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Scubajack

Caribbean Reef Sharks

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Any comments or suggestions welcome. Trying to learn.

 

All were shot with a Nikon Coolpix 5000 in a Tetra housing;

BTW, I know most of you don't like the frames, so no need to comment on that. It's the way we post them on our site and it's easiest for me to post them here with the frames.

 

 

shark-profile.jpg

 

shark-duo.jpg

 

shark-%20remora.jpg

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Very nice composition. Where did you photograph these guys?

 

For my personal preference, I would deepen the blue water background and slightly increase the contrast. I played with the photos briefly, and found that Auto Levels made a nice difference. Just a personal preference.

 

 

Jim

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These are some very nice shark images. I think you could do more in PS to optimize the appearance - the second and third, in particular, are excellent candidates for playing around with channels. The best tool for this is the A)pply I)mage feature in PS, which works like the Channel Mixer, but is more powerful.

 

If you look at the individual channels on the second image, for example, you'll see that the red plate is very weak. That's the cause of the cyan cast pervading the entire image. You can also easily see that the weak red channel contains most of the noise that slightly degrades the overall image. Dumping it can actually reduce noise and yield a sharper, cleaner image.

 

Here's a quick example of the kind of thing that can be done. I just took your image, dumped the worthless red channel, and replaced it with a copy of the green channel at about 80% opacity and hard light blend mode. That, and readjusting the contrast in L*a*b curves, took about one minute..

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Scubajack,

Very nice shark images. I like the third one the best, given the pose and the fact you got the whole shark. I also like the PS enhancement Frogfish was able to achieve.

 

Here's a quick example of the kind of thing that can be done. I just took your image, dumped the worthless red channel, and replaced it with a copy of the green channel at about 80% opacity and hard light blend mode.   That, and readjusting the contrast in L*a*b curves, took about one minute..

 

Frogfish,

If I may, I'd like to ask a few questions about what you did. I'm relatively new at PS and trying to learn through this and other forums. I tried to duplicate your results based on your explanation but couldn't. I did try to find my way around AI (my first time using it), and nevertheless came up with a fairly decent result.

 

1) When you dump the red channel, is that by choosing Red channel in AI, and then choosing exclusion, opacity 0% ?

 

2) How do you replace the red channel with a copy of the green channel ? (Do you end up with two green channels ??) I simply selected the existing Green channel and used hard light blend mode with opacity about 40%.

 

3) What are the L*a*b curves ? I adjusted Levels and then brightness/contrast.

 

I apologize for all the questions, and I hope I haven't hijacked Scubajacks post! If you'd prefer to PM me with any comments, that's fine by me.

 

Many, many thanks.

Cheers.

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Scubajack,

 

I've written a Feature piece about channel mixing techniques, but it's still in the queue. In many cases, you can use the channel mixer for this, which is easier to use. But Apply Image is more powerful, in that you can select different blending modes. Lighten is often the best for situations like this shark.

 

One way to dump the red channel (the one I used) is to click on that channel on the channel palette, Select All, then Clear. The channel should go completely blank.

 

To bring in a copy of the green channel, keep the red channel selected on the palette menu, but click on the left column next to RGB. This way, you can see the compiled image, but Apply Image (and any other operations) will only affect the red channel.

 

When you start Apply Image, the red channel should already be identified as the target of the operation. Just switch the source to the green channel. Now you can play with different opacity levels and blending modes, while viewing the results on the screen. When you get what you like, click OK. That's it.

 

L*a*b is an alternative color space, with a much larger gamut than RGB. It's also used as the base color space for a lot of Photoshop operations. If you convert your color space from RGB to CMYK, it actually goes through L*a*b on the way.

 

L*a*b may seem difficult, but it's well worth learning about. I talk a bit about it in the feature piece. If you take an image, and go to Image, Mode, you'll see Lab as one of the options. Click on it, and now the color channels of your image will be the Lab channels: L (luminosity), "a" and "b". The L channel contains all the luminosity data - is essentially a black and white image. The "a" and "b" channels have all the color information - "a" values represent a contimuum from red to green, while "b" values represent blue to yellow.

 

You probably already know about curves, which is an alternative to Levels, but more powerful. It does everything Levels does, but much more. Curves can be used in RGB space, but are particularly powerful in L*a*b space.

 

If you modify the L curve, you can change the contrast, brightness and/or darkness levels of the image without affecting color at all, which can be difficult using RGB channels. Steepening the L curve increases contrast, and moving the ends in the opposite direction does the opposite.

 

Modifying the "a" and "b" channels is often the best way to correct a color cast, and can also be used to modify saturation levels selectively at different parts of the curve. Steepening the "a" curve will increase saturation of both reds and greens, moving both ends in the opposite direction will desaturate reds and greens. Shifting all or part of the "a" curve up will increase red values (and remove a green cast), shifting it down does the opposite. Similar for the B curve with yellows and blues.

 

Make the Curves window as big as possible, since a small change in these curves can make a big difference in the image. I usually find it easier to make color and contrast corrections in L*a*b color space.

 

Hope this helped.

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Frogfish,

Many thanks for taking the time to post that. I'll give it a try. I look forward to reading the Feature piece.

Cheers.

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