Defishing Nikons 10.5mm fisheye lens?

As many of you know one of the interesting lenses I shoot with is the Nikon 10.5mm f2.8 DX fisheye lens. This lens covers a lot of territory with a 180 degree corner to corner diagonal view giving you a full frame but somewhat distorted image. I don’t use the lens regularly but the odd scene comes up where the 180 degree field of view is exactly what’s required. From my experience, if fisheyes are used carefully this distortion often isn’t even very noticeable. This distortion is of course what many photographers are looking for but personally I really don’t like the “fisheye” feeling.

A few different techniques can be use, both while shooting the image and later if required in post processing. Certainly avoiding straight lines near the edges of the image can help as straight edges take on a very pronounced curve. Other subjects that tend to work well are more organic shapes without straight lines.

Take the three images below for examples. In the case of the rowers, keeping the horizon in the middle of the image creates a straight horizon. A badly curved horizon doesn’t feel good to me so by centering the horizon we tend to minimize this distortion. While this method of shooting can lead to somewhat static images, a little cropping from the top could eliminate the centered horizon. The second photo of a beaver tail cactus highlights the idea that if you don’t have many straight lines often the heavy fisheye distortion is visually minimized. Some images don’t really have the “full fisheye” feel although on close inspection many of the elements are there; curved lines and horizons, strange distortion. The third image of the music crowd definitely is very wide but for some unknown reason still works for me.

Rowers photographed with the Nikon 10.5mm Fisheye lens

Rowers photographed with the Nikon 10.5mm Fisheye lens - keeping the horizon centered prevents curvature

Beaver tail cactus in Joshua Tree National Park

Beaver tail cactus in Joshua Tree National Park, no straight lines in this fisheye photograph

Fisheye view of the crowd at the Islands Folk Festival

Fisheye view of the crowd at the Islands Folk Festival

For images that “don’t work” another option is to shoot with these fisheye lenses and use software to correct the apparent distortion.

In the case of the wooden boats at dusk shot at the wonderful Port Townsend Wooden Boat Festival, the first image shows the type of distortion that can be expected with the Nikon 10.5mm fisheye when straight lines are placed near the edges of the frame. Do I like this look? I’m not sure personally. I think in some cases it might not matter but at the same time, this isn’t the way I “saw” the view so the photograph doesn’t really portray my vision.

This is where the defishing tools come in. These software tools allow you to straighten the curved lines and in effect remove the heavy distortion that comes with these lenses. I’ve been using the Nikon NX2 software to defish primarily because this is the software that I convert my RAW files with but Adobe PhotoShop and countless others have defishing software available. Does it work? All I can say is that it changes the image both in the visual interpretation and the quality.

In the two images below I certainly prefer the defished photograph but this does come at a price. The Nikon 10.5mm f2.8 is a very sharp lens and a large print of the top image would be relatively sharp even in the corners. When we defish we are changing the shape of the image dramatically with pixels in the corner being interpolated to fill in the area. Let’s take a look.

Wooden boats shot with the Nikon 10.5mm lens

Wooden boats shot with the Nikon 10.5mm lens

Wooden boats shot with the Nikon 10.5mm lens, image defished with Nikon NX2 software

Wooden boats shot with the Nikon 10.5mm lens, image defished with Nikon NX2 software

Let’s take a look at 100% crops from the lower right corner of both images. Something to keep in mind for the scientific crowd and pixel peepers, these images were shot in a real photography situation like so many that I encounter, not a fancy test setup that I don’t really have time for. The exposure time is 1/5 second at f5.6 at ISO 500 with my Nikon D300 mounted on a tripod… high up on a docked boat. These photos have no sharpening performed on them either in camera or during post processing. As I have said, real world here. In a perfect world my tripod would be on solid ground and I likely would be working with an aperture of f8 or f11 for optimal sharpness.

Certainly the defished image holds up very well. If we were to view the full photograph these would be somewhere in the 40 inch wide range if printed, in other words a very large print. Once we defish the image there is definitely a loss of corner sharpness but again, let’s be fair. Even if we were to make a print 40 inches wide the apparent sharpness would be quite good as the viewing distance would also be large. I might consider sharpening the photos slightly as well although with the higher ISO used it might accentuate the “grain” and noise a little. Reality; for the type of work I do (magazines and books) I would not hesitate sending either of these images out to a publisher, they both would look stunning as a two page spread.

100% crop of fisheye image - normal

100% crop of fisheye image - normal

100% crop of fisheye image - defished

100% crop of fisheye image - defished

What’s my verdict? I have found the Nikon 10.5 mm fisheye to be a very valuable tool to work with and have started using defishing software when required. I’m finding that this is a logical post processing step for many of the photographs shot with the Nikon 10.5mm lens, bringing back more of my “vision” than what the raw image showed. Pixel peepers may not be overly happy but most of us live in the real world and the quality lives up to any if the requirements that I and my publishers have.

Any comments or images to share?

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