aperture and "grain" from the gg

cordvision

cordvision

Well-known member
question: when using an adapter, why does grain become more visible at small apertures. It is logical that you see more grain when using fast shutterspeeds but why does the structure of the gg show up with small apertures?
thanx
Michael
 
which adapter are you speaking of, as my adapter doesnt do this? Spinners for the most part dont do this, Static and vibrating adapters are more alike it seems when it comes to grain. From what I read and from my past experiences with earlier adapters I've owned, static and vibrating adapters show grain at 5.6/f maybe less. The reason it becomes more apparent I'm guessing is because the image on all 35mm lenses gets sharper as you stop down... vs. Shallow DOF=early f:stops or more open lens, generally come with a softer image. Im assuming the softer shallower image has a lot to do with hiding grain on the static/vibrating adapters.
 
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not so much to do with softness, everything to do with Depth of Field (DOF). At larger number apertures the lens resolves everything including foreground elements such as the GG. bwest got it when he said that static/vibrating adapters are more prone to this.
 
I know that vibrating adapters show grain earlier but why does it become more visible with a small aperture. The image is not sharper in general there is just a deeper DOF so I don't see this as the reason for the grain.
Quote:
"At larger number apertures the lens resolves everything including foreground elements such as the GG."
That also seems not to be the reason because the gg is behind the lens and not in front of the lens...
 
This is a mystery to me as well, and a damn good question that somebody should have asked long ago.
Even with spinners I think you see the grain when apertures are small enough.

Lenny Levy
 
I'm assuming that this could be because when the 35 lens is wide open a large swath of light hits the GG perpendicularly "hiding" the gg pits in the grain texture, when we close down the aperture the light source is now coming in from a smaller source near the center of the 35 lens and strikes the focal plane edges at an angle creating shadows from the GG pits. I think grain is more at the edges at this point.

We now "see" the grain due to the "cast shadows" due to a change in light source angle.

GG with Finer texture wont have deep pits so the percieved "no grain". But its there, only that its smaller shadows are cast by the pits even at apertures beyond f5.6 apertures.

Lets imagine a single gg grain as a hill mound located at the edge of the focal plane, at full open its like the sky is so bright with the sun at 12 noon. No shadow. Closing down the lens the sun is at 9am or 3pm, the hill cast a shadow.

Ted
 
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I like Teddybears explanation as this would explain a lot of what I've witnessed with my earlier static type adapters. Even with my current spinner, if I turn the motor off, I get grain as I would with a static adapter. Very useful for critical focusing on the GG... using the grain. Then I flip the motor on and my GG goes spinning "away" as well as the grain. But I think Teddybear nailed it... its the angle the light takes as it hits the GGs pitted surface.
 
That would be the combination of 35mm lens aperture + gg motor speed + cam shutter speed. At some point 1 or two of these in a given situation can "show" the grain. It wont be percievable in certain situations but its still there.

I'd like to share with you some trivia where i got that analogy of a hill as gg grain. You see the main tourist attraction of where i live is this geological wonder called chocolate hills and its tricky to shoot when the light is not right. In my case sometimes i need the shadows to be there! :-)

Ted

1198135479.jpg
 
hmmm, I was thinking about it a little bit more. A small aperture is like a hard light that produces shadows and a large aperture opening is like a soft light which creates soft shadows. So... the spinning adapters just blur out the grain structure (shadows) more than the vibrating one's and this lets us use smaller apertures without seeing the grain structure. The explanation seems logical but I'm somehow still not a 100% sure if this is really the reason for this phenomena since the surface of the gg is very very smooth. Can anybody who actually designs these adapters clarify?
 
This is a mystery to me as well, and a damn good question that somebody should have asked long ago.
Even with spinners I think you see the grain when apertures are small enough.

Lenny Levy
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I shoot at f/16 and f/22 with my SGpro all the time. No grain.
 
marco0782 said:
I shoot at f/16 and f/22 with my SGpro all the time. No grain.
Click to expand...

Just curious, why are you using a shallow DOF adapter if you're shooting at such high apertures? Is it just because you want to keep the adapter on for consistency even in outdoor/high brightness shots? Or something else?
 
it's not just a dof adapter it is a lens adapter. It give you many more options to play with than most stock lenses.
Some people still like deep dof.
 
teddybear said:
That would be the combination of 35mm lens aperture + gg motor speed + cam shutter speed. At some point 1 or two of these in a given situation can "show" the grain. It wont be percievable in certain situations but its still there.

I'd like to share with you some trivia where i got that analogy of a hill as gg grain. You see the main tourist attraction of where i live is this geological wonder called chocolate hills and its tricky to shoot when the light is not right. In my case sometimes i need the shadows to be there! :-)

Ted

1198135479.jpg
Click to expand...

Tedd, looks like you live in pretty country... This is pretty neat...

Around here in LA, we have Vasquez rocks, interesting looking rock formations they use in many movies...
 
Deuceofspades said:
Tedd, looks like you live in pretty country... This is pretty neat...

Around here in LA, we have Vasquez rocks, interesting looking rock formations they use in many movies...
Click to expand...

Thanks Deuceofspades,

Im also fortunate to see the sites for free since im commissioned by my government to do the promotional video for the region. I have the hd100 with DIY adapters as part of my equipment.

Ted
 
Just curious, why are you using a shallow DOF adapter if you're shooting at such high apertures? Is it just because you want to keep the adapter on for consistency even in outdoor/high brightness shots? Or something else?
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I see it as a lens adapter, not a depth of field adapter. Even with deep focus I notice a big difference comparing the optics of a 35mm prime with the HVX stock lens at the same focal length. I want deep focus when I don't want to be as selective about what the viewer's eye gravitates towards in the composition. Other times I might just need to increase the depth of field because I'm filming something very spontaneous and I can't otherwise achieve perfect focus.

As far as outdoor photography, I've done a lot of shooting outdoors using ND filters so I can shoot wide open. A lot of people automatically think f/16 when shooting outdoors, but I say let the style of the film dictate what apertures you use.

it's not just a dof adapter it is a lens adapter. It give you many more options to play with than most stock lenses.
Some people still like deep dof.
Click to expand...

Yeah, basically. I don't lean towards shallow or deep focus. Each project is different. Using vibrating adapters I always felt limited and had to settle for f/5.6 in many situations where what I really wanted was f/8 or f/16.

I still don't understand why companies like Letus and Cinevate keep making vibrating adapters. There is no advantage whatsoever in my opinion. They are only a little bit smaller, but have nowhere near the ability to shoot with small apertures or high shutter speeds. My SGpro is pretty tiny and lets me choose whatever aperture I want which is what any cinematographer needs.
 
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Wait, is the OP talking about closing down the lens on the adapter or the stock lens? Some people seem to referring to the 35mm lens and others to the stock lens. Do both cause grain to show up when closed down?
 
davide

The OP appears to be talking about the attached still lens not the cam lens.

"Do both cause grain to show up when closed down?"

nope. In my tests, closing the stock to a small aperture doesnt affect in the showing up of grain in the image.
I have closed down the stock lens to f16, and no grain.
It is the 35mm (or other types) lens attached to the adapter that causes the GG grain to appear in the image. In some cases like mine it causes the arc pattern of the spinning disk to appear, in the vibrating models, circular patterns are the ones appearing.

What will cause the GG pattern to be obvious from the cam side adjustment is a higher shutter speed.

In this forum, a lot has been said about the sweetspot setting of the stock lens to get a good image in terms of f stop. some say 4-5.6, in my tests, my sharpest edge to edge is achieved at f8 and f11 on the stock lens. f5.6 can achieve good sharpness but the corner most images(outside of tv safe areas) are soft.

This doesnt mean wider opening on the stock lens is not usable, i use even f2.8 on the stock when the corners arent important in the composition, only when it matters do i close down, like say wide establishing shots with lots of detail. Its a creative decision.

As to the fstop of the still(35mm and other types) lens, in my tests i can only go to f5.6 on a 50 mm f1.4 lens before arcs start to appear. on longer lenses the max i can go is f4. Note that these parameters are not the same for the branded adapters with finer ggs. They said they can go up to f16 without seeing grain.

Ted
 
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