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Old May 14th, 2005, 10:36 AM   #1
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Struggles, but getting there

After getting back into the game of DOF, I was still having some problem with vignetting etc. And although people like Dan, Bob Hart and Oscar were tooting bigger back lens make a large viewing area on the GG, I never changed my Sigma lens 35-105mm because the bayonette mechanism worked perfect with what I had constructed.

Big mistake.

I have a few lenses that I have picked up over the last 8 month or so and since I was still having problem with vignetting etc, I tried a new lens knowing that I would have to start over on the mounting plate and BOY what a difference!! Where before, my viewing image was about the right size for the GG, fit almost top and bottom of my CD, the new lens goes above and beyond making a huge image!! I know now that vignetting will not be a problem because of the size of this thing!!!

Back to the drawing board for a new mounting plate and measuring for a new focal length, but I think this time it will be well worth it. Inspiration sometimes hits you when you least expect it - and sometimes it take being told 5,10,100 times before you finally click - but thanks to Dan for being the biggest champion on the LARGER image, make a large viewing area and therefore, less chance at vignetting.
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Old May 14th, 2005, 11:23 AM   #2
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Wait until I get my old Rolleicord in front of my GG...I'll be hitting Dan over the head with my extra large image!
Leo, I'm looking forward to some test footage with your new lens. What lens is giving the best results?
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Old May 14th, 2005, 11:57 AM   #3
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It is a cheap looking - Mirage 135mm with the screw end instead of the bayonettte.
Right now, the image is looking better, but I still need to get closer to the GG, a little far away right now for my liking because there is still hints of hotspots at the distance I am at. Also, the GG, although great in my books, continues to come unglued from the CD, even after repeated sprays of glue, so I am going to need a new method for this.

http://dvstuff.250free.com

The stuff is up there now Oscar. I am also going to switch GG's again and see what happens with the new Lens. Maybe I can go back to the Press & Seal - and see what that yield - I liked the Press&Seal because of the little light loss from it.

Posted some new stuff from the last hour or so. Getting better, but I need a new GG CD without blemishes and a way to make the mylar stick without coming off or bubbling! Anyone got ideas?

Last edited by Leo Mandy; May 14th, 2005 at 01:14 PM.
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Old May 14th, 2005, 06:28 PM   #4
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That's about 10 times better footage than before...
I think if you put a condenser between the 135mm and the GG, close to the GG, you'll get rid of the hotspot maybe also with the press/seal thing.

I use all lenses with screw mount, it's old so you can find lots of cheap lenses. Some of them are really good. I have the same thing, 135mm gives best results.
Maybe you remember, this one is 135mm (no hotspot/vignetting):

http://doublecam.250free.com/135mm.jpg
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Old May 15th, 2005, 12:59 AM   #5
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Talking about lenses in terms of focal length without talking about maximum aperture is like saying "red cars are fast."

Looking at the back glass size is a backwards way of trying to get the crux of the matter. Lenses with big apertures generally have larger diameter back glass. But the aperture is the key, not so much the focal length nor the back glass.

I can show you a 135mm lens that works great, and another that doesn't. Try stopping down your lens and see for yourself. It's not the big back glass that gets you brightness and lack of vignetting. It's the big aperture.

http://www.dvinfo.net/conf/showthrea...871#post312871
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Old May 15th, 2005, 06:50 AM   #6
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I meant to ask about the aperture.
OK...the lens I used for the image I posted.
f=135mm
1:2.8

Red cars are faster than any other color, no doubt. This thread is terribly cross posted, I was about to call you Jonathan again, but future readers will not understand.
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Old May 15th, 2005, 10:15 AM   #7
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My mirage has an apareture of 1:2:8, just like Oscar's - I agree about the aperature, but after testing out 4 different lens and comparing the image size and brightness, I found the one I wanted without having to really check the apareture number itself.
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Old May 15th, 2005, 01:43 PM   #8
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Mandy,

The bigger the aperture (lower F-stop) the more flexibility it will give you since you can alway stop it down to a smaller aperture if you want or need to. It gives you more light - what some people are thinking is a "bigger picture." But keep in mind these lenses are designed for SLR film.


As you go up in aperture, DOF goes down, which is what we want. Price usually goes up!


Oscar,

Even red Skodas?? ;-)



BP
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Old May 16th, 2005, 07:08 PM   #9
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Hey Oscar,

How are you dealing with the fact that the camera has to be further away from the object now that we are dealing with the 135mm lens? With the 35mm, I could get in relatively close, but now I notice that I cannot focus when in close and have to move the camera back quite a ways. Did you just deal with this?
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Old May 17th, 2005, 06:11 AM   #10
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You'll get nice close ups when shooting indoors, but it's more suitable outdoors. (the image I posted was shot from about 5 meters)
I'm looking for a 70mm or something with a big aperture myself. And a better 50mm one.

Bill, a red Skoda would be more like the title of this tread I think: "Struggles, but getting there."
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Old May 17th, 2005, 05:50 PM   #11
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Yes me too,

I have a canon 50mm, nice lens with some dust spots, but the back lens is not nearly as big - and when shot against a GG, the image is alot smaller than with my Mirage 135mm. The search continues.
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Old May 18th, 2005, 02:14 PM   #12
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Mandy,

Like I have been saying, the back lens size is not the benchmark you want to use for lens decisions. Use the aperture, aka the "F-stop" to pick a lens. What is your 50mm? For example, F1.4, F2.0, F2.5, etc.
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Old May 18th, 2005, 05:28 PM   #13
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It is Canon 50mm 1:1.8

I understand what you are saying, I don't know all the details or the mechanics of determining the apareture size, but when I test it up to the GG, I can see a bigger image - to me, that is enough.
I really don't also have alot of lenses lying around to pick and choose, so when I find one that works, I don't care about anything else except my luck!
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Old May 18th, 2005, 11:50 PM   #14
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You know everything you need to know about aperture size by looking at the F-stop number and the focal length.

A 50mm F1.8 works fine with a static adapter. A 50mm F1.4 works even better. The bigger the aperture, the shallower the depth of field, and the more light. Win/win.

You can also stop down a F1.4, to F1.8 or smaller, for more depth of field, by adjusting the aperture. You are not stuck at F1.4.
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Old May 19th, 2005, 05:58 AM   #15
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A 50mm F1.8 doesn't work well enough with me. Not too bad, but my 135mm 2.8 gives a much better image. I have a 58mm lens with a 1.4 aperture but it'll take me some time to test it, because it has a bigger bayonet mount.
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