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Old March 23rd, 2009, 10:53 AM   #1
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"Rotate Stuff" inside the 35mm adapter?!

Hi, i actually trying to DIY the 35mm adapter..but in the stage of very beginning...

2 question:~

a) Focusing Screen (GG). s'ld i buy for better result? i saw some tips and trick to build my own, but steps seems not as simple as i think...any recommendation of easier stuff to build the GG?? say, UV ring, 1 of the side screen sanded by sand-paper? is this the right way to build a Focusing Screen??

a.1) what's the purpose of Focusing Screen? making bokeh ? or better DOF? or???


b) WHAT STUFF is inside the adaptor (Tube) to rotate the image we are focusing? do you get what i mean? say, if you hold the SLR lens and look inside it, you'll found that the image is FLIPED one, isn't it? so...in the Tube of the 35mm adapter what is the stuff to tweak/rotate the image so that the Camcorder c'ld able to capture the right image?

Hope this clear...haaa...thanks ya!!!
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Old March 23rd, 2009, 04:44 PM   #2
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Quote:
Originally Posted by Mac Treouser View Post
a) Focusing Screen (GG). s'ld i buy for better result? i saw some tips and trick to build my own, but steps seems not as simple as i think...any recommendation of easier stuff to build the GG?? say, UV ring, 1 of the side screen sanded by sand-paper? is this the right way to build a Focusing Screen??
If you're building a vibrating adapter, then you can simply purchase a premade focus screen from Canon, for example. You can also find them occasionally on ebay. If you're building a spinning adapter, it becomes a bit more difficult. I used a very large focus screen made out of glass and cut it into a circle.

Quote:
Originally Posted by Mac Treouser View Post
a.1) what's the purpose of Focusing Screen? making bokeh ? or better DOF? or???
Both. The focus screen helps make a shallow DOF. The out of focus areas are the bokeh.

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Originally Posted by Mac Treouser View Post
WHAT STUFF is inside the adaptor (Tube) to rotate the image we are focusing? do you get what i mean? say, if you hold the SLR lens and look inside it, you'll found that the image is FLIPED one, isn't it? so...in the Tube of the 35mm adapter what is the stuff to tweak/rotate the image so that the Camcorder c'ld able to capture the right image?
The image from your DIY adapter will be flipped. You will either have to use an external monitor that is upside down to help you shoot - you will also have to flip the image when you edit it. Or you can shoot upside down (you actually can get used to doing that) and then flip it in post.

Commercial adapter makers offer a flip module or have one built in. It's unlikely that you can build your own flip module at a resonable cost because it uses custom designed prisms.

You may, however be able to use a commercially manufactured flip module with your DIY adapter.
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Old March 23rd, 2009, 05:27 PM   #3
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You might be better off buying in the do it yourself kit from Redrock. There is a whole lot more to doing it than I can repeat here quickly and comprehensively.

Here's a link to a clip of mine. There are better ones and the most suited are the project box versions as alignments are easier.

YouTube - AGUS35 APVE PARTIAL DISMANTLE

Groundglass. Aluminium Oxide 5 micron grade in a water slurry to grind.

90degree Prisms. At least 70mm hypotenuse face by at least 35mm common thickness across faces.

Achromatic dioptre. 4+ to 7+ is fine for flip version, 10+ is better for non-flip.
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Old March 24th, 2009, 12:22 PM   #4
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Hi thanks friends...

GG/Focusing Screen: Do the 35mm adaptor need the Spin or Vibrate screen? i saw some tutorial about the GG use on the adaptor without spin or vibrate and some just use a transparence plastic to build it...is it true and posible? what's the different in between a screen and a plastic? c'ld able to achive the bokeh result so?

What bout Magnifying Glass? do this kind of glass posible to apply in the adaptor and Which part s'ld i place it to? Is the Magnifying Glass equal than Macro?

Sorry for those fool question...i've try to do some research online but can't get a proper answer...that's why showing foolish here...haaa...

hope to hear from the experts and you guys soon!!!:D appreciate!!
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Old March 24th, 2009, 02:42 PM   #5
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It's true, you can build an adapter using a static GG (not spinning or vibrating) but it is very limiting and you are likely to see the "grain" of the GG in your footage, especially if you use an HD camera. You would have to grind the glass very fine which means that the bokeh may not be as pleasing. The spinning or vibrating is used to make the grain invisible. There are still some limitations with those designs, but they are still more flexible than a static adapter, in most cases.

Plastic or glass is accpetable. For example, the SGBlade adapter has interchangable GG. One is made out of glass, the other is made out of acrylic. They have different characteristics and different results.
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Old March 24th, 2009, 10:06 PM   #6
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Hey Thanks again!!!
Atleast i got the idea bout GG's meterial now.
The following steps is my Big Question, From Camcorder to the SLR lens.What's inside the tube in between the Camcorder to SLR lenss? And where do those stuff place at? Do i really need a Achromat Lens or Macro +10? How simple c'ld i build the Adaptor? Might need your helps here...thanks!!!
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Old March 24th, 2009, 11:09 PM   #7
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Explanation and plans:
DOF depth of field using 35mm lenses
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Old March 25th, 2009, 12:43 AM   #8
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Quote:
Originally Posted by Mac Treouser View Post
Hey Thanks again!!!
Atleast i got the idea bout GG's meterial now.
The following steps is my Big Question, From Camcorder to the SLR lens.What's inside the tube in between the Camcorder to SLR lenss? And where do those stuff place at? Do i really need a Achromat Lens or Macro +10? How simple c'ld i build the Adaptor? Might need your helps here...thanks!!!
This is a simple diagram of a mid-format spinning adapter I made a while back. You can use the same concept for a 35mm adapter. And if you want to build a vibrating adapter, just replace the spinning disk with the vibrating rectangular GG. You can build the vibrating adapter in a tube. You need a box to build a spinning adapter.

This is just one design to give you an idea of where stuff goes..or at least how it went in my DIY adapter:
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"Rotate Stuff" inside the 35mm adapter?!-adapterdiagram.jpg  
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Old April 1st, 2009, 10:05 PM   #9
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Marcel, I built an adaptor similar to yours. You can see a diagram below.

I just recently missed out on a rental because the director saw the circular pattern of my GG spinning in part of the images I showed him during my demo. I usually donít see these lines in well lit conditions, but I have to admit it bothers me too, when I do.

Did you ever have this problem with your adaptor and do you have any good ideas for how to eliminate it? I thought about increasing the speed of the motor or getting one that spins faster.

(My GG is the one that came with the Redrock kit.)

Martin
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Old April 2nd, 2009, 09:21 AM   #10
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If I'm pointing to a bright sky and have the 35mm lens stopped down to f22 I can see the semi-circular grain just a bit.

I made my GG out of real glass. It was a very large focusing screen with a very fine ground surface on one side.

I believe that the GG from Redrock is some sort of acrylic. It probably loses more light than my glass GG. That usually means that there is more of a limit to how far you can stop down on the 35mm lens before you start seeing grain. Do you remember if you had a bright, flat surface in the image where you can see the grain and what the fstop was?
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Old April 6th, 2009, 12:38 AM   #11
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Marcel, sorry for the delay in responding to your question. I've been traveling.

Yes, the problem is most severe when pointing at a light flat surface, like a white wall. The more I stop down, the more I see spinning arcs.

This seems to argue for a vibrating and not spinning GG. Have you ever made a comparison?

Mind if I ask you where you got the focussing screen you used to make your GG?

Ever tried speeding up the motor? I've been experimenting with that and it seems to help in some situations. The P+S Technik and the new Redrock have speed controls. I guess there must be a good reason for this?

Martin
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Old April 6th, 2009, 09:10 AM   #12
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Actually, the problem is much more noticible on vibrating GG in general. Most can't stop down past f4 or 5.6 under the best conditions. It also depends on how finely the GG is ground but in general, Spinning GG can handle higher shutter speeds and being stopped down farther. Increasing the speed only speeds up the movment of the arcs that you see. Changing the speed on a spinning GG helps save battery usage at the lower speeds and can still handle the higher shutter speeds at the faster spin rate. But it doesn't really help much on blue skies unless it is spinning very slowly to start with.

Since I now have an SGBlade, it has a variable speed GG and two different types of GG so I've been able to experiment a lot.

Take a look at this test video. The first minute and 15 seconds was shot at f8 and the rest at f4. You can tell when it moves from f8 to f4 because the DOF becomes more shallow. You can't see any grain in the sky even at f8.

SGBlade Test / XH-A1 w / ROTOrazor 2 By Marcel Van Someren On ExposureRoom

I bought the GG from a guy on ebay who sells large pieces. Remember I had to learn how to cut glass in order to make a circular one. It's not for the faint of heart :).

If you like I can find his email address and PM it to you.
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