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ATJ

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Everything posted by ATJ

  1. I frequently go to my 18-55mm when I know the viz is not going to be great and I'm diving a site with a range of subject sizes.
  2. I managed to find a quarter in a drawer so here are a couple of photos to show size.
  3. I have a Citizen Hyper Aqualand and a Citizen Cyber Aqualand NX. The Hyper Aqualand was bought in 1999 and is still going strong (the battery has been replaced 2 or 3 times). There's no computer but it does log depth and temperature. The data can be transferred to a Windows XP (or older) computer. Now that I have the Cyber Aqualand NX, this gets mounted on my camera rig as a backup (and holds the sync cable in place). The Cyber Aqualand NX was bought on 2005 and is also still going strong. It has a computer and also does Nitrox. This is comfortable to wear on the wrist and when I do dive trips is my 24x7 time piece. The Hyper Aqualand (or whatever the current equivalent) is smaller than the Cyber Aqualand NX - about the size of a regular watch. It makes a great everyday watch. The Cyber Aqualand NX is a bit chunky but would be OK as an everyday watch and works fine for that purpose for me on dive trips. By the way, I have very small wrists and neither watch gives me a problem.
  4. There is no worry at all. This side discussion stemmed from Dave being smart with the thread title...
  5. Wavelength is inversely proportional to frequency (and vice versa). If frequency affects speed, so does wavelength. In a vacuum, wavelength/frequency do not affect speed. In other media, they do affect speed depending on the refractive index of the media. The refractive index of a medium varies with wavelength which causes dispersion and is why we see rainbows (refraction and dispersion of light through water moisture in the air) and also chromatic aberration in lenses. As different media have different refractive indexes, the speed that light passes through those media changes. If the speed of light in a vacuum is c, the speed in a specific medium is v = c/n, where n is the refractive index of the medium. Air has a refractive index slightly higher than 1 (1.000293 at 0ÂșC and 1 atm according to Wikipedia). For water is is around 1.333. Temperature and pressure can also affect the refractive index which is how we see thermoclines. Lens (cameras, spectacles, eyes, etc.) work because of the variation in speed of light as it moves from a medium of one refractive index to a medium of another. If the light passes through perpendicular to the interface, the light follows a straight line. If it passes through at an angle, it is bent (refracted) and the amount of bending (refraction) depends on the refractive index. Even dome ports work because of refraction, mainly from the difference between the refractive index of water outside the port to that of the air inside the dome port. So... if the speed didn't vary with media, refraction would not occur and we wouldn't be able to see the way we do and pictures wouldn't work.
  6. You could, certainly. The main benefit of more manual settings (or using TTL) is that you have more flexibility with the aperture at which you shoot. Aperture determines depth of field so with more manual settings for the strobe you have more options for DOF.
  7. Read the rest of that post. The part about the 3 conditions.... Additionally, the OP was worried about freezing action...
  8. How are you viewing the images on your computer? How are you viewing them online. One possibility is colour management. Some browsers, e.g. Internet Explorer don't do proper colour management and so won't display your images correctly, especially if you have an embedded colour profile. Firefox does do colour management but it is not always on by default.
  9. Sorry? Who's overreacting here? I was simply clearing up a misunderstanding. Seems you are the one that needs to relax.
  10. One concern (and probably a pretty major one) I have about the use of red focusing lights is the contrast to strobes. If the organisms truly are less sensitive to the red light (and it appears not all are) then they won't "see" the focus light and won't react to it. How much worse, then, are the strobes firing? Sure, you're more likely to get your shot, but what is the impact on the organism? Now, if you're using a white focusing light, at least the difference between the focusing light and the strobe will be less.
  11. And the medium through which it is traveling. (For photography, the latter is VERY important.)
  12. The manual for my Nikon SB-800 Speedlight lists: 1/1050 sec. at M1/1 (full) output 1/1100 sec. at M1/2 output 1/2700 sec. at M1/4 output 1/5900 sec. at M1/8 output 1/10900 sec. at M1/16 output 1/17800 sec. at M1/32 output 1/32300 sec. at M1/64 output 1/41600 sec. at M1/128 output I would expect most strobes/flashes to be similar. I doubt many if any get longer than 1/800s. The manufacturer should be able to tell you the approximate durations.
  13. I'm guessing your camera has a maximum flash sync speed of 1/160s. You would only be "stuck" with 1/160s if you were using a flash/strobe to take the photo. If there was enough available light, you wouldn't need the flash and you'd just set the camera to whatever shutter speed you wanted. Now, I assume you are using the flash because there isn't enough available light. There are three general situations where this would be the case. 1) The flash is pretty much the only source of light. 2) There is some available light but the flash is still the primary source. 3) You are using the flash to fill certain areas but still relying on the available light to expose most of the scene. In 1), you can pretty much ignore the 1/160s of the camera as this will have almost no effect on the image. The effective shutter speed will be between 1/800s and 1/20,000s depending on the flash and the power setting. Note that when using iTTL/eTTL, the strobes are basically quenched when enough light has been received so it has the same end result as manually setting the right power level. Even 1/800s is going to be fast enough to freeze most action, especially under water. For 2), you will get similar result to 1) unless there is quite a lot of available light. If you are shooting a subject relatively close to the camera, you can use a smaller aperture which will decrease the effect of the available light and so you may still be able to achieve relatively fast effective shutter speeds. 3) is the difficult situation with fast moving subjects. The 1/160s of the camera shutter is going to let enough light alone to expose an image and you're likely to get some motion blur. What you can do, however, is set the camera/strobe to rear curtain sync. Remember I was talking about the leading and trailing edges of the shutter? With rear curtain sync, the flash is synchronised with the trailing edge of the shutter (rear curtain) and so the flash effectively goes off at the end of the time the shutter is open. This will give you an image that is sharp and frozen from the flash, but with motion blur leading to the frozen image. i.e. it gives a sense of motion in the still image. You won't have frozen the motion, but you can have a pleasing image. It is usually listed in the specifications of the strobe.
  14. Flash sync speed is more about the shutter on the camera and has little to do with the strobe and how long it is on for. The shutter on most modern cameras is actually two parts that slide across or down over the sensor. The leading edge "opens" the shutter, exposing the sensor and the trailing edge "closes" the shutter, stopping the sensor from being exposed. If the shutter speed is slower (longer) than the flash sync speed, the trailing edge does not start its pass until the leading edge has already completed its pass. If the shutter speed is faster (shorter) than the flash sync speed, the trailing edge starts to "close" the shutter before the leading edge has finished "opening". At any point the whole sensor is not exposed at the same time, i.e. it is a smaller window passing over the sensor. Because the flash duration is so short (even on full power) only part of the sensor would get exposed and part of the image would be underexposed or black (depending on the ambient light).
  15. Does it really matter? Surely people will continue to use what works for them - or at least makes them happy or money (whatever their goals may be).
  16. Note that no-one in this thread suggested that weedy seadragons have been seen at Shiprock. I have certainly never heard of it and would be extremely surprised if they have ever been seen there.
  17. I loath diving without a camera however it can still be better than not diving at all. I went to Borneo last October and my main aim of the trip was to see and photograph flamboyant cuttlefish. I had never seen in nature before but they are my favourite underwater creature. Within a couple of hours of us arriving at Kapalai we went on a "check dive" on the house reef. There was not enough time to get my camera ready so I went sans camera. Five minutes into the dive I spot a flamboyant cuttlefish ambling across the sand. I was rapped to finally see one (I think I even cried). I regretted not having the camera, especially if this was the only one I'd see for the trip but I was also very pleased that I had seen one at least. I did another 21 dives on the trip and only saw one other flamboyant cuttlefish (1st dive of the next day) and I got photos. It so very nearly happened that the one on the 1st day was the only one. I would have been really annoyed that I hadn't got any photos but I still would not have traded that dive for anything. Seeing one was 95% - getting photos was icing.
  18. It is also a good idea to experiment out of the water. First, become familiar with the camera outside the housing so you know what all the controls do and you can play with shutter speed and aperture and see what effect they have. Put the camera in the housing and hook it all up to the strobe and play inside the house or even in the backyard. Again, see what effect shutter speed and aperture have on the shots. Set up some static subjects to use. The better you know the camera and what effects different settings have, the easier it will be when your task loaded underwater.
  19. Here are some samples from Shiprock from 2011 alone (and only up until August).
  20. While viz is important, it isn't everything. Seeing a vast array of organisms on a single dive with ordinary viz is far better than 50 metre viz and seeing nothing. Shiprock is an estuary and so will never have viz as good as some of the ocean sites, although, when conditions outside are bad, Shiprock can actually have the best viz for all of Sydney. The appeal of Shiprock is the amount of life there. The wall is covered with soft corals and ascidians and the soft corals are all over the bommies, too. It is rare that you dive there and don't see: pineapplefish, frogfish (the real ones), triplefins, moray eels, cuttlefish, octopus, numerous nudibranch species. There's also a good chance of seeing wobbegongs , Port Jackson sharks, numb rays and other interesting organisms. But each to their own, I guess.
  21. http://www.abc.net.au/news/2012-02-29/reef...erwater/3861036
  22. That may be a factor but it can't be the only thing. I could check two bags, each of 15kg and they'd charge me for being over my 20kg limit by 30kg. i.e. they are charging me for my total checked baggage not the fact that one bag is overweight. I have been told it is because of the increasing cost of fuel and if it is, then a lighter person shouldn't have to pay the same as a heavier person.
  23. I agree with John's starting settings of ISO 200, 1/125s and f/11. With the D70 you don't really want to go higher than ISO 200 as the noise will get too noticeable. Use the camera's light meter display in the viewfinder to help you determine what will happen with the background. Ideally, you want it to say anything from slightly underexposed (which will give you a lighter background) to grossly underexposed (for a black background).
  24. Shiprock. It is currently closed at the moment (has been since August 2011) while the council install some proper stairs and other things. It was supposed to be open by Christmas, but it is the council after all. Their latest update says early March, weather permitting, which given all the rain we've had, will probably slip. It should be open by May, but then again... In my opinion, Shiprock is the best dive site in Sydney and well worth a dive, day or night. My second favourite site is The Leap at Kurnell on the southern side of Botany Bay. On one dive you can see giant and reaper cuttlefish, seahorses and weedy seadragons, Port Jackson sharks, anglerfish (AKA "frogfish"), many species of nudibranch, moray eels and more. Shelly Beach is an OK site but you'd have to do it mid-week. On the weekend it get so many dive schools that sometimes it is hard to see the water for divers.
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