I think that what you should be interested in, is how much F stops you loose on the camcorder using the adapter under optimal conditions (your best lens, biggest aperture etc.)
I made this side by side for the wax glass: http://s01.picshome.com/4b4/dv-wax.jpg
Lets say the one without the adapter was 4 stops (on the camcorder) and the one with the adapter was 2 stops. So I loose two stops in this case.
Maybe I'm wrong, but this makes sense to me. With bright sunlight I also loose 2 stops, but because you get so much more tonal range on the GG, I make it 1 stop to make it brighter.

I think that what you should be interested in, is how much F stops you loose on the camcorder using the adapter under optimal conditions (your best lens, biggest aperture etc.)
In fact not me, but lots of people cares about this, so I just wanted ty try it out...

Lets say the one without the adapter was 4 stops (on the camcorder) and the one with the adapter was 2 stops. So I loose two stops in this case.
Maybe I'm wrong, but this makes sense to me. With bright sunlight I also loose 2 stops, but because you get so much more tonal range on the GG, I make it 1 stop to make it brighter.
Yes, I uderstand it same way. But if I tryied it, it showed me F4 without adapter and F3.2 with adapter and same scene (FOV). I have in front of Primary lens with F4... So, what I do not understand is, how can I get F3.2 from F4 if I put GG and next F4 in front of it... (both scenes were at 1/50s).

Just to compare naked camere against camera with 35mm make me sense... :/ Do it then. (use that 1.8/50 this time).
Your previous test proves only the compensation between apertures settings on the two lenses : SLR and camcorder. Now...where did I put that half-a-stop?(;-)<

Just to compare naked camere against camera with 35mm make me sense...

No, it does not work that way.

What I do not understand is, how can I loose 0.5 Fstop, when I'm using F4 in front of...

There is no correlation between the aperture rating or setting on the SLR lens and the camcorder lens.

I am surprised, that I got same scene at F4 without and F3.2 with. What about the F4 of takumar ? Where is this number ?

The reason you got F3.2 with the adapter is the camcorder opened its aperture to admit more light, to make up for the loss of light due to having an adapter and a lens in front.

I expect something like this : If I have F11 by naked camera, I should have F11-F4(of takumar)-F?(by convertor)=~F6 ;-)

Nope, it doesn't work that way. The F-stop rating of each lens is a ratio of focal length to aperture, *for that lens*. You cannot add and subtract these ratings between lenses because they only describe the ratio for each lens, length vs. diameter.

But there must be something about the takumars F4, right ?

Nope! :-)

F-stops means what ? Count of the stops between two Iris setups, or the result after subtraction between them ?

Neither. Again, it is a ratio for one lens, to describe the aperture size of that lens.

OK... I did this - I took Takumar 1:4 at 70mm and get this numbers :

Camera : Takumar
F11 : F4
F11 : F5.6
F6.8 : F8
F4.8 : F11
F2.8 : F16
F2.4 : F22
F1.6 : F32

But if we are talking about "loosing some F-stops", how do I get this number ?

You showed the number right there. It is not a simple numeral, it is a *step* in a logarhythmic progression.

The key to understanding f-stop progression is the knowledge that each successive f-stop increases logarithmically by the square root of 2 (i.e. 1.4)
.
f1.0 f1.4 f2.0 f2.8 f4.0 f5.6 f8.0 f11.0 f16.0 f22.0

Note the doubling/halving relationship between each alternate number:

f1.0......f2.0......f4.0......f8.0......f16.0
......f1.4......f2.8......f5.6......f11.0*......f22.0

* by convention, f11.2 is rounded down to f11, and similarly, f128 to f125.

(for all testing, camcorder @1/60):
If the camcorder "reads" in AE say... 4 (iris) for a certain scene, than with the converter (and lens wide open-which ideally should be 1.2, hehehe....) close the iris on the SLR lens till the camcorder "reads" again 4. If the SLR has a 1.4 (as max), the camera should have at least the same reading through the Fresnel and the lens @1.4 as all by itself.
Daves, if you only lose 1/2 stop due to max 4 on your Takumar, imagine how sweet life would be using a brighter lens...........

I also think there is some confusion due to a typo or mistake here. If the camcorder reads F4 with no adapter in a given situation, then with the adapter and SLR there is no way you can close the iris on the SLR until the camcorder reads again F4. The more you close the SLR, the more the camcorder will open its iris, thus reading a lower number, not the other way around. Dave's tests demonstrate this nicely for me to cut and paste:

His Camera : His Takumar
F11 : F4
F11 : F5.6
F6.8 : F8
F4.8 : F11
F2.8 : F16
F2.4 : F22
F1.6 : F32

If the camcorder reads F4 with no adapter in a given situation, then with the adapter and SLR there is no way you can close the iris on the SLR until the camcorder reads again F4.
I might be wrong, but... try it yourslef Bill. Get a FAST lense (1.4 or better) and a Beattie and let us know the findings. (moving it is not relevant for the purpose)
Although on the surface it may not make much sense to get more light out of a source adding a lens and a focusing screen, the results seem to contradict "common sense": (or don't they?)
http://dandiaconu.com/gallery/ALL-CLIP-TESTS/IMGA0660TU?full=1
We all could "smell the brightness difference" if holding a lense close to skin on a sunny day..... (imagine a poor ccd's opinion on the matter)
The more you close the SLR, the more the camcorder will open its iris,not the other way around.
Who said is the other way around? Give me the "offender" and I'll ... hmmmm, ....just you watch.....

Who said is the other way around? Give me the "offender" and I'll ... hmmmm, ....just you watch.....

The Daves' camera said it's the other way around. The more he closes his SLR iris, the wider his camcorder's iris opens.

Originally Posted by Bill Porter
The more you close the SLR, the more the camcorder will open its iris,not the other way around.

Originally Posted by Dan Diaconu
Who said is the other way around? Give me the "offender" and I'll ... hmmmm, ....just you watch.....

Originally Posted by Bill Porter
The Daves' camera said it's the other way around. The more he closes his SLR iris, the wider his camcorder's iris opens.

Guys, maybe I do not understand you enough, but you both are saying the same... More I close SLR, more iris open on Cam.

Dan is saying the opposite:

<<If the camcorder "reads" in AE say... 4 (iris) for a certain scene, than with the converter (and lens wide open-which ideally should be 1.2, hehehe....) close the iris on the SLR lens till the camcorder "reads" again 4. If the SLR has a 1.4 (as max), the camera should have at least the same reading through the Fresnel and the lens @1.4 as all by itself. >>

I have never used a fresnel so I can't say whether he's right or not, but your numbers (Daves) disagree with what he is saying.

Guys, guys, guys... I still do not understand, how someone can say "My adapter is loosing 2 stops" - its nosense, I think. So long until you say "My adapter is loosing 2 stops at 50mm with 1:2" or something like that. Today I have tried lens 1:1.3 and I have F2.4 with adapter and F2.0 without adapter, both at 1/50s. Next interesting thing is, that this lens does not produce any vignetting !

It's not nonsense, because your adapter hás less light-loss with the 1.3 lens. The light-loss depends on the lenses used and the GG together. With most telephoto lenses you'd loose much more light.
The only real question is: does the adapter give too much limitations compared to the camcorder without the adapter. The answer is probably, yes if you loose 4 F stops and want to shoot indoors. No if it looses 2 F stops or less in any circumstances.

It's not nonsense, because your adapter hás less light-loss with the 1.3 lens.But thats the point... If some one says "my adapter has 2 stops light loss", he told nothing - if he will not tell also the type of lens. Right ? With 1:1.3 my adapter is gaining about half F stop... But this does not mean, I will gain with 1:4 too.
Whats the point of this issue ? If someone come here, to DV and starts to read... And he see : ManA : hey, buddy, my wax adapter is loosing 2Fstops. and then ManB: hey, dude, my spinning CD is loosing 0.5Fstops... But he do not know one important thing... manA is using lens 1:4 at 50mm, manB is using 1:1.2 at 70mm. In case both will use 1:1.4 at 50mm, manA will say 0.5Fstops and manB will say 2Fstops (example). See my point ?
Maybe Im still completely wrong. I just want to undersand it.

The light-loss depends on the lenses used and the GG together.I guess this is the answer for me... So... If someone tells his adapter has 2Fstops loss, its zero predicative value, until he mention the lens he is using...

Hi Daves,

I have not look at adapter threads for while.

You're saying with F4 lens losing 1/2 stop and with F1.3 lens gaining about 1/2 stop.

That is about 1 stop difference, although there is 3 stops difference bwtween the lenses. It not make much sense.

I was originally wrong about adapters. I thought at F1.0 lens does not lose any light. Is not the case.

You're right, you can gain F stops with adapter, if these are the measurements and yes, if someone says they lose stop or two it does not make sense if is not referenced to something.

You're right you must reference light gain or loss to certain F-stop of 35 mm lens.

If everyone did testing same way, e.g. at F2.8 of 35 mm lens then we would have some reference to which compare adapters.

There may be some discrepencies, F-stops are related to dimentions of lenses, how much light goes through lens is measured in T-stops.

If your 1.3 lens was made for larger format, that may explain descrepency in your measurements.

Radek

If your 1.3 lens was made for larger format, that may explain descrepency in your measurements.The lens is from some kind of movie projector, I get it for free, when throw away some projectors from very tiny old local cinema.

It could been 70 mm projector or medium format slide projector. That would make sense.

GG will naturally lose light. It is 35 mm lens that is responsible for gaining light, also condenser lens. To see how much GG and condenser, which make 35 mm system, are losing, you could measure amount of light coming off 35 mm lens, then add GG and condenser to see how much light have then. May lose 3 F-stops.

When P+S talks one or two stops, is probably on Canon or other interchangable lens camera and adapter uses relay lens.

Radek

GG will naturally lose light.
True! But we have a different story when it comes to focusing screens!!!! For the same lens, (let's say a 1.4/50), some GG will lose between 1 to 3 stops and a good focusing screen will gain some 1/2 to 1 stop) Big difference! Why do you think Nikon, Canon, etc use focusing screens in SLR and Digital cameras instead of just GG?

Dan, it is physically impossible to start with a set amount of light and gain more in the process of scattering :)

Actually the screen always loses light but the 35 mm lens is capable of increasing the amount of light compared to the camera lens.

Radek

Quite possible! I was just pointing out that you can't end up with more light than you put into the system (which is what the post sounded like it was saying - not sure if it is or is not).

I think what Dan is trying to say is that if you were to measure the amount of light that a particular lens captures it would read a particular F-stop on a light meter. However, keep in mind that at the back of this lens the light is not uni-directional. It's being spread out in all directions away from the back of the lens. Now, if you were to put a focusing screen between the back of the lens and the light meter you are capturing some of those light rays that would otherwise pass the light meter without being read. The screen captures those light rays and makes them unidirectional. In this case you would most likely gain F-stops.

It's not saying that you're reading more than what's coming in. It's saying that your losing less light due to the fact that you're capturing those rays that would have normally gone right by the light meter, or in our case, the CCD's in the camera.

One must keep in mind that if you're going to compare light loss between all of our different adapters, there has to be some sort of standard. Otherwise you have no way of comparing. You wouldn't try to benchmark one computer to another with one playing the newest Splinter Cell game with all the detail,s effects, audio, etc. turned on while the other one is playing the first Doom game ever made. It's not a fair comparison.

Probably everyone has a 50mm lens. Probably most of us here have Canon lenses. Why not record what the F-stop is with the lens attached to the adapter and camera, then again with your focus-screen/ground-glass/whatever in place. Then you'll get an idea of what you're losing, and at the very least, you might be able to figure out a better way of capturing more of those light rays that would otherwise not be seen by your cameras CCD's.

Court

Somehow the point of the light measurement is totally lost.
If someone wants to know how much light his adapter is loosing, he should measure how many f stops his camcorder increases using the adapter.
He should do this with the best equipment he can get, including the lens, condensers, GG etc. What's the point doing anything else than that.
If you only want to know what the light-loss is on an oscillated GG compared to a spinning frosted glass or a wax glass, than you should test them with the same lens etc. to measure the difference.
It becomes a strange issue when you don't consider the lens a part of the adapter. It's strange because it's the most important part.

Dan, it is physically impossible to start with a set amount of light and gain more in the process of scattering
Of course she's-a-flat, and she's-a-not spinning at-a-all.. (what am I... to get burned to the stake?) (;-)<
Start with the sun, get a lens (the focal does not matter much) and smell the brightness increase on your skin.... (;-)< Looks like I posted all those pics for myself and I am just talking to myself.... I had two clips on my site with four different screens: two GG and two focusing screens (one from Beattie) They were all mounted on a "rail"(one after the other one) traveling behind a lens (1.4/50) Camcorder was set for the brightest screen. Nobody watched them, so I took them out. If I still have them, I'll upload them again. None of the present camera manufacturers are using GG!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
They all use focusing screams!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Light it up!

i saw dans video, and it seemed like it was getting more light than before... seriously.

i saw dans video, and it seemed like it was getting more light than before... seriously.

Of course... When I was in the beginning, I project image on GG, then I put piece of fresnel on it, and whole image shine up twice more... I have this tests also on my page... But as Dan said... Everyone is pushing his theory and noone looking on tests from real live :)

EDIT:

Look here... Guess its enough to prove it...
http://web.datriware.com/gfx_photos/articles/p850.jpg

GG and fresnel attached to it. Not beattie, maxwell, or so. Just fresnel.

I was in the beginning, I project image on GG, then I put piece of fresnel on it, and whole image shine up twice more...

Yes, but did it "shine up" to the point where the video camera closed its aperture compared to no adapter at all? That is what Dan is saying. But your adapter shows this to be untrue.

But as Dan said... Everyone is pushing his theory and noone looking on tests from real live :)

That's not accurate. Not many people have tried both a GG and a fresnel or focusing screen, but nobody in this discussion is speaking from theory without "looking on tests from real life." We've all built something in real life; some have tried more combinations than others.

Look here... Guess its enough to prove it...
http://web.datriware.com/gfx_photos/articles/p850.jpg
No, what would prove it would be to show the F-stop with the fresnel, compared to the F-stop with no adapter at all. Follow? Just showing one picture of one setup doesn't prove anything at all about increasing brightness and decreasing iris over no adapter at all.

No, what would prove it would be to show the F-stop with the fresnel, compared to the F-stop with no adapter at all. Follow? Just showing one picture of one setup doesn't prove anything at all about increasing brightness and decreasing iris over no adapter at all.
This test is an answer to question what give us more light - GroundGlass or GroundGlass with Fresnel. I think the image is clear. And you do not need to do the test to prove it, you see it. And the test that I gain more light with adapter than without I already did and posted before.

Yes, but did it "shine up" to the point where the video camera closed its aperture compared to no adapter at all? That is what Dan is saying. But your adapter shows this to be untrue.
Yes, as I wrote up. But you have to have pretty good lens. I found some 1:1.3 without iris and focusing. Its static lens. And these lens are damn expensive. But anyway... Imho I´m shooting with 1:4 and have no problem. If you saw my nigth movie, its done by 1:4 at 70mm without any post.

Where did you get your fresnel from Dave?

Where did you get your fresnel from Dave?
Bought on eBay. Im from Europe, we do not have Interscreen or Maxwell here. I bought Beattie for $45 on eBay (not that one Iam using), you can get it even cheaper, very cheap with scratches for testing purpose (about $15)... Just do not bid, wait till last 30 seconds and then bid !

Did you find that the one you bought on Ebay to be too cheap? Are you using something else that is better?

Did you find that the one you bought on Ebay to be too cheap? Are you using something else that is better?Yes, I bought all screens at eBay. Its dificult to me, because only bank fees costs me $60. I'am using Maxwell, seems little bit brighter and sharper to me than Beattie. But, Beattie interscreen is good enough. If you want to follow my way, buy one of theese Beatties. They are all plain (no grids) and right now all around $6. I give you an advice : do not bid them now, wait till last minute and then take it.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4688&item=7526571900&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3340&item=7526571905&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=4687&item=7526573151&rd=1
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=3343&item=7526572476&rd=1

There are more Beatties now (more then ten), go for it if you can (and want).

Awesome, thanks for the info. I am going to bid on some of those. I am not too concerned about the price right now, but I will try the 30 second rule.