35mm issue: will macro lens help me? (test footage without macro or achromat)

J

juraj

Active member
Hi, i am trying to make my first 35 mm adaptor and need some advice. Footage you see under i shot without macro lens or achromat, because i dont have any yet. Just Sigma SLR lens, PVC pipe, GG and camcorder (about 1 inch from GG). Do you think, that if i buy macro or achromatic diopter, problem with hotspot will gone? Please dont look at quality of GG, i am still searching for some better. Thanks.

hotspot1.jpg



hotspot3.jpg
 
The GG probably has a lot to do with the hot spot issue. If the light is not diffused enough by the GG then you will get a hot spot much like the one in you picture. Also, without an achromat/macro, you might need to move you GG even further from your camera which will also help with the hot spot and vignetting.
 
1 inch from the GG to the camcorder is too close really, and will cause massive hotspotting. Like snodart says, increasing distance between GG and cam will help even out the vignetting/hotspot.
 
thanks for your reply. First picture has been taken with spinning "sandpapered" CD, second with static piece of thin glass (grinded with sandpaper too). Do you think, that i should grind it more? Or what would you recommend as the best GG?

If i move my camera further from GG, i am not able to zoom and focus to the image properly - it not covers full frame.
 
I am going to buy one. Achromats are too expensive for me (Century Optics), but i found very affordable Kodak macro lens, hope that will be better than Asian ones.

What about the GG? Could you recommend me some technic for grinding glass? Or is it better to buy the Nikon focusing screen?:dankk2:
 
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Before you buy a macro you should know that the achromat is used to prevent chromatic abberation. That's the blue and red halos that are created because differing wavelengths of light bend at differing rates. Check out surplus shed http://www.surplusshed.com/ . They will probably have something that will work for you and cost less than the Kodak macro.

I am just getting started on mine and have a question also about this. My impression was that they hot spot was introduced between the 35mm lens and the GG rather than between the camera and the GG. Which is it or is it both?

Thanks and I hope you find the lens you need.
 
Mlimbolimbo, thanks for the link. But since i didnt found any achromat of mine diameter, i am going to buy the Kodak from e-shop in my country for circa $37. If somebody here has an affordable macro or achromat for sale, i´ll buy it:)

About hotspot - i exactly dont know. Wayne and Snodart are experts, so i´ve more abrade (?) my GG and i think, it is now precise enough ("sandpapered" microscope slide glass). So i think that now it is just issue of missing macro. Because, if i place between GG and camcorder a magnifying glass, results are much better. Sorry, that i havent an example.

If i´ll susuccessfully dismantle my old SLR, i´ll try place its focusing screen as a GG. But its a soviet machine :kali: (http://www.zenit.istra.ru/archive/zenit-e/zenit-e.jpg)which is not easy to break (but has plain focusing screen!)

Iam sorry about my English, hope, you´ll understand me:-)
 
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juraj, mlimbolimbo is correct. Without a quality achromat, your images will suffer from chromatic aberration. You might as well put the money that you would spend on a cheap macro and put it toward a quality one. Redrockmicro has and excellent 55mm achromat for $160 that works great with SD cams like the DVX. It even comes with the 72-55mm step down and the 55-72mm step up rings, which would run you about $10 each new otherwise.


mlimbolimbo said:
I am just getting started on mine and have a question also about this. My impression was that they hot spot was introduced between the 35mm lens and the GG rather than between the camera and the GG. Which is it or is it both?
Click to expand...
It is both.

When a GG is too transparent, the cone-shape of light that is coming from the 35mm lens aperture will "burn" a hot spot onto the GG. The GG needs to be just the right level of translucency to diffuse the light out evenly over the GG. If it is too transparent, you will get the hot spot. Too opaque and you will have too much light loss and other issues.

Also, if the GG is too close to the macro/DV cam, hot spots and vignetting may occur. I'm honestly not sure exactly why, but it can make a big difference in many cases. My guess is that it has to do with the dynamics of the camera's lens, the macro lens, and the plano-convex (if plano side is facing cam) all working together.
 
Snod, i know about poor quality of macros, but achromats are honestly too expensive for me. Maybe in future, but this time i need 35 mm adapter for my Canon Optura 60 camcorder and shooting some student films, or non-budget music videos.:)

With my new GG, which is about 2 inches from camcorder, the image looks better, see examples. I think, the hotspot almost gone... I maybe need to make my GG vibrating, because its grainy. And macro of course - it is not possible to zoom more, see black borders (my GG size is only about 20 x 30mm). My lens is Sigma 28-90mm.

fg1.jpg



fg2.jpg



fg3.jpg
 
Snodart, thanks for the info. I think I am going to set up a few adjustable mounts to test all this before building anything permanent.
 
juraj, those new grabs look much better as far as the hot spot goes. You just need a good GG and a macro. You can get a +10 Asian macro off of ebay in the mean time for $20. There will be plenty of chromatic aberration, but otherwise it will work until you can get an achromat.

mlimbolimbo, sounds like a good plan. Be careful, this 35mm adapter stuff is addicting :)
 
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