Question about leaf shutter(?) showing up in out of focus highlights

(just to state the obvious, those are detail scans from two different shots)

It's the image of your iris diaphragm.

Sorry, my bad, ignorant post without looking at both sides of the image! I thought you were talking about the pentagons on the left. Don't know about the pinwheels.

Wierd, don't think I've ever seen the like. Maybe, if the lights are blinking, if it blinks on just as the shutter is closing or something it might cause just that effect ?

Brad, do you remember what kind of lights you captured that have the pin wheel effect? I suspect they were animated signage. The kind one would see en-mass in Las Vegas or Atlantic City. They are typically banks of LED or incandescent lamps that are computer controlled to create the illusion of movement. They are turned on and off very quickly and what one perceives may be a blooming flower or exploding firecrackers etc.

I believe you have captured the animated sign mid-cycle. You can see a similar effect if you take a picture of a television with a shutter speed higher than 1/60th (60hz).

Thomas may be right, but three separate animated signage lights to be exactly in phase (see the positions of the spokes - they are identical) is unlikely. This is more likely caused by slow shutter blades than anything else. Usually the time of the actual blade opening and closing is much smaller than the open interval (except at the fastest speed).

Lets try to compute this. If we assume that at the fastest speed - 1/500, the shutter essentially just opens and closes we get an opening time of 1/1000 sec and closing of 1/1000 sec; i.e., 1 ms for either. At 1/125 sec, we have a total shutter open time of 8 ms; of this the opening time is 1 ms and the closing time is 1 ms; the shutter is supposed to stay open for 6 ms.

Chances are, your shutter has slowed down, such that the opening and closing time is significant compared to the total open time. This would cause what you are seeing.

So if you want to validate (or invalidate) this hypothesis, run a few tests: see if this happens with other lenses as well; see if shutter speeds are accurate by doing a constant EV test (take pictures at different aperture/shutter speed combinations keeping the same EV) and post back.

Thanks for the responses... In hindsight, I think that the slow shutter hypothesis is less likely than the blinking light one (it is, after all, times square) for the following reason-

1) The image of the blades seems pretty crisp, much as a flashgun will freeze action. If the blades were simply slowing down, the image would be overall darker, but unless they slowed in an exceptionally uneven matter (stopping for a moment at one position, then continuing on) they shouldn't leave such a specific and hard-edged profile... also, my exposure times for the lens seem pretty much right on for my meter, whereas I would think I would keep underexposing images at 1/125- 1/250 1/500 if I had a sticky shutter...?

There being a number of bulbs in sync seems actually reasonable, given that much of the signage out there is flashing in some sort of synch, and the lights seem similar enough in hue and placement for me to think they're part of the same sign.

Also, and perhaps more tellingly, there are other highlights that don't seem to have the same problem, leading me to think (upon reflection) that it isn't an overall lens issue- If it were, wouldn't other specular highlights exhibit the same thing?

Because of this, and because the lights typically seem pretty dim compared to ambient (implying that they were only on for part of the exposure), I'm going to hesitantly throw my weight behind the "the light blinked off right at the beginning of the exposure or blinked on right at the end" hypothesis.

Sounds like I'll have try the constant EV test next time I have some extra roll in my camera...

I do think it is the shutter showing.
The speeds used are short enough for the shutter blades to be in the aperture for a considerable protion of the exposure (No need for the shutter to be sticky to produce this, i think).
Just like the aperture's outer shape determines the shape of the highlights, the star shaped aperture, created by the shutter blades, inside the aperture formed by the diaphragm determines the shape of the diffraction pattern that shows up in these out of focus bits.

By the way: the shutter shaped image is not really crisp. We're seeing a distribution of light: more where the first thin star is created by the shutter opening, less where shutterblades keep blockingthe aperture longest.

Brad, do you have any more images that show this? Your flashing light hypothesis is also certainly possible. What I'm trying to get at is that if you can find an image which shows this effect on some highlights but not others (within the same image) then you rule the shutter out, and the flashing hypothesis wins.

Vijay,

Not necessarily. In fact, i think that it is not either or, but a combination.
The shutter being caught in the 'star-phase' by a flashing light will lead to a highlight-blob showing the shutter pattern inside the outline of the aperture. Other light sources burn long enough to 'drown' the shutter/star pattern, and produce the blobs without distinct pattern, only the outline of the aperture.
So it could be (and i tink it very likely) both the shutter and flashing lights.

Q.G. - yes I suppose that's possible too. So I guess Brad should do a constant EV test anyway with slide film, right?

it happened to me some years ago. If I recall correctly it happened taking pictures of water reflection so the "blinking hypothesys" could have some sense. At the moment I don't have in my hand the picures but if you come back to visist this thread in some weeks I'll post the pictures, may be with more details (lens, aperture, speed, etc.), so may be we'll discover this mistery.