stock lens at telephoto v 35mm adapter

Snodart,
I respect your first hand experience with the external filters making a difference though i didn't find that to be true when I tested. I don't think the DVX should make any difference. Having heard your account though I will try to test again when I get a chance. I'm skeptical though, but will remain open minded.
I can't follow the theory your presenting about aeriel images and such though, and I'm not sure that Dennis' "exotic materials" would make his adapter respond differently. In his post on DVInfo.net Dennis didn't repeat the "overexposed GG" idea.
At least we finally have someone who says "I saw this with my own eyes" The only thinking that makes sense to me in this is if the HVX ( or DVX ) internal filters were bad. That's quite possible i guess.
A very good tech I know who rents out Sony F900's buys special HD quality glass for his internal filters.
- Lenny
 
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=Prodigy= said:
I know what you mean! I shot at the beach with my 35mm adapter and wow!

To prevent stopping down too far on the lens I utilized the HVX's ND filters, closed the HVX iris just a little more, and sometimes if that was not enough I just changed my shutter speed as last resort.
Click to expand...

wow... is the sun brighter elsewhere in the country.
 
It seems that several have tested internal vs. external ND's with the HVX and found no difference.

TimurCivan said:
Also Justin, Wayne kinney has an example of your eternal 1080 sunny day test. I shot it last month. though maybe i'll make another one tommorow for you guys. what you will find is that the resolution and highlight handling of a 35 adpter system is dependant on thelens itself. the better glass you use the better it looks.
Click to expand...

Tim, do you remember the settings and such for the test? I would just be interested to hear more about it.

As far as the resolution and highlight handling, no matter how good the lens is, the image still has to end up on the GG. If the GG does not do a perfect job, then the image will suffer (even if it is very slight). The GG is the weak link with 35mm adapters IMO. There are some great GG's (focusing elements) being used now, but I would say that the chances are slim that any of them do an absolutely perfect job. It is just the nature of adapters (which will always be amazing in my book).

I think the one way to test the theory that I posted above would be to use a very bright GG (3 micron aluminum oxide or so). I think that the effects would be more apparent this way. It could be that the newer GG's being used now are just very good at their job.

I will say this: if a GG is capable of correctly representing every light ray from the lens as the total image on its surface (GG's surface), then it would not matter at all if internal or external ND's are used. I just don't think that most GG's can do this... 100%.

TimurCivan said:
he uses exotic materials in his GG's that apparently flare if too much light hits them.
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:huh:
Has anybody done the ND test with the brightest version of the Brevis screens?

I just realized that we hijacked the heck out of this thread. :huh:

Anyway, I might see what I can put together as far as tests go in the next few weeks (so I can stop thinking about this topic). For now, you will see me with ND's in front.

P.S. to keep this great discussion going, and in hopes of coming up with a definitive answer...

Here is a grab from one of my early GG tests.

hotspot.jpg


The GG that I was using had a surface that was too fine (too translucent). With the 35mm lens at f/22 the light rays created a nasty hot spot on the GG. Some of those rays did not stop at the GG, they kept going right on though.

I'm just playing the devil's advocate here, but if I wanted cut down the intensity of the light so that I could pick up some more of the details in that hot spot (like the edges of the tree, or some changes of value or tint in the sky), would it be better to put the ND's in front of the 35mm lens or behind the GG?

This is an extreme example of course, and yes... the image would be bunk in either case, but it sure makes me wonder...
 
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yea but yours is a static adapter isnt it? The statics dont enjoy being stopped down.
 
Not sure why one of my earlier post ended up here... anyway, I deleted it.
TimurCivan said:
yea but yours is a static adapter isnt it? The statics dont enjoy being stopped down.
Click to expand...

The Snod35 is a vibrating adapter. The reason that the image failed in the case above is because the GG was too transparent... it did not hold enough of the image. The GG used for that image is long gone now and I am using a GG that is more translucent. Regardless though, the point is that some light (be it a small or large amount) will make its way directly through the GG (just not as dramatically as in the image above).

Again, if a GG is capable of correctly representing every light ray from the lens as the total image on its surface (GG's surface), then it would not matter at all if internal or external ND's are used. I just don't think that most GG's can do this... 100%.
 
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TimurCivan said:
wow... is the sun brighter elsewhere in the country.
Click to expand...

Yes, when filming around light colored sand, water or snow the area is brighter.

Sand, water (for the most part) and snow is like shooting standing on top of a bounce board.

On a bright and sunny day, snow and sand can be blinding compared to other landscapes at the same sun level.

EDIT: was this a joke that went over my head? Seems to self explanatory
 
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yea usually a condenser lens helps remedy the hotspot. the real problem is like in CCD design, the light hitting the cneter of the GG/CCD is at a perpindicular angle, the light hitting the edges is at a ~20degree angle ( or what ever it is) and hence it seems to have a vingette. thus the light being collected by the HVX lens is now not only direct through the middle, but now its off axis twice at the edges. the light rays that are bouncing back toward the middle from the GG are the ones being seen by the HVX.

Its a miracle 35adapters even work.
 
Snod,
(where did you get that name by the way?)

The overexposure in the shot you show doesn't seem to me to be do to whether int or ext filters are used, but is just due to a combination of factors - nature of the lens, the f22 stop, nature of the groundglass, etc that contributed to extreme vignetting.
Seems like a separate issue, unless you could compare identical shots with identical ND either internal oand then external to match exposure.

- Lenny
 
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