Jump to content

U/W photography links

Achilles Tang

By Achilles Tang,
in General Reefkeeping_

 Share

Recommended Posts

Achilles Tang Newbie

Achilles Tang

Posted
  • Author
Posted

Extracted this nugget of info from a diving forum:

Selecting an external flash is not that complicated. The thoughest part is making your mind on how you wish the external flash to be triggered. To my knowledge (limited) there's right now no housing that will allow a strobe to be directly connected to one of the digital cameras you're considering. From what I understand the beautiful Tetra housing for the S400 uses the internal flash of the S400 and has it's own circuitry to make the external duplicates the internal one. Matthias Heinrichs adapter and the Ikelite D-TTL slave sensor use a similar approach. I can't tell you which one works the best. Tetra housing claims to work with many strobes, Mathias adapter works with almost all Nikonos strobes and many Sea&Sea, finally I think the Ikelite sensor only works with the Ikelite DS-125 and DS-50 strobes. The other way to hook up a flash to a camera is to use a flash that is triggered by the light of an other one. That's what we call a "slave strobe". So the internal flash of your digital camera fires and the slave strobe senses it and do the same. This set-up is not fool proof and the slave strobe may miss the reflection of the camera strobe or trigger on the sun in shallow water. So when it is use as a main flash triggered by a camera flash people will use a fibre optical cable linking the internal flash and the integrated slave sensor on the slave strobe to improve reliability. The current problem with this set-up is that many digital cameras use a pre-flash to evaluate how much light should be really delivered to properly illuminate the subject, so most of the slave strobes sense this pre-flash and drop their full power. Right now, only a handful of strobes have the appropriate circuitry to ignore the pre-flash and wait for the full flash so that they could be synchronised with the camera. Sea&Sea has the YS90-DX and the YS-25DX, Ikelite has the DS-125 and the DS-50 finally Inon has at least the D-180.

The main advantage of the first approach is that you get a TTL behaviour. It means that the camera controls the flash and stops it when the sensor has received enough light. The term TTL means Through The Lens and refer to how film cameras control their flashes. Some of the light that reach the film is reflected on a sensor that allows the camera to quench the flash when enough light has reach the film for the selected aperture and speed. This is not fool proof if you have a subject that reflects or absorbs too much light or if the subject doesn't cover a fair amount of the field of view. But most of the time you will get good results and it's a bonus when you start shooting underwater.

The second approach works fine too, but you have to know how much power your flash delivers at a certain distance and to select the proper aperture for the selected ISO (you don't have to bother about the speed because as long as your flash synchronise for a given speed the flash duration is shorter than the speed). To help you find out the appropriate aperture all the strobe have a guide number (GN). For example my YS60 has an underwater GN around 32, so it means that at 3 feet and f/11 I should get a fair exposure at ISO 100. You multiply the n number by the distance and it should be close to your strobe GN. GN can be either expressed in m or ft.

In a nutshell you are correct in assuming that you can add a strobe later. And indeed you can enter the shop and ask "Fix me something for this camera". The shop owner will probably open his/her gorgeous Sea&Sea catalogue and suggest you a YS-90DX or YS-25DX Digital Lighting Package that includes a strobe, a fibre optic synch cord, a stay and an arm for the 2003 MSRP of 856.95$US or 588.95$US.

So we are back to your original question: Which camera should I choose from the A70, A80, S-400 or G5? and here is my two cents worth about it.

1- You have not yet experienced UW photography, it takes a good (and I should have said excellent) buoyancy control and enough experience to loose an arm to take care of your camera. Some people find that is close to task overloading and drop out. The first tries are usually awful and you need to have some perseverance. But if you are at ease underwater, like photography and the marine environment you can't find a better hobby.

2- You can get decent results with ambient light at shallow depth with custom white balance or with a filter. Moreover I have to admit after seeing some shots from a member of this forum (bharvey) taken with his S-45 and the internal flash with a diffuser that the internal flash may give you very interesting results and should be tried if the water is very clear. I'm assuming that you won't shoot in our cold and murky Canadian waters. BTW were in the world are you diving in Saskatchewan? And before starting a flame thread NO our Canadian waters are not that murky! But they are cold. I can't figure out myself trying to depress the small buttons of the WPDC-700 case with my mitts in the 1C degree (34 F) water of Les Escoumains in the St-Lawrence River even though it's a paradise for an UW photographer.

So unless you intend to buy a digital SLR in one or two years (or lapse of time you consider a near future) I would suggest you to buy the camera you consider the best. It will be the backbone of your set-up.

The G5 has the maximum resolution and features, provides you with the closest focus range in macro with Tele, has RAW storage capabilities to name a few. I would personally consider it the best of the pack you have pre-selected. The only thing it may gives up to the S-400 and A80 is the size of the pixel. These two cameras have the same 1/1.8" sensor size but the G5 has more pixels on it. Hey how about the G3? This should have an impact in low light situations but I have not seen any reports about that yet. It's a more expensive set-up once you have added the housing but you get more for your money.

If you are not sure about digital photography or just want to get your feet wet at it before spending more money on the real thing, in my opinion nothing can beat the A70. It is user friendly and packed with features not found on more expensive cameras. You can get nice 8x10" from you best shots at maximum resolution. I would say that the only features I regret not being on it is a RAW mode and a larger sensor. I didn't hesitate to select it telling myself that it will always be the camera you're carrying everywhere for snapshots. Remember in comparing prices that you will have to buy a set of 4 AA NiMH with a charger for the A70 and A80.

I hope I didn't get you more confused about this.

Clément

Link to comment
Share on other sites
Achilles Tang Newbie

Achilles Tang

Posted
  • Author
Posted

Not every shot works as well as the ones posted and I haven't got just one technique that works every time. I'm not qualified to give a tutorial on Photoshop but things I've had success with using Photoshop Elements 1.0 are:

1. Use the Enhance->Colour Cast. Initially I wouldn't use this tool as I thought it would be better to try and use less automated adjustments. However I've found there's nearly always something that should be white in pictures e.g. dead coral, stripes on fish. Click on these and you often get good results. You can always reset and try again if you don't like the result, also by clicking the preview checkbox on and off you can check the results against the original.

2. Create a New Adjustment Layer->Levels and adjust the levels of each colour in turn. I find it's best to leave the red to last and often find that you don't want to move the right hand slider right to the edge of the histogram as the the results often look unnatural.

3. Create a New Adjustment Layer->Hue/Saturation and reduce the saturation of the Cyan. This often removes the cyan cast you get on white objects. You can also try; using the sliders to change the range of colour desaturated; change the hue of cyans to be more blue; increase the saturation of reds and magentas.

4. Create a New Fill Layer->Solid Colour containing red/magenta. Set the layer mode to colour and play with the transparency until you get the colours you want.

You will often need to use more than one of these steps 1 & 2, 2 & 3 or 4 & 3. With practise I find that using 1 & 2 gives me the best results.

When you are ready to display your pictures or print them flatten the layers and use the Sharpen->Unsharp Mark tool to sharpen them up.

Link to comment
Share on other sites
  • 4 years later...
  • 1 month later...
CrystalClear99 Newbie

CrystalClear99

Posted
Posted

Looks like there are lot of expert scuba divers 'round here. I'm a novice diver. been thinking about trying the Cayman islands. What do you think about that? is there any spot you would like to suggest for a beginner like me? what gears can you recommend. I spotted underwater digital cameras on the web but I would like to know the opinions of the experts. I want those best value for money. Anyway, what is the best diving spot near London? do you have a safety guide here in this website?

What do you think about these magazines? http://en.wikipedia.org/wiki/List_of_SCUBA_magazines

worth reading eh?

Link to comment
Share on other sites
  • 4 years later...

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
 Share
Go to topic listing


×
×
  • Create New...