AidanAvery
25-Mar-2024, 09:12
Last night I ordered a packard shutter for my barrel lens. Researching different fashions of mounting the packard shutter, I found a post that described how mounting the shutter on the front of the lens or the back of the lens actually impacts the incoming image differently.
Specifically, if the shutter is placed behind the lens, the image has already been formed while passing through the lens before it reaches the shutter. So, effectively, as the shutter opens and closes it simply reveals the image to the film plane.
On the other hand, if the shutter is placed in front of the lens, it impacts the incoming light prior to the formation of the image. In this case, the shutter acts like a variable aperture that quickly widens and then closes.
This second point kind of blew my mind because, as we all know, different apertures create different optic qualities.
I had been planning on mounting my packard on the front of my barrel lens (it won't fit behind, in any case); however the second point started me wondering about how this might impact the images.
So, a question for those of you with more experience/knowledge of barrel lenses, front-mounting shutters, optics, etc... At the packard's 1/25 speed, will front-mounting the shutter noticeably impact with final image at all? will it change with the depth of field since it is acting as a variable aperture instead of a static, wide-open one? Will it have other effects on the image that I'm not considering? Or, will it open and close so quickly that my final image will still look as if the lens was shot "wide open," at 1/25 shutter speed?
I am particularly curious because my barrel lens is a petzval and I don't want the shutter to reduce its "petzval-y-ness"
EDIT:
Thanks to @reddesert for clarifying with the response below:
It does not matter. The main issue is to make sure that when fully open, the shutter does not vignette your lens.
First, the amount of time that the shutter is opening and closing is a small fraction of the total time.
Second, the shutter either in front of or behind the lens is not exactly the same, optically, as the aperture inside the lens. The aperture inside the lens forms the pupil or aperture stop that governs what rays can pass through the lens. The pupil is maximally out of focus. For optics reasons that are too complex to explain quickly, the shape of the pupil determines the diffraction pattern of the lens, which is why for ex a five bladed aperture will give you a different number of light spikes from a point source, or shapes of out of focus blur (bokeh) compared to a four bladed aperture. However, if you stick a pentagonal hole in front of or behind your lens (like using a vignetter in a matte box), you'll get a pentagonal vignette.
There is a lot of optics misinformation or half-information on the internet, and the idea that the shutter has a different effect depending on whether the lens has formed the image already might fall into that category. What matters is whether the shutter is vignetting the lens. Vignetting can change with front or back placement, depending on lens size and angle of view.
Specifically, if the shutter is placed behind the lens, the image has already been formed while passing through the lens before it reaches the shutter. So, effectively, as the shutter opens and closes it simply reveals the image to the film plane.
On the other hand, if the shutter is placed in front of the lens, it impacts the incoming light prior to the formation of the image. In this case, the shutter acts like a variable aperture that quickly widens and then closes.
This second point kind of blew my mind because, as we all know, different apertures create different optic qualities.
I had been planning on mounting my packard on the front of my barrel lens (it won't fit behind, in any case); however the second point started me wondering about how this might impact the images.
So, a question for those of you with more experience/knowledge of barrel lenses, front-mounting shutters, optics, etc... At the packard's 1/25 speed, will front-mounting the shutter noticeably impact with final image at all? will it change with the depth of field since it is acting as a variable aperture instead of a static, wide-open one? Will it have other effects on the image that I'm not considering? Or, will it open and close so quickly that my final image will still look as if the lens was shot "wide open," at 1/25 shutter speed?
I am particularly curious because my barrel lens is a petzval and I don't want the shutter to reduce its "petzval-y-ness"
EDIT:
Thanks to @reddesert for clarifying with the response below:
It does not matter. The main issue is to make sure that when fully open, the shutter does not vignette your lens.
First, the amount of time that the shutter is opening and closing is a small fraction of the total time.
Second, the shutter either in front of or behind the lens is not exactly the same, optically, as the aperture inside the lens. The aperture inside the lens forms the pupil or aperture stop that governs what rays can pass through the lens. The pupil is maximally out of focus. For optics reasons that are too complex to explain quickly, the shape of the pupil determines the diffraction pattern of the lens, which is why for ex a five bladed aperture will give you a different number of light spikes from a point source, or shapes of out of focus blur (bokeh) compared to a four bladed aperture. However, if you stick a pentagonal hole in front of or behind your lens (like using a vignetter in a matte box), you'll get a pentagonal vignette.
There is a lot of optics misinformation or half-information on the internet, and the idea that the shutter has a different effect depending on whether the lens has formed the image already might fall into that category. What matters is whether the shutter is vignetting the lens. Vignetting can change with front or back placement, depending on lens size and angle of view.