digital blending..underwater

Hi folks,

I often ask a lot of questions on this forum for my own benefit, but I'll admit I have posted a few to help other as well. I am too lazy to search the site as to whether this topic has been covered or not, but here it goes.

And I'll admit that I have yet to try this underwater but I thikk it will work in some cases, specifically for underwater.

I was at a national park at a place called Tonto Bridge in Strawberry AZ. It was beautiful, but some areas were too bright to get the dynamic range I needed. The sky was either white and forwground properly exposed or vice versa, but I could not get both. Even with the shadow/highlights tool, it was too much. So I read up on digital blending where you take two shots of the same thing using a tripod. The first shot I expose for the sky, the second for the foreground. Then I blend the two together and make some adjustments an ulala. Nice shot. Got some nice shots as a result. I purchased the Fred Miranda dynamic software but was a little dissappointed at the results in some cases. So I experimented, asking myself, "how can I make this work underwater?".

Here is what worked for me.

I shot mid-range pictures...getting basic shots in the tonal range where neither the negative space was blown out (but somewhat hot) and the foreground was peeping some detail. Then I did two things.

1. I used PS levels and shadow/highlight to slightly underexpose the image, giving me a nice negative space (in this case good sky color). I saved it as "dark.jpg"

2. Then I did the opposite. I readjusted the ORIGINAL image for the foreground (the leaves under the water) and basically blew out the sky. I saved this file as "light.jpg."

You can do two things. Use FM to blend them or blend them yourself. You can go to luminous-landscape.com for the specifics on how to blend manually. This is where FM software is effective. When you use FM, you can then make other adjustments as needed. Blending on your own as perscribed by luminous landscape is tricky, as they state.

I am not posting this to be an all encompassing directional 'how to' but to tell all of you that using the very same picture (as opposed to 2 separate pictures) is easy and effective. I want to try it underwater, but I am stuck here in Pennsylvania for a bit, where I am freezing.

Please feel free to ask questions, though.

Kind regards, Joe Belanger

If you havent allready, try shooting in RAW. Convert two files from the RAW, one you push up, the other down. By pushing the exposure before converting you retain more detail in the the shadows.

You have a great point but personally raw has not shown me anything different than JPG when you have PS shadow/highlight. I admit that this technique is new to me, and raw has been something I have not liked (or dont know how to use) simply because it is no different to me. I can adjust JPG almost in the same fashion as raw. I recently shot a wedding in JPG and RAW and when adjusting the pics, I can get the same results with JPG. However, I have not blown anything up and really cannot speak to quality of JPG versus RAW.

It's not me being resistent to your comments, it's me being unknowledgeable about how to work with Raw. I have tried raw using PS CS, but coulod not determine what the advantage was.

I am very open to your feedback.

Joe

I think RAW is probably best used in challenging environments.

For example shooting underwater where gobs of light are needed and the ambient light has most of the color filtered out. In this case the ability to adjust exposure and white balance after the picture is taken is invaluable.

On land it may not matter, particular for weddings etc. But I wonder what nature photographer use? Anybody?

HI Peter and all,

What I was saying in my post was that you can use the same underwater picture to get the results (assuming you have a good exposure to work with), Lets say that you have wide angle picture that looks good, but the coral is dark and the sun lit water looks great. I am referring to a situation in which your foreground (coral) is near brown, but the blue water is blue, the blue you want. You have 2 medians....one that works and one that doesnt. Even in raw, you cannot adjust exposure to get both in alignment. Thats what I am debating. I can get both in adjustment but making two pictures of the same thing. If you can use raw, EXCELLENT! I am simply proposing another way to get a nice pic if raw wont do the job.

The idea of raw by my fellow photographer is an important piece you must consider. The beauty of digital is that if one does not work, try the other.

Joe

The most dynamic range a JPG can contain is about 7 stops. A 16 bit TIFF, on the other hand, can contain more than any current RAW file can produce. 10 stops is now possible, up to 14 available. If you think that you can achieve wide dynamic range by manipulating a single JPG in any way you're mistaken. 7 stops is it. To do better you need RAW or multiple exposures.

It suprises me that people believe they can get wide DR with a single exposure through blending. All the data is contained in one exposure so you can't get any better. Instead, blending accomplishes unusual, piecewise applications of tone curves over the dynamic range that you already have. It's a useful technique and one that I've used underwater, but it does not result in wider DR that people believe it does. Ultimately we compress whatever we have down to 7 stops or so since that's (a) what our eyes can see, and (B) that's what our output devices are capable of. Usually our output is less than that.

BTW, I like this technique for surpressing backscatter in troublesome images. You deliberately underexpose a conversion for the background, clean it up, then properly expose the subject and blend it in. Not saying I've ever done that, but...

Hi Craig,

You are correct in your statement. I did mis-speak regarding DR. Actually, I am using words that I totally do not understand yet. What I am really saying is that you can use the same technique, albeit not true DR, to greatly improve an image, especially JPG. I need to shoot some raw files and experiment. I need a beer.

Thanks for the feedbackand clarification.

Your diving buddy, Joe

You're right, it's a good technique for improving some images regardless of how they are shot. Can't create extra DR though unless you take multiple exposures.