Archive for July, 2010
The new digital revolution has added problems for the photographic community. Digital offers many features on the fly that film cameras cannot. Film cameras have one great advantage for the underwater photographer, the ability to take wide-angle images. We commonly use 14mm, 15mm, 18mm, 20mm and 24mm wide lenses with our 35mm film cameras. Using wide-angle lenses is paramount to underwater photography. We use it to get close to large subjects to maintain saturated color and perspective.
Unfortunately, digital cameras have a problem supporting very wide lenses, especially for cameras that use interchangeable lenses. A lens with a wide angle of view has to be factored to fit the size of the smaller digital chip. The CCD and CMOS chips are smaller than the traditional a 35mm film area. This factoring will convert a standard 28mm lens convert into a 42mm lens. Nikon developed a 12-24 zoom lens that most of us looked forward to as an answer for some of the wide-angle issues. Using the12mm setting and a D100 seemed to solve some of the wide-angle issues by giving us an effective focal length of 18mm. This is a respectable focal length.
We were elated when we got the first lens to test. Al Bruton grabbed the lens along with his Subal D100 housing, a SWB dome port and a 30mm-extension ring. He went to the pool to shoot his test chart. It was a disaster. The lens wouldn’t focus close enough and the image suffered from pincushion with a +4 diopter on it.
In an attempt to correct this Al added a + 3 diopter to the lens to make it focus closer behind the SWB dome. This is all we had to test at the time and it was disappointing. Later we obtained a bigger dome that the SWB and the lens worked better with. (Sorry, I don’t have the images to show you at this time). There are quite a few photographers getting great images with this lens now that the domes are available to meet the demand by the lens.
The pincushion was worse, but the edge sharpness was better. Without having the right dome set-up Al could not get satisfactory results. He continued to test several options with different extension rings and diopters, but the best was the 30mm extension ring and +3 diopter. With a +3 diopter Al was able to focus to 3″ inches in front of the dome. When we tested the lens above water with the +3 diopter we discovered that the pincushion was just as severe. The Nikon lens design set the wide-angle image to compensate for the chip size and made a lens with the nodal point set far forward from a standard lens.
The result is that any glass filters added to the lens caused optical distortion. This included the addition of a glass dome port to some extent. If you put the 12-24 behind a flat port you will not have an effective 18mm lens but a 24mm lens due to the refraction index of water and a flat port. Al has decided that this lens is not good for underwater use and will continue to use it for topside photography where it performs very well. If he is going to use this lens underwater, he will have to fork out some money for a bigger dome that helps place the lens in the right nodal point and the need for the diopter will be unnecessary. The problem for acceptable wide-angle lens use underwater is still haunting photographers. However, the future is getting brighter. Jim Hellemn is using the Nexus D70 housing with a 40mm extension and the 170 dome for the 12-24 lens to shoot his underwater panoramas where he has to over lap the exposures and stitch them together with software. The best optical setting was found to be at the 17mm focal length for his use.
|4″dome with 15mm Sigma lens||WP7 dome with Sigma 15mm lens|
|12-24 Zoom /Subal SWB +30mm extension, +3 diopter||In an attempt to correct this Al added a + 3 diopter to the lens to make it focus closer behind the SWB dome.|
|Jim Hellemn testing the 12-24 in a Nexus D70||Sigma 15- aread covered at the closest focus was 5″ inches wide.|
Meanwhile, Nexus sent me their new special 4″ inch port for the Sigma 15mm fish eye lens to test with their D100 housing. Like the Nikon 16mm, the Sigma has the 180-degree angle of view. These lenses have a barrel distortion in the design and do not keep a linear line straight. The chip factor of the D100 reduces these lenses from 180 degrees of coverage to 120 degrees. The Sigma lens will focus down to 5.4 inches in front of the lens and the Nikon will focus to 10.5 inches. Nexus chose the Sigma lens over the Nikon because it will focus closer and diopters cannot be added to the front of these lenses.
The 4″ dome created a wider view of about 8 degrees over the 7″ dome.
Notice that there is some barrel distortion, but the target on the side of the pool is actually curved because it is resting at an angle on the side of the pool.
The 15mm in the WP7 was at 48″ from the target to get full coverage. The 15mm in the 4″ dome was at 39″ from the target to get the same coverage. The angle of view is wider but the barrel distortion is more. Minimum focus in the front of the small dome is 3″ inches and 5″ inches with the WP7. Nikon’s 16mm lens could only focus to 9 inches.
The area covered at the closest focus was 5″ inches wide.
Conclusion: Wide-angle photography is still a problem for the digital cameras that use standard 35mm lenses. The only camera that won’t have this problem is the Canon 1Ds and Kodak 14n. They have full frame 35mm sensors and the standard wide angle lenses work fine with these cameras. They are very expensive and there are few housings that support these cameras. SeaCam and Sea & Sea have introduced housings for these cameras. The cost for a camera, port, lens, and housing is about $18,000.00. A D100 housing and camera and port will cost about $4,600.00.
Is it worth it to have the standard wide-angle capability? We have shown that the cameras with the smaller chip area have difficulty providing good wide-angle coverage without some lens distortion. The 12-24 is a compromise with pincushion distortion unless you use a larger dome and have it set at the critical nodal point. The 15mm and 16mm lenses will give 120 degree coverage with some barrel distortion. Software like PanoTools has the ability to straighten out the curvature in the images in a post production computer process so you will have perceptively corrected images in the final out put. It seems that cost is the biggest hurdle to get wide angle with digital cameras. The alternative is less costly and with postproduction software you will have good wide-angle images.
Nikon has announced that they are making a 10.5mm fisheye lens for their D100 camera. We just tested this lens in the Nexus housing for the D70 and it works very well. The 15mm Sigma and Nikon 16mm do a fine job at 120-degree angle of view. The 10.5mm fisheye is a true 180-degree wide lens for the D100 and D70.
A lot of us are making the jump into digital photography. We are also keeping our 35mm systems so we have alternative wide-angle capability. Soon there will be a single system that does it all. It may be a few more years before this is cost effective and available to us.
Al Bruton opted not to use his 12-24, but a lot of others are having success with it. Sigma has their 12-24 out now but I have yet to test it. Maybe it will work for my Canon Rebel Digital. So far I like the results with the Sigma 15 in the Nexus dome. The Nikon 10.5 for the fish eye and the 12-24 works for me in the bigger domes. I hope Canon starts to offer lenses like the 12-24 and 10.5 since I am a Canon system user. I have the Canon 1Ds with full frame coverage, but the housings is a beast. After shooting with the Rebel Digital and the Nikon D100 and D70 in different housings I can say that the D70 in a small housing is much better to use underwater.
One of the most frustrating experiences you can have when you arrive at your destination is not understanding how your camera works or not having all the parts you need to make it work. I hope the following information will help you avoid that experience. Most of this is common sense but we all get in a big rush to go on vacation forgetting the little things that we all need to pay attention to. Don’t get stuck spending your vacation time trying to figure out how to get your pictures to come out better or how to make the equipment fit together and function. By following the suggestions below you should be better prepared than most and ready to take great pictures.
1. Set aside time to read…read, and re-read your camera manual. Get to know your camera and its functions so you can operate it in the dark.
2. Write down important notes that will cover the features you think you’ll be using the most underwater, such as: the best mode settings, color balance, file sizes and flash settings. Remember that your camera has a lot of built-in functions that you probably won’t use. The phrase, “Keep it simple” applies to this process. And performing complicated operations underwater while you are somewhat under the mental nitrogen fog can be even more complicated.
3. You must practice…practice…practice. Make sure you know how to load the camera into the underwater case, install fresh batteries and media cards, clean O-rings and know other functions needed to operate while in the dark. You should be familiar with the assembly and function of your accessories like the camera tray, strobe arms and strobe sync connectors.
4. There is something to this suggestion of working in the dark. You can simulate the underwater experience by testing your camera and flash system in your home during the evening where you can lower the light levels to equate the underwater environment. With your pen in hand and a tablet of paper to record your operations, you can begin to use your camera and discover what operations work best for you and which settings provide the best pictures. Aperture at f8 for best depth of focus is a good start for close-up work in the range of 3 inches to 18 inches. Use the manual mode setting on the camera for the close-up work. Set the Shutter speed to 1/125th to help reduce any ambient light that might effect the exposure.
5. Set up some test objects on a table and take pictures of them at different distances. Start at close–up range (as close as your camera will focus) and work out around 4 to 5 feet away, which are the usual working distances underwater. Test your auto focus at very low ambient light. Most small digital cameras do not have manual focus but if they do, it is a problem to use it effectively. Nighttime photography will require an external focusing light. This will also help during the daytime when subjects are in caves or under ledges where the available light is too low for the camera to focus. Turn all the lights off and use one low wattage bulb as far across the room as possible to see if your camera will auto-focus on the subject under low light conditions. Test your external strobe and record notes about the correct exposure for different distances. (Your test subjects should have a wide range of colors and brightness, full black to solid white). The more you test on land now the easier it will be to operate your camera underwater later provided you re-read your notes on the plane.
6. Make a travel checklist of all the items you’ll need for your photography.
a. Camera: Media cards with enough storage to retain 200 images at full resolution. Remember to take your instruction book with you.
b. Batteries: all sizes that your equipment requires and spare batteries and chargers to match with foreign plug adapters. Make sure your charger will operate on both 110 and 200 voltages.
c. Housing: Spare main O-rings and the correct lube for them (using the wrong kind of O-ring lube could damage the O-ring resulting in a flooded camera). Dry silicone dehydrator to prevent your housing from fogging up on the dive, and lint free drying cloth and lens cleaning cloth.
d. Strobe: If you are using an external strobe make sure you have the correct batteries, sync cables, strobe arm, attachments and trays and handles for your system. One short extension cord, 12 inches long, with 3 multiple outlets incase you run into only one electrical outlet and you need to charge all your equipment at once.
e. A travel case with enough room for all your equipment but not too large so you can’t fit in the passenger area as a carry-on. Some short local flights will not allow very large carry-on bags.
f. Additional lenses: Macro or wide angle and some way to store them underwater when you are not using them.
g. Name labels on all cameras, housings and assembly, and chargers so your equipment doesn’t get mixed up with someone else’s.
h. Your passport plus a copy of your passport. A list of all your cameras and lenses, etc. with serial numbers for customs documentation.
i. A laptop computer or portable storage hard drive that will allow you to back up media cards on location and chargers or spare batteries for these units.
7. Take extra time to do this entire list and prepare your equipment in advance and then enjoy your trip.
8. When you return from your trip thoroughly clean and properly store all your equipment in a dry case or storage area.
9. Enjoy all of your fine images.
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