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Old October 29th, 2007, 03:17 AM   #1
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Aperture on 35mm adaptor

On many forums I read that SLR lenses have a crispier image when stopped down a bit. So a 50mm 1.4 lens would "perform" better around 2.8

Now I have always left the aperture of the SLR lenses wide open (1.4 on my nikon 50mm). I just stopped down the aperture on the camera.

So my question is:
Should I close the SLR lens a bit and also the aperture of the camera if needed?

Not sure what the best approach is? I am using a rotating 35mm adaptor like the SGPRO.

Simon Heymans
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Old October 29th, 2007, 07:56 AM   #2
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Close down on the SLR lens when you can. There are a few things going on here that give you an apparently sharper image. First, stopping down deepens the depth of field, making more of the image in-focus and giving the appearance of a sharper image. Also, closing the aperture causes the majority of the light path to pass through the center of the lens, which is typically sharper. Finally, stopping down -- especially outside -- prevents the image on the ground glass from being blown out which is crucial if you want to preserve detail and sharpness in the highlights.
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Old October 29th, 2007, 08:08 AM   #3
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Learn to use Nuetral Density filters. I don't think you want to mess with the aperture on your camcorder after completing the back focusing on your ground glass, imaging element. If you want that beautiful SHALLOW DoF you need the 35mm lens' aperture open as much as possible. The way to deal with too much light and overexposure at that point is with ND filter(s) in front of the 35mm lens. This is especially true for outdoors in the sunlight.
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Old October 29th, 2007, 10:22 AM   #4
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It is abit difficult to close down your lens to F2.8 especially indoors with spinning adapters,with normal lighting, because the light lost of the spinning adapters are no as good as the vibrating adapters like the Brevis or Letus extreme.If you want to use it indoors under normal light and want to set down your lens ,Just use more light .

Last edited by David Chia; October 30th, 2007 at 01:21 AM. Reason: spelling error
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Old October 29th, 2007, 04:36 PM   #5
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It depends on which adapter you are using as a spinning GG. My SGpro tends lose very little light as compared to when I had the LetusFE. Now with the new Extreme I'm sure it is a lot better. Also with the Brevis has proven that it works very well in low light. But not all Spinning GG is worse off than Vibrating GG.
Canon XHA1, SGpro,Flip,FF, RR Mattebox, Nebtek V-R70p-HDA with Canon, Nikkor Primes 24mm f2.8, 28mm f2.8, 35mm f2.0, 50mm f1.4, 85mm f1.4, 105mm f1.8, 135mm f2.0, and 300mm f4.0.
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Old October 29th, 2007, 05:03 PM   #6
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I have the same lens, shooting it both with a DIY spinning adapter, and a Letus35a (Salivating for a Letus Extreme or a Cinevate Flip). Cameras are FX1 and HV20.

Closing down the lense to 2.8 or 4.0 gives the best results, assuming there is enough light. If you go in F8 and up, you start to lose what you got the adapter for in the first place, a limited depth of field. Plus, on some systems where you are just at the edge of the vignette, you start to experience that problem more. Problem is, there is often now enough light indoors, unless you light the place up--- and I am not saying that is a bad thing-- just a fact.

Frankly, the more I have used these adapters, the more I recognize the need to throw adequate light on the subject.
Chris J. Barcellos
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Old October 29th, 2007, 05:06 PM   #7
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That suggestion is a bit global.

A good CD-R sized glass disk of equal groundlgass finish and transmisssiveness to an orbital groundglass, at 1500rpm, is quite capable of outperforming the orbital system up to f11 with f1.8 normal to telephoto lenses and can support higher shutter speeds. The wide-angle lenses offer some challenges. There is of course little point to apertures of f11 beyond proving it can be done as you might as well shoot direct-to-camera.

For the same groundglass texture and otherwise identical optical path, there is no difference in transmissiveness. Disks probably have a bad name because they are nearly always home-made and plastic and because of the early generation disk based Mini35 problem which became known as the vortex from hell, now thankfully a thing of the past.

The CD-R sized groundglass is a bulky and awkard piece to integrate into a kit with rods matteboxes etc., and a very inefficient user of groundglass material, probably about ten perecent of it versus the orbitals which only lose the areas in the circular groundglass not covered by the image frame. It also tends to be more vulnerable to damage as the glass disk is not supported or re-inforced by a frame.

I find indoors under sufficient artificial lighting, all groundglasses seem to be more forgiving of lens defecits relating to artifacts. My guess is that contrasts are not as extreme as outdoors in clear sunlight. It might be a different story with high intensity lighting but that is a luxury many of us cannot afford.

Last edited by Bob Hart; October 29th, 2007 at 05:24 PM. Reason: error
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