One of the key functions of Wetpixel is to provide underwater photographers with a forum to exchange ideas, encouragement and information. What continually draws me back is the chance to learn about the new underwater photographic techniques that are possible with our new digital cameras. These are not techniques that you can read about in books. They are being developed here and now, on a daily basis, by members of this website. One such technique is available light photography using filters.

Of course, underwater filter photography is not new. I know photographers who were using filters underwater back in the 60s. But the problem that they all had was that it was nigh on impossible to get a filter that exactly counter-balanced the filtering effect of seawater (which varies both with depth and what’s in the water). As a result the colours recorded on film with filter shots were never quite right, and ultimately disappointing. Strobes seemed a much better solution for colourful underwater images.

Underwater videographers found things very different. Filters worked perfectly for them because their cameras had adjustable white balance, which could be used to fine tune colours and produce excellent results. This fine-tuning is now available to the still photographer because digital cameras also have adjustable white balance. And as a result filters have finally become a mainstream technique for stills.

The UR Pro SW-CY

UR Pro’s Colour Correction filters have long been favourites of videographers. A quote from Stan Waterman on the UR Pro website sums it up for me: “URPRO filters provided dependable color balance to an otherwise monochromatic blue world…I depend on them”. If they are good enough for Stan, then I reckon they are worth a try! I am a big fan of their CY filter, designed for clear, tropical water and when I was asked to try their new product the shallow water CY filter (SW-CY) back in January I leapt at the chance. This product is due to be released in June (2005).

UR Pro’s justification for the SW-CY is to provide a filter suited to work between the surface at 8m (25ft), the standard CY filter is designed for an overlapping but deeper range of 3-20m (10-60ft). The two filters look identical, but have quite distinct filtration characteristics.

Most still photographers find that the most pleasing filtered images come from shallow depths (

10m/30ft), although filters improve significantly on reality, the shots can still look a bit drab. Furthermore filters work by subtraction of light so at depth we are forced to use higher ISOs to compensate for the ever-decreasing illumination, which introduces noise. Videographers can get away with these compromises because movement enlivens their images, but drab colours in a still image just leave the viewer wishing for flash! The new SW-CY promises to be well suited to the favoured filtration depth range of the still photographer.

Testing the filter

For thoroughness (and because I didn’t have a camera of my own back in January!) I decided to test the SW-CY filter on the two camera systems I had borrowed. First I did the fully automatic evaluation using an Olympus 5060 with an INON WAL using AUTO white balance and shooting JPGs. Then for those who like more control I tested it on a Nikon D70 with a 20mm lens shooting in RAW and custom white balancing using the dropper in Photoshop’s Camera RAW Plug-in. On the same dive (I did a lot of popping back to the boat) I shot the D70 with a CC40 Red filter (on the 10.5mm lens) and a standard UR Pro CY filter on a 17-35mm lens. All these shots were taken in 3.5m (14ft) of water near Stingray City Sandbar.

The SW-CY worked very well on the Olympus 5060 and nearly all of the images looked fantastic straight from the camera. The colours of sand, stingrays and skin tones were all very pleasing. Human skin tones are notoriously tricky to get right but I thought that they were recorded with impressive accuracy. In short with the SW-CY the 5060 produced great colour with auto everything, point and shoot simplicity.

Unsurprisingly, the SW-CY also yielded excellent results with the D70 again producing accurate skin tones and natural environmental colours. I tested the filter against a standard CY and a 40CC Red filter and, after custom white balancing, all three produced excellent results. The SW-CY required the smallest white balance correction of the three relative to a “standard” daylight, but none required large white balance corrections. These corrections were small enough not to have a detectable effect on image quality (large white balance adjustments in RAW do degrade image quality).

One point of interest is that the camera’s AUTO white balance produced more pleasing colours straight from the camera with both the UR Pro filters than the 40CC Red. It is possible that the Colour Correcting (warming) UR Pro filters make it easier for the camera to AUTO white balance than the Colour Compensating (adding red) 40CC Red Gel?

On the negative side, my only frustration with the UR Pro filters is that these glass sandwich filters can only be fitted to lenses that accept screw filters. This notably excludes my two main wide angle lenses: the 10.5mm and 16mm fisheyes.

Conclusion

The SW-CY is excellent and works well (as is clear from the images). I would expect most photographers would not want to buy both the CY and SW-CY given the large overlap in their operational depth ranges. Which filter to choose depends on what, where and why you shoot. If you want a versatile filter to use while diving then the standard CY is still your best choice. However if your reason for getting in the water is photography, and you are prepared to constrain your diving within the depth range of the filter, then the SW-CY used in the brighter light of the shallows is an excellent choice.