday’s post, The Lonely Swan, it’s great to get feedback and I’m glad when people get something out of my methods when I describe them. See what you’ve done? I did it again!

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Hover over the image below to see what the original shot looked like. Hopefully this will work for RSS readers but if it doesn’t, visit the blog and leave your mark here!

Notice how I rotated the image? I had to reconstruct the bumper on the right of the picture, as well as filling in the gaps at the other corners of the photo. Tree branches and leaves are easy enough, as is the relatively solid black texture of the tar on the road, but the bumper was difficult, and the shaded area of the building on the left presented me with a few extra minutes of clicking to get right.

Want to see more “First Draft” posts? I can’t promise to do many, but if you have a compelling reason why you’d like to see the original of a photo I’ll do my best to help!

PS. Bryan – you might recognise the CSS. I took it from the button of doom you did! Hope you don’t mind!

PPS. Treasa has posted a tutorial of how she worked on two photos with steps in Photoshop to get the desired effect. Nice!

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I know I won’t need it when I’m outside tomorrow, but Strobist linked to a professional lighting setup for portraiture in a studio. Might come in handy later.

The venerable Philip Green’s portrait page is of course a good read. It’s been around for years and I’ve read it many times. If you haven’t browsed http://www.photo.net/learn/ yet then you’re missing out!

Finally, Anandtech’s Portrait Tutorial is good, includes examples but I wonder why their second photo was included. The poor girl has stone columns coming out of her shoulders, even when blurred!

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Another great resource is Photonotes: Eos Flash for users of Canon cameras and flash units. There’s some great bits of info there.

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There is so much distortion because the camera is rotated around using a normal tripod or worse still, handheld. The axis around which the camera is rotated is centered on the camera body usually, but a panoramic tripod is different. The center of rotation should be the lens of the camera, specifically the “nodal point” of the lens where light paths cross before hitting the camera’s film or sensor.

Make Blog links to a tutorial on building a panoramic tripod head for $10! That’s a lot more reasonable than what you’d pay for a head from Manfrotto or manufacturer. It probably isn’t quite as portable or nice looking though and you might have to invest in some tools to cut the wood and build it but it would be an interesting project.

If that’s too complicated, you can build a battery using a bit of wire, a screw and a magnet!

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