Chromatic Abberation and the M2

Andrew Spirk · June 21, 2007

I can't seem to get any responses to my post at RedRock about this issue, and it's been a huge problem over the past 7 months that I've been struggling to get this to work. Believe it or not, I haven't advanced very far since we first received the M2 in the mail.

I've included a 100% 720p still from our JVC HD-110U.

The focus assist says nearly everything is in focus, yet... you can see it's obviously not. The M2 is attached via the hard-mount, so I can't really explain any reason why it would be mis-aligned and further more, why any part of the image should be blurred. You can also see very obvious Chromatic Aberration, something I hoped to fix by doing one of two things.

1.) Try a prime lens as opposed to a zoom.

2.) Take the footage in via the Blackmagic Decklink HD Extreme card instead of firewire.

Neither did anything to remedy the situation.

Here is a link to a movie showing as I shutoff the M2 and the GG slows down. Keep in mind that I adjusted the focus on the JVC lens very carefully and adjusted the focus-assist to the GG as evenly as possible.

http://www.artofdestroy.co.uk/blog/wp-cont...focus_chart.mov

chuck colburn · June 21, 2007

Andrew,

It looks like your shot is softer on the right than the left side. I would say either you test target was skewed to the film plane or something is tilted in the optical path. If it is a problem with your imaging system that could lead to chromatic errors. And since it is an acroos the field error it might be a spacing of the related optical componets error.

Stephen Williams · June 21, 2007

I can't seem to get any responses to my post at RedRock about this issue, and it's been a huge problem over the past 7 months that I've been struggling to get this to work. Believe it or not, I haven't advanced very far since we first received the M2 in the mail.

I've included a 100% 720p still from our JVC HD-110U.

The focus assist says nearly everything is in focus, yet... you can see it's obviously not. The M2 is attached via the hard-mount, so I can't really explain any reason why it would be mis-aligned and further more, why any part of the image should be blurred. You can also see very obvious Chromatic Aberration, something I hoped to fix by doing one of two things.

1.) Try a prime lens as opposed to a zoom.

2.) Take the footage in via the Blackmagic Decklink HD Extreme card instead of firewire.

Neither did anything to remedy the situation.

Here is a link to a movie showing as I shutoff the M2 and the GG slows down. Keep in mind that I adjusted the focus on the JVC lens very carefully and adjusted the focus-assist to the GG as evenly as possible.

http://www.artofdestroy.co.uk/blog/wp-cont...focus_chart.mov

Hi,

2 questions:-

How does the chart look without the RedRock adapter?

What zoom are you using?

Stephen

Andrew Spirk · June 21, 2007

To answer the questions; without the redrock adaptor the image is all in focus, has no chromatic aberration and is evenly lit.

The zoom setting on the Fujinon is between 20 and 40, closer to 40. The macro and the focus are both turned all the way right.

The lens on the front of the M2 is a Nikon 50mm (1.8), brand new.

Andrew Spirk · June 21, 2007

To answer the questions; without the redrock adaptor the image is all in focus, has no chromatic aberration and is evenly lit.

The zoom setting on the Fujinon is between 20 and 40, closer to 40. The macro and the focus are both turned all the way right.

The lens on the front of the M2 is a Nikon 50mm (1.8), brand new.

And to reply to Chuck-

The angle I am shooting the focus sheet is dead on, this focus issue is persistent with the camera, sometimes less noticeable than others.

The M2 is hard-mounted to the Fujinon, which is why I can't really explain why the focus is the way it is. It's very confusing.

Here are some followup links to previous posts I've made at RedRocks forums, none of which have been solved.

This post ends with me raving about how great the M2 is, it was premature at best. It's an excellent item, but upon closer look at my footage, I still had the same problems.

http://www.redrockmicro.com/forum/viewtopic.php?t=3103

This next post contains images of the setup recently used.

http://www.redrockmicro.com/forum/viewtopic.php?t=3751

chuck colburn · June 21, 2007

Andrew,

I've never used one of those lens adapter thingys..so I might not know of what I speak. lol But what I think I'm seeing is curverture of field. Have you tried focusing on the edges of the target and seeing if the center is then out of focus? Also, (and this is probally a stupid question) does the zoom have to be in macro mode for this to work? If I'm bothering you I'll SFU!

Chuck

Edited June 21, 2007 by chuck colburn

Andrew Spirk · June 21, 2007

Chuck-

At this point, any suggestions at all are greatly appreciated. For the most part, I can't get any real answers from RR or their forums. I was hoping by posting here, I could get some helpful advice, and so far it's headed in the right direction.

The way the RedRock M2 works is relatively simple, and the layout is as follows.

Fujinon Lens -> 82mm to 72mm Step Down Ring -> 55mm Achromatics Lens -> 50mm Hard-Mount Coupling -> M2 -> Nikon 50mm Lens

The M2 has a spinning piece of glass that you focus onto while it is not spinning. Once you get that focus, you start the motor in the M2 and the grain goes away and you can then focus the Nikon lens in front of it. My problem with this is that when I focus on the grain of the Ground Glass inside the M2 box, I can't get a complete across the frame focus, it seems to focus on very few pieces of grain all around.

The focus begins in the center with very dense grain in focus, then as I focus in more, the grain in the center evens out across the frame.

Yes, it has to be in Macro mode, by following the tutorials, asking questions, and the posts at RR, they recommend for the HD110 to turn the focus and the macro all the way to the right, then use the zoom to focus in on the Ground Glass inside the M2.

-Andrew

Edited June 21, 2007 by Andrew Spirk

Andrew Spirk · June 21, 2007

I wish I could edit a post... grrrr.

I miswrote the layout, the correction is as follows:

Fujinon Lens -> 82mm to 72mm Step Down Ring -> 72mm HD Achromatic Lens -> 50mm Hard-Mount Coupling -> M2 -> Nikon 50mm Lens

chuck colburn · June 21, 2007

Andrew,

So the 55mm focal length achro mounted between the zoom and the RR unit is being used as a closeup diopter? Gotta think about this. I find it odd that the zoom is being used for focusing. It looks like it cost some bucks. I would not be pleased with the tech support that you seem to be getting from the RR company. Anyhow if it was sold as a unit that would work with your camera and lens combo something is wonky there. I still think it's an optical spacing problem.

Chris Keth · June 21, 2007

Are you eye focusing or using the lens' marks? Positive that nothign in the system is cross-threaded? Check all of the screws on the RR housing.

chuck colburn · June 21, 2007

Ok, 55mm-72mm whatever, it's in a fixed mount attached to the zoom right? And this is the recommened configuration right?

hmm...if you got the time and just for yucks set you rig up in front of the target and with the camera and zoom with the achro removed, look thru the back of the RR unit and focus the Nikon lens on the ground glass and lock off the tripod. Now put the camera/lens/achro package back on the tripod and see if you can get sharp focus by adjusting the zoom lens with whatever combo of macro/close focusing/zooming settings that work.

Andrew Spirk · June 21, 2007

Chris-

I'll check that tomorrow when I get back into work.

Chuck-

Thanks for those suggestions, I'll give that a shot tomorrow as well and see if anything pops up out of it. I agree it's an optical spacing issue, but every component of this setup is screwed in to one another, so I'm no quite sure what to say about that as it's not really very adjustable.

Brian Valente · June 22, 2007

Andrew

We just returned from Cinegear today to find these posts and the others you left today, so forgive us the few hours to respond. The top-to-bottom hue 'gradient' looks more like interference.

If you rotate the achromat (which I know is a bit tricky if it's completely setup, but just turn it a little bit) does the color banding move as though it's part of the achromat?

If that doesn't change it, try moving things away from the camera (monitor, magnets, anything electro-magnet, etc.) and see if that helps. Perhaps move it into another room?

Cheers

Brian

Brian Valente · June 22, 2007

Andrew -

Coming back from the thread you just opened at Redrock, another poster's experience is that the pink to grey color shifting is due to the JVC's fujinon lens, so please check out his post there too

Thanks

Brian

Andrew Spirk · June 22, 2007

Wow, I feel just terrible Brian! I completely forgot you guys were at Cinegear. My apologizes. I got the email you sent me and just to let everyone on the boards know, RedRock is taking every measure to resolve my situation.

Brian seems to make each problem a customer has his personal mission and is in direct communication with us to remedy our little problem. It really is a fantastic problem, which is probably why I'm so upset about it, once I had it on the camera, I never wanted to take it off again. So it is what it is and I know fully now that RedRock and Brian are going to help me 110%. So without a doubt, my next posts will be shots, rather then tests.

Thanks again to everyone who posted helpful advice.

Phil Rhodes · June 22, 2007

Hi,

It's actually magenta to green and it's at least theoretically a problem on any lens designed to land an image on a 3-chip block. To make it look that bad the poor Fuji must be set up in a very extreme way. Don't get me wrong, it's a very cheap and nasty lens, but it can look a hell of a lot better than that. In fact, I wouldn't be surprised to find that many of the problems with those test images are actually due to some extreme set up (very long focal length, very short focus distance, wide aperture, macro, etc) on the Fuji - and not the adapter at all. That said, one would prefer to see the adapter designed to not require a very extreme setup on the camera's native lens. Pro35, of course, completely obviates the issue by replacing the native lens.

But to be honest much as I like the images from these groundglass adapters in terms of highlight control and smoothness, they do all cause horrible problems in this sort of regard. It's never going to be as good as the bare element.

Phil