So I'm wondering if this has to be combined with other optical defects to make it easier to come across. I am aware of this effect, but I'm not sure if it accounts for all the swirl you can get, because some lenses seem more prone to produce swirl than others. It's a consequence of the clipped shape of the light paths at oblique angles through the lens. It should be readily apparent from this how an oblong aperture (at oblique angles) would create the "swirls" towards the edge of the frame. One of my little experiments illustrates how the shape of the aperture impacts the bokeh: As you tilt the lens, the spot of light streaming through the lens is clipped on one side by one edge of the front element and on the opposite side by the opposite edge of the rear element.Īnyway, if you have an image with a more complicated OOF background than the simple point sources in my photo, the blurred pattern will form the "swirls" at the edge. ![]() Hold up your unmounted lens, and rotate it through different angles while you observe the light pattern through it, and you will see the same shapes. Note that the OOF lights in the background have a circular bokeh pattern towards the center of the frame and a clipped, oblong bokeh pattern towards the edge. Consider this photo, taken with a 100/2 at f/2.0 on a 5D: Īnyway, as far as I understand, it's called spherical aberration, but I might be off. I happen to like it in the background blur sometimes, and like these older lenses I have for "defects" such as these - they add a bit of flavour rather than the clinical edge-to-edge sharpness (though it makes the lenses a bit less predictable too - not always an advantage). ![]() Both lenses are not corrected all too well wide open, which under conditions can lead to this different, slightly nervous OoF rendering. I'm not optics expert (there are some around, I hope they chime in), but I sometimes do see a similar effect with my Nikon 50mm f/1.2, and to a lesser extend 35 f/1.4 (old manual focus lens - not the current model). Given that both your bodies are full-frame, it is hard to explain why on one body it would show, and on the other not. And another discussion here.Īwful or not is a matter of personal preference, but in the foreground, it is quite distracting in the background a lot less so to me. There may be a Lensbaby doodad designed with a smaller image circle to emulate that effect on smaller sensor digital cameras.Īlso, other owners of the Canon 50/1.2 have observed the same effect. But the effect is often minimal unless used on a large format camera. Some photographers still like the effect and have adapted Petzvals to their cameras. It was considered a desirable effect in that era. ![]() ![]() The effect is similar, but not identical, to the older lenses like the Petzval, which tended to emphasize the swirls at or near infinity, rather than at close range as you're seeing with your lenses. The lenses were designed for a larger format where the effect would show at the periphery. Same problem I have with my special effect and soft focus lenses on cropped sensor digital cameras. If you haven't seen it before on your 6D: you may not have been close enough to the ground or didn't include enough out-of-focus foreground in the photo or weren't shooting wide open.Īnd if you didn't see it with APS sensor cameras it's because most of the effect is cropped out. Shoot exactly the same scenes with any Canon full frame dSLR (or 35mm film SLR) and you'll see the same effect. It's not uncommon, especially with fast lenses wide open.
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