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Forum: Pentax SLR Lens Discussion
04-13-2017, 07:51 AM
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Wow! Did I write that? Thanks for the strokes!
Steve
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Forum: Pentax SLR Lens Discussion
04-12-2016, 09:06 AM
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Thanks for filling in the blanks and also for sharing your excellent work with the Zenitar.
Steve
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Forum: Pentax SLR Lens Discussion
04-10-2016, 07:26 PM
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Hmmm...no luck (does not accept messages)...perhaps if I try this technique...are you listening @Dartmoor Dave?
Steve
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Forum: Pentax SLR Lens Discussion
04-10-2016, 07:18 PM
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I will do that. I have tried it both ways on my Zen and was unable to attain adequate sharpness anywhere in the frame without a rear filter attached.
Steve
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Forum: Pentax SLR Lens Discussion
04-10-2016, 10:48 AM
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The back filter is part of the optical path and must be fitted.
That being said, there is a common problem where infinity focus needs to be adjusted. Below are the instructions I posted a few years back to the Zenitar Fisheye group on Flickr:
As with all manual focus ultra-wide angle lenses, fine focus on the Zenitar can be a challenge even for relatively close objects. Everything in the viewfinder is sooooo teeny. You would think that DOF would make it all work, but that is not the case. Magnified live view is your friend as might be a focus screen with split-image focus aide.
Steve
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Forum: Pentax SLR Lens Discussion
04-06-2016, 01:16 PM
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This is quite correct, though a little exaggerated. Probably the best example would be sitting in the IMAX theater where the image is projected onto a hemisphere defining 180 degrees of arc in all directions.
Lacking an IMAX screen, sometimes it is enough to simply add a strong horizontal crop or tilt the frame so that the composition leads the eye to one of the corners where the projection is strongest. It may also depend on the person viewing the photo. I tend to see with a wide rather than long eye when just walking around. Other people tend to have a stronger central focus. If I stop to actively consider my peripheral vision, it is possible to see the leaning trees and curved lines. :eek:
Steve
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Forum: Pentax SLR Lens Discussion
04-06-2016, 09:25 AM
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To be more serious, there is more to shooting with a fisheye than "fisheye effect". While many may buy one as a novelty lens, I use mine (both the Zenitar and Rokinon) as special purpose wide-angle lenses with specific optical characteristics that work well with many subjects.
The bending of lines is not barrel distortion. It is a design characteristic. "Fisheye" is the common name applied to a family of lens designs that use some form of circular projection. Most camera lenses use rectilinear projection (straight and parallel lines appear geometrically true). Those straight lines come with a price when applied to wide and ultra-wide angle lenses. The price is something called "volume anamorphosis" where objects assume unnatural, odd, or distorted shapes. While present through most of the field, this effect is most obvious towards the periphery.
Translation? A rectilinear projection is not consistently true for all aspects of geometry.
A good parallel might be the Mercator projection used for maps where places such as Greenland appear to be disproportionately huge. By using a circular projection, this distortion is largely avoided, though at the cost of non-straight lines in some orientations. What does this mean to the photographer? Consider a small set of talking points:- The human vision is not rectilinear
- The field of human vision is not flat
- IMAX lenses are not rectilinear
- Much of what is termed "fisheye effect" is simply perspective resulting from the wide FOV. That is why a cropped fisheye image appear less "fishy".
- Straight/parallel lines are very rare in nature. Archeologists leverage this fact when doing aerial or satellite image surveys in search of ancient ruins/cities.
- As long as the horizon appears straight and level, landscape photos taken with a fisheye lens appear quite natural to most viewers
- Fisheye line bending depends heavily on the line's orientation to the lens axis
- In cases where the horizon and other lines appear bent, the scene may still appear quite natural to most viewers, if perhaps a bit disorienting
- For subjects where critical portions "wrap" the viewer, a circular (fisheye) projection will provide a more realistic representation to the viewer
It is that last feature that drives most of my fisheye shooting. Despite the obvious novelty aspect of shooting with the Rokinon 8mm on APS-C, I seldom use the lens in that way. I have used both it and the Zenitar for general landscape photography and for events (wedding receptions are an obvious) and other settings where tightness is a characteristic of the scene. While I have several excellent means to "de-fish" in PP, I seldom do so.
Back to whether a fisheye designed for FF is useful, on APS-C, I would give it a qualified yes. I can and have shot "fishy" with the Zenitar on my crop format cameras. I can and have shot "straight" with both the Zenitar and the Rokinon on APS-C. I have also shot "straight" with the Zenitar on FF 35mm film.
Zenitar 16mm on K10D...most viewers never notice the curve...If the lens axis is level to the earth, the horizon will always be straight, but I was not concentrating on the lens axis...
This Zenitar shot on K10D is very fishy, though you would be hard-put to notice if you had not done the shot.
Rokinon 8mm at my daughter's wedding reception...no alien heads in this scene...
When I show people that last one, they are always surprised when I mention it was shot with a "novelty fisheye" lens. ;)
Steve
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Forum: Pentax SLR Lens Discussion
04-06-2016, 08:17 AM
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Damn! All this time and I thought I was doing good work with my Zen on APS-C as well as 35mm film. Now I know that my tool is worse than useless. I am so discouraged :(
Steve
(..."only 180 degree" on FF?...I thought that was the traditional fisheye FOV, though I have been wrong before...)
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Forum: Pentax SLR Lens Discussion
04-05-2016, 09:54 PM
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I was wrong...the photo below is on my Flickr stream, but is a crop:
I did a little look-see in my archives and found another that better shows what the lens is capable of on the K-3. I will PM you a link to a full resolution version of the crop.
Steve
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Forum: Pentax SLR Lens Discussion
04-05-2016, 09:02 PM
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Mine does very well, though I don't have any on my Flickr stream for the combination. Let me see what I can find on my hard drive.
Steve
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