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05-10-2016, 10:35 AM   #1
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Leaf shutter "look"

I've been experimenting with my new eBay acquisitions and I get a feeling that when I shoot using the leaf shutter, the photos look different to when I use the Focal Plane shutter. I can't identify what is different, perhaps a bit sharper, a bit more contrastier, slightly different bokeh?

Are there any proven physics behind a leaf shutter rendering slightly differently to a focal plane shutter? Or is there such a thing as a 'leaf shutter look' (in a similar fashon to a 'Zeiss look' or a 'Medium Formal look')? Or maybe I'm just imagining it

Regardless, really enjoying using the 75, 90 and 165 LS lenses on my 645z.

05-10-2016, 10:55 AM   #2
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They do render motion blur differently:


QuoteOriginally posted by glass Quote
I've been experimenting with my new eBay acquisitions and I get a feeling that when I shoot using the leaf shutter, the photos look different to when I use the Focal Plane shutter. I can't identify what is different, perhaps a bit sharper, a bit more contrastier, slightly different bokeh?

Are there any proven physics behind a leaf shutter rendering slightly differently to a focal plane shutter? Or is there such a thing as a 'leaf shutter look' (in a similar fashon to a 'Zeiss look' or a 'Medium Formal look')? Or maybe I'm just imagining it

Regardless, really enjoying using the 75, 90 and 165 LS lenses on my 645z.
05-10-2016, 11:34 AM   #3
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For static objects, I can only imagine that the leaf shutter at its higher speeds acts like an opening/closing iris, transitioning through apertures while opening and closing and thus overlaying exposures with a little more depth of field in the process. That could influence the look of the out of focus area.
05-10-2016, 12:44 PM   #4
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QuoteOriginally posted by JensE Quote
For static objects, I can only imagine that the leaf shutter at its higher speeds acts like an opening/closing iris, transitioning through apertures while opening and closing and thus overlaying exposures with a little more depth of field in the process. That could influence the look of the out of focus area.
Intriguing. I like it.

05-10-2016, 12:56 PM   #5
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Interesting proposition. Might be somewhat complicated by the fact that the leaf shutter blades tend to close in a star pattern rather than evenly like your typical aperture diaphragm:



So even at any point in the shutter actuation when you are closed down at any particular absolute f value in terms of the area of the opening, there is still an influence from the incident light at different angles entering from the arms of the stars that wouldn't come into play with a round or quasi-round iris opening. Also at any one given moment to the next, there is a swirling effect, since the "tips" of the arms move in clockwise and counterclockwise directions with respect to the vertical/horiontal axes as the shutter goes through its range of motion.

Even further complicating things is that if the iris is wide open, this swirling effect would presumably go out to the edge, while iif the iris is closed further, it would only really affect the center of the image, since the tips of the arms are blocked through more and more of the exposure as the iris closes
05-10-2016, 01:06 PM   #6
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QuoteOriginally posted by dcshooter Quote
it would only really affect the center of the image
Similar to the iris, actually next to it, the leaf shutter is positioned where it almost equally effects all parts of the image (ideally 'infinitely defocused').

The opening/closing impact hypothesis could easily be tested by shooting a series of pictures at constant aperture but with varying shutter speed (and sensitivity), starting from the shortest time. The difference to the focal plane shutter rendering should then disappear quickly with longer exposure times, and as dcshooter pointed out should be most visible at fully open aperture.
05-10-2016, 01:46 PM   #7
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QuoteOriginally posted by JensE Quote
For static objects, I can only imagine that the leaf shutter at its higher speeds acts like an opening/closing iris, transitioning through apertures while opening and closing and thus overlaying exposures with a little more depth of field in the process. That could influence the look of the out of focus area.
There are a few users on this site who have hypothesized that leaf-shutter blades act as a secondary iris in a manner similar to those in specialized "Smooth Transition Focus" (STS) lenses from Sony and Laowa. I have trouble visualizing how this might work since an "iris effect" at any particular diameter would be very short-lived in terms of its contribution to the image.


Steve
05-10-2016, 02:12 PM   #8
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Would we not see a similar effect by perhaps using an ND filter (to increase exposure time to something usable) and then manually stopping down the aperture during the exposure.....a confused region outside the DoF region in which blurr and sharp are overlaid.

Perhaps I'm thinking this too obliquely.

Bob

05-20-2016, 04:55 AM   #9
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Thanks for all your responses. I did some testing and there is a distinct difference in bokeh between LS and FP. As mentioned above, this is most noticeable at 1/500 wide open, and the effect diminishes at slower speeds and at smaller apertures. The LS bokeh is so much smoother, almost more like a gaussian blur effect, whereas the FP bokeh is more choppy with 'doubling' of visible elements, especially straight lines. This makes the objects in the LS bokeh remain intelligible, whereas the FP blur can be quite confusing to make out what the objects are.

The sharpness difference is down to camera movement. Without paying careful attention to technique (e.g. heavy weighted tripod and mirror lock-up), many FP shots have a tiny amount of motion blur (even at 1/500) whereas almost all of my LS shots are tack sharp, even hand held at 1/500. As my shooting technique is the same between LS and FP, I guess the extra blur is due to mirror slap.
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