Parrotfish and Deep Focus

Posted in Under the Sea on May 30th, 2010 by MadDog
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Saturday dawned brilliant and promising. I was looking forward to going back to The Eel Garden near Pig Island  to find the Leafy Sea Dragon which has been reported to be on the old catamaran. I looked in vain for it last week, but a fellow diver, Hendirck, told me that he had found something promising. In return for the information, I dragged out my old Canon G10 and its underwater housing for him to try out.

Unfortunately, with all of the juggling around of cameras, housings and memory cards, I managed to show up at Magic Passage for our first dive with my G11 showing “NO MEMORY CARD”. Ai ya yai ya yai!  Stupido!  So, I did a very nice dive on which some very interesting critters were spotted, but I had no camera.

Never mind. I pretended to enjoy it, playing Divemaster and pointing out all sorts of fascinating items which I determined to burn into my brain memory cells instead of my usual memory contained in my camera. The camera is much  more reliable.

On the second dive at The Eel Garden, Rich Jones was not diving, so I used his new G11 which was out on its virgin underwater experience.

There were many very colourful parrotfish about. This is simultaneously exciting, euphoric and frustrating. If you are a snorkeller or diver you understand the first two. If you are an underwater photographer you get the latter. Google parrotfish and look at the sad offering of images. It is nearly impossible to get close to them. You must depend on the occasional quick shot when one darts past:

I don’t know the species of the one above. My fish book is at the office and I have photographed so few that I can’t remember most of the names.

This one, I do know, but I would call it a “failed” image:

It is a Hump Head Parrotfish (Bulbometopon muricatum).  They are huge. This one was at least 1.5 metres long. Unfortunately, they are delicious and easy to spear. In some areas of the South Pacific they have disappeared completely. This was a quick snap shot at the end of a long tiring chase during which I managed to corner it long enough for a very poorly framed image. The closer you get to them the bluer they look. I was about two metres away from this one in fairly dirty water.

I’ve been playing around with a photographer’s technique called “deep focus”. It sounds exotic, but it is easy to understand. The smaller the hole you are looking through, the more “depth of field” you will get. In other words, objects from near to far will be in focus if the hole is small enough.

Theoretically, a pinhole will have a focal range from very close to infinity. So, the larger the number of the f-stop you use on your camera (the size of the hole through which the light passes) the smaller the hole will be. I know it sounds backwards, but never mind. Big number – small hole  – more depth of field. That’s the way it goes. If you can get f 16 on your camera, you will get lots of stuff in focus from near to far. At f 2.8 you will get only near or far, but not both.

It works better for non close-up stuff. For instance this shot of the Nudibranch Phyllidia varicosa  doesn’t show much effect:

Sure, most of it is in focus, but there is not much to show the depth of the image. There are no obvious visual clues to indicate depth.

It this shot of coral with an anemone in the background, however, there are many clues to indicate distance:

It requires a lot of light to use the small lens opening, because not much can get through. If you don’t have enough light, you will be forced to use shutter speeds that are too slow to give sharp images. There’s no free lunch. You can have it one way or another, but not both. I manually blurred and darkened the very distant objects at the top to enhance the effect.

In both of these images I failed to note that when I changed the mode of my camera to Aperture Priority (meaning I get to set the aperture and the camera automatically sets the shutter speed) I lost my format setting and it reverted to JPG. I always shoot underwater in the RAW format mode because it allows me much more colour control. Sorry to bore you with these arcane details, but there are a few photographers out there who are constipated enough to care about these things.

Here is a pretty scene, never mind the colours are off, of some coral with Purple Antheas swimming around:

It nicely illustrates the reality which you can get with the deep focus technique.

Okay, that’s it for me. It’s Sunday evening. The sun is below the yardarm. I’m going for a wee dram and lay on the bed to watch some mind-numbing TV for a while. Then maybe I’ll rest my eyes for a bit.

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Bite Me Red Fish

Posted in Under the Sea on December 3rd, 2009 by MadDog
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Sometimes it’s more difficult to think of what to title a post than it is to write it. Yesterday’s The Big Blue Finger is a case in point. Today’s title is even more illustrative. I have a bunch of stuff to show you. It has no theme. What can I call it. I’m getting tired of trying to incorporate the word ‘miscellanea’ into a title. There’s only so many ways to do it. So, Bite Me Red Fish. As you shall see, the red fish doesn’t bite and the bite marks have nothing to do with the red fish.

Okay, okay, I’m obviously rambling now. Let us proceed to an image that I should have deleted, but it’s the only picture that I have of a Solor Boxfish (Ostracion solorensis):Solor Boxfish - Ostracion solorensisIt’s a shame it’s such a bad picture. It is very difficult to get close to them. This one was scurrying frantically to get out of sight when I saw it, so I just pointed the camera and snapped, not even knowing if I had focus or even if the fish was in the picture at all. When I got home and opened the image in Photoshop, I could see that I got a lot of smear from the very blurred image caught on the sensor while the shutter was open and one nice, sharp image of the fish when the flash went off, both on the same exposure. This is a problem that I can’t fix on the Canon G10, I think. There’s no way to make the shutter speed faster than 1/60 second when you have the flash turned on. So, you get a partially blurred image with a crisp flash capture over the top of it, so to speak.

Well, I’m sure that that explanation put a lot of people to sleep. How about some poo?Sea Cucumber FecesYou can now state proudly to your friends and neighbors that you know exactly what Sea Cucumber poo looks like. A surprising amount of it comes out of them. I guess it’s not so surprising when you consider that most of what they ingest is plain sand. You have to suck a lot of sand for a bit of nourishment.

I should call this one Death Takes Us All:Empty Bivalve ShellThis beautiful little bivalve has met its doom recently. There hasn’t even been time for much sediment to fill its empty shell. This shell is about 4cm long.

Now for the bite bit. Hard coral is . . . well, uh . . . hard!  You will know for certain the first time you bang your head on it. If you’re a photographer, it will happen sooner or later. However the marks you see here were not made by my pointy, pointy head:Parrotfish Bite Marks on CoralNo, those marks are the result of normal parrotfish feeding habits. This coral is not as hard as cement, but pretty nearly so. Therefore, you can imagine how hard the teeth of a parrotfish must be. In this case it was a rather large one. The bite marks here are about six or seven cm long. Thank heavens that parrotfish are not inclined to include humans on their menu.

So much for the bite. How about the red fish? Well, in that contest, the Scarlet Soldierfish (Myripristis pralinia)  has little competition:Scarlet Soldierfish - Myripristis praliniaI don’t know what is the origin of the common name, Soldierfish. They all have pretty much the same general form, including the big, big eyes for most of them.

It is interesting to me that, although I usually complain that using flash makes everything look redder than it does in nature, I have to say that it didn’t hurt the representation of this species. The overall shot is warmer that I would prefer, but the fish itself really is that red.

And, it doesn’t appear to be inclined to bite me.

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