Relay optimal setting?
 

I seem to remember this being discussed here before but I did a search and couldn’t find it, so I’m asking again. If anybody find the thread where it was discussed please feel free to post the link.
I think there’s an aperture range where the P+S relay lens performs best. What is this range? As I remember it is supposed to look softer at wide open (right?), but is there a limitation as to how much it can be stopped down too? Is there a sweet spot? Like maybe 3 or 4? Thanks.

Don't take my word for it but I seem to recall a post here not so long back which suggested 4 as the sweet spot, SLR lenses on front in the range wider than f5.6.

In my far too short period of playings with the "real thing" on a JVC HD100 after about 3 years of evolving a AGUS35, I also found this setting or near to it seemed about best. It also co-incided with what a DP familiar with that particular JVC HD100 had chosen.

You can stop up to the 4, sometimes the 5 setting without affecting the image but typically I use ND filters on the lens to do the actual job and then only use a relay setting of between 0 and 3 to tweak my final image.

Best thing to do is study a monitor for results before hand.

What I suggest is getting yourself a .3 (ND2) and .6 (ND4) filter. These can be used alone or combined to get 3 distinct variations of Neutral Density settings. This is all you will need for most shoots.

Good luck!

Thanks Bob and Dennis.
To be honest I'm more worried about how much I can open it than how much I can close. As you suggested ND filters are a better solution anyways and besides that, shooting with the Mini35 you will find yourself needing more light more often than needing to cut it. Is it true the relay lose sharpness and has other problems when wide open? The best would be to find a sweet spot and light for that. Bob suggested 4, which makes sense since it’s kind of in the middle of the range.
Bad thing is it’s a 3 day shot and I won’t have any time for tests.

The relay lens of the mini35 is quite interesting since most people assume it has the exact same property of a 35mm still lens, thus meaning there must be a "sweet spot" for it. I have found this to be untrue and not nearly the case.

Most people have always assumed the mini35 relay lens is simply a fast 50mm or 24mm lens however if you've taken the time to play with the relay lens like I have, by mounting the relay lens directly to a camera without the mini35 you will find that the relay lens is actually more like a telescopic lens which focuses on an image approximately 7.5 inches (or 18.75 cm) away from the lens element. (The mirrors and prisms account for what seems like a very long optical path but my data is fact, I have measured it.)

Using it as wide open as possible is best in my opinion.

I know for sure that the Mini35's behaviour varies from my own device in this regard and from the Letus35 XL which has a SLR lens for relay. My device and the Letus behave similarly into a HD100.

The Mini35 requires different camcorder ND settings on the JVC to those which work best with my device on the same camera.

That 7.5" is interesting. It falls within the ballpark of the distance needed for a 4+ dioptre plus built-in camcorder lens on a PD150 or Z1P for home-made devices.

When I want the best image in my own device, the 4+ enables me a slightly wider path through my prism arrangement than the 7+ I also use when I want a closer physical coupling for agile work.

P+S refer to the relay lens aperture function as a variable neutral density filter. I have assumed it is an iris arrangement but I did not have the appliance in my hands long enough to look.

(In my own experiments I played around with two polarising filters to see if they would work as a variable ND. They did but there was this dreadful blue colour cast, so I did not perservere in this direction.)

It would be interesting to know if P+S went this route instead of the traditional bladed iris.)

The barrel diameter of the relay lens is surprisingly large, given the 1/3" CCD area it projects onto, so it makes perfect sense that the optical resolution to the widest aperture setting is preserved.

Bob, it has blades. Five of them.


I can swear I have heard people saying the lens doesn't look good wide open. Maybe I’m confused or people have been misled to believe so. I wasn’t sure, reason I asked.

About the distance, I see you use the XL2 kit? It may be different from the HD100 one, but with the HD100 P+S relay I found that it focus within a 6-13cm rage rather than 18.75cm.

It would be great if other Mini35 users could chime in and give their opinions as well. I know Charles Papert has been shooting with one for a long time too.

The relay lens for the XL cams definitely have blades... I can't say for the other connecting kits.

If you've heard people say the lens doesn't look good open they're most likely talking about the "taking" lens, ie. 35mm prime lens not the relay.

As for your relay lens "distance to focus" measurement, you're talking about putting the relay lens directly on the HD100 without the mini35 right? That's interesting that your range was so big... practically 7 cm! Mine was very very fine, within millimeters it seemed but definitely about 18.75cm out from the relay lens.

The HD100 relay too. 5 blades as I said.

No. They were talking about the relay. I think I saw it here actually. In this forum. But I can't find it anymore.

18.75mm or 18.75cm? In your prior post you said cm.
Well, anyway, yes, with the relay lens mounted directly on the HD100 and without the Mini35 I can focus anywhere from 6cm till 13cm away from the front element.

I will try searching the forums for info on stopping down the relay lens, I'm very curious.

From my actual experience using the mini35 with the XL I would honestly say there is no difference. Perhaps the relay lens for the XL and HD100 are very different.. but that would surprise me considering the CCD size is virtually the same.

Did your relay lens have a means to focus? My relay lens had very minute adjustment which would move the taking lens of the relay fractions of a mm. It was so small in fact you could not even see the lens move through the element.

Sorry it was 18.75cm, I made a typo but fixed it.

It might be related to practical issues with mounting, clearances or mechanical strength of a particular structure.

I understand that whilst CCDs are described as 1/3" there can be variations on the active or usable areas of the CCDs which might account for the variation. This would require that for optimum resolution, the widest possible of the available groundglass area would be needed.

This would require small variations of the balance between the groundglass to relay lens v/s relay lens to CCD distances.

I also understand that CCD blocks use an "on-chip" lens. What this is for I have no idea but I suspect it corrects for each colour wavelength for each colour channel.

There would likely be variations on this between manufacturers which would again require the groundglass to relay lens v?s relay lens to CCD distance balance to be adjusted

The "on-chip'" lens maybe allows for the distance light has to travel through the prism to each CCD and maybe some optical adjustment to enable lenses to sit furthur away from the image plane yet achieve wide angles of view. This is a knowing I do not have so I am really only guessing here.

When I set up my own AGUS35 onto the front of the Fujinon standard lens, using the Century +7 I use on the PD150/Z1P version, I found that physically, the groundglass had to be brought closer by about 8mm than my adaptive measurements which adjusted my design had indicated.

The available zone of sharp focus seemed to be slightly smaller for the same zoom setting. In this arrangement, the Fujinon lens, like the inbuilt lens on the Sony cams becomes the relay lens. This arrangement should disqualify any suggestion that there is an optical dfference but someting different seems to be there.

Michael, does your relay lens look similar to this?

http://209.82.46.115/ebay/DSC01024.JPG

Yes, it had a focus ring. As I said, I could focus within a 6cm to 13cm range.


Yes, but it just seems to be slightly shorter.

About the sweet spot, I can swear I have seen people talking about it and many times.

So, did this thread die? None of the other Mini35 users want to add anything? I'm sure there must be more users out there. Let's get some more opinions ;)

This is being confused with the optimal setting for taking lens ie. the 35mm SLR or PL lens.

For the P+S technik relay lens there is no sweet spot because it is a magnifier lens system. Shoot with it completely open.