Chromatic aberration
 

Does anyone know how to get rid of it? Im using an iscorama 54 anamorphic adapter on an EX-1 and noticing a degree of colour fringing sometimes that just doesn't happen on the EX-1s amazing lens. Just wondered if anyone knew of a program to get rid of this?

Iscorama 54 huh? So you're shooting 2.66:1 movies. Great! The punch of that is probably worth having some fringing on board.

Agree Tom!

Mark,

It depends on the type of aberration. You might be able to run the footage through after effects and scale the RGB channels differently if it's a simple type of fringing. Other things you can do is to key the fringe colours and desaturate them, sometimes this can work, it really depends on the type of footage.

I'd love to see a frame. What's the resolution like through that adaptor?

cheers
paul

Hi Paul

This is without the anamorph

http://www.freewebs.com/markwilliams/without.png

And this is with

http://www.freewebs.com/markwilliams/Anamorph.png

Oh dear - I see what you mean. Almost better to mask down the original frame rather than have to accept wooshy edges like that.

I was about to say something similar. i thought the lens would give you a much wider fov. In this case you'd get better results cropping the original down as Tom says.

Is the adaptor meant for 4:3 cameras perhaps?

Having said that you could squeeze the channels horizontally (try expanding the red a little bit widthwise, 100.25%), i think it would clear it up a bit. Or run it through a photographic (RAW converter) style defringer.

cheers
paul

VirtualDub has a free CA correction filter. Do a search.

Bill I was just thinking about you! I was using your picture profile when I took it. This is with Picture profiles off

http://www.freewebs.com/markwilliams...20pp%20off.png

Err, having looked at the pictures; don´t really know which way to take this. Better without?

Mika I would say no difference with PP on or off. I just thought people might like to see nd judge for themselvves. Bill I've found the plugin and downloaded virtual dub. Imported the picture and added the filter. However I cant see the effect in the preview screen? When I do get a preview screen its zoomed in so much cant see a lot?

I would guess though whatever I do Im not going to get rid of this! Im surprised virtual dub has a tool like this and after effects doesn't.

I wonder if I moved the iscorama forward a bit? I'll try that tommorow.

I guess you could get away with it quite simply by forgetting about the anamorphic adaptor, having framing guidelines in your monitor/viewfinder and cropping afterwards. I don´t know if it´s possible to define a box cursor to the ex, hardly so.

The PP settings won't be the cause of CA.(doncha just love acronyms?)
But, my question to you is what aperture settings did you use on the shot with and without CA. CA, in hi quality optics, is made worse by long zooms and apertures too far from the sweet spot. If you were shooting down around f/8 or less, this would be my guess. Also, how does the adapter mount to the cam lens? If it's tilted, even slightly, relative to the lens axis, you could induce CA.

Mark, I assume you moved the camera between takes, as the anamorphic is in reality a 0.5x wide-angle converter but in the horizontal plane only, and your pictures don't show this.

Also the Iscorama has a focus ability does it not? Are you leaving the Fujinon at infinity and focusing with the A lens?

tom.

Hi Bill. No the aperture was wide open.

The adapter screws on although the adapter is heavy 1k I thought it should be fine for a quick test. Do you think it would make a difference if I used a support?

Hi Tom. Yes I did move it and it is different. So not a fair test. Although more pictures show the same difference. I could set this whole thing up with a tripod and support if you think its worth it. Yes I am focusing with the A and my EX-1 is set to just before infinity.

How I did this was took a snap from the vegas timeline after reseting the properties pixel aspect ratio to 1, 4568 not quite 1.5

The camera is now on a tripod with the A supported. The lens is set to infinity and the A is set for two metres Its minimum setting. The distance is about 6 and a half feet which the A is limited to 5 feet so this might be a problem? This is with the shutter off and the aperture fully open. The picture was taken in vegas 8 with properties set for widescreen and media properties set the same. The frame and comp were an exact match.

http://www.freewebs.com/markwilliams...%20OFF%201.png

Any questions or any more ideas! Im running out of them.

I've suddenly thought of this. I use a Bolex Aspheron (designed for 16 mm cameras) as a wide-angle converter for my camcorders. It works beautifully on anything from the TRV900, through VX2000 and now my current Z1. But when I borrowed an EX1 for a week I found there was no way I could get a sharp image using this lens, and it made me think that maybe the Fujinon's internal design doesn't lend itself well to add-ons. Could this be a contributory factor do you think?

I think you need to tripod the combo and connect the ouput up to a nice 1920 TV. Of course you'll be seeing horizontally compressed images, but you'll also have time to play with the focus settings (Fujinon and A) and the apertures to see if things clean up at all when stopped down. Abnd is that pincushion distortion I see on the LH edge?

tom.

Tom I think you may be on to something. And yes the side of the TV is warping much more than it should. Something is not right with this picture! I don't yet have a 1920 monitor just a HD ready one. I'll connect that up tomorrow and report back. I wonder if others are having problems adding lenses?

Sony sells a wide angle adapter just for the EX1. Has anyone used this successfully?

I am about to buy an EX1 and accessories, and I have included the Sony one in my purchase list.

Thanks, Scott K.

They certainly are. There are posts on this site about the new Century w/a converter being a big disappointment at the edges - just like yours.

Tom just checked my firmware version V1.02_0337 Do you think the fault may be with the camera?

I don't think you can lay blame at Sony's door if the Fujinon on its own is good at all focal lengths and all apertures and then you go and fit another's aftermarket optic. Sony's w/a is a feeble 0.8x, which may or may not tell you something.

Yes I agree with that The camera alone works fine. But I want to know its limitations and to know if they can be overcome. Letus had to make a corrective lens for the EX-1. I wonder if this could be where my problem lies?

I didn't realise the camera was moved with those first shots, hence the question about why the adaptor one was not wider.

Having said that what is the camera actually recording. If you are at 1920 x 1080p and you put the adaptor on and you get a 1920x1080p anamorphic image, right? But aren't anamorphic ratios usually designed for less wide sensors (4:3 usually, right?). So you're going to get a huge squeeze on a 16:9 sensor assuming it covers the entire image?

If you're getting weird distortions through the lens you could always create a warp layer in AE or something similar to unwarp the image because the warp would probably the same all the time. Long winded and a complete pain, but possible

Just curious...

cheers
paul

Paul after reading your post I had a thought and just put a straight line against the TV.. Its not straight. I dont think there is distortion here at all now especially when everything else is straight. Look at the VHS opening near the bottom. That problem is now solved! Just the edge colours now. What do people think? Is the colour bleed such big problem that it would be noticeable on a large screen?

I think that's to be expected. It could be the result of sending the squeezed image through a prism, or it may be the nature of the adapter. I think any reasonably priced anamorphic is going to have trouble with CA. I've never used the iscorama 54 before, but I have done a few jobs with Panavision anamorphics. How does it mount to the camera? The compression is very sensitive to vertical alignment, so perhaps if the lens if rotated just slightly that could cause similar problems to what you're seeing.

The Adapter screws in and I had it supported. It can be rotated and I did it by eye There is a white line on the camera to help.. I had the lens on and off a few times I dont think its that.

Sean do you think it would be noticeable on a 40' screen?

Yes. It's visible on a 17" monitor. The question of whether or not it is objectionable is an aesthetic question, and depends on many factors. I really do think it's inherent in the design, and that will happen with any affordable anamorphic converter. The iscorama also basically has a variable distance proxar as a focusing element, which may cause some aberration as well as not being designed for digital use, especially HD.

OK so using it with my EX-1 is going to leave visible and in my opinion unpleasant artifacts. But I could use it with my standard 16mm camera to achieve a widescreen look? Probably free from this problem.

Paul - an anamorphic lens is a wide-angle converter but in one plane only, and isn't designed for any particular aspect ratio gate or chip. Turning it off the normal horizontal axis won't affect the CA in the slightest.

Mark - you ask if the colour bleed is such big problem that it would be noticeable on a large screen. The answer has to be yes if your films are yawn-a-mile boring, but no for any other production. If your clients are reduced to looking at the frame corners and whispering to their neighbours that resolution is down somewhat and vignetting is beginning to be a problem, then you've lost it as a filmmaker.

I'm pretty sure you're not amongst this group, so don't lose sleep over the edge definition. It's like that with my Aspheron on the Z1. It takes that lens's wide-angle equivalent of 32 mm down to a visually striking 17 mm, and with zero barrel distortion that's a strikingly powerful focal length.

There are losses to be had, for sure. But the gains in dof and perspective distortion control far outweigh the technical losses, I assure you.

tom.

Tom Thank you. One more thing How in your opinion and if at all would this aberration affect chroma keying? and other FX work!

Good question. I'd say 'adversely'.

I have tried to use the letus with a pentax lens and then the Anamorphic adapter. I cant seem to get good focus with this arrangement do you think if I bought the EX-1 Letus updated lens it may solve all problems? including the colour bleed?

You asking me Mark? The answer is I don't know, and no-one will know till they test it scientifically and carefully.

Thing is, anything you fit in front of your front element will degrade the image. From a UV filter to a wide-converter to an anamorphic to a grad to a Letus to a spinning disc to a prism, microscope, monocular of the double-glazed bus windows.

But if all or any of these things enable us to get the shot, then the loss of resolution has been worth it. Oh yes. It's a bit like Mercalli image stabilisation - you lose resolution but gain screen-cred.

tom.

Tom Yes I agree. Would need to do tests. But possibly more money that may go nowwhere. Its my Birthday today and I have some cash. Choices? I have an old adobe premier I could upgrade to get the old serious magics On location program. Buy a cheap jib OR go for Hiens EX-1 achromat upgrade. Some have said Hiens new achromat loses more light? Swings and roundabouts? I think the likeliehood is Im not going to get rid of the chromatic aberration and just stick with it as is. Do I need to gain a little extra sharpness with Hiens new lens at the expense of light? As for the cheap jib? On location could be looking good!.

That sounds like a lot of glass involved, which is going to create lots of problems with maximum sharpness, and using a letus will never be as sharp as just the stock lens (that's one thing I like about it so much). I don't think you're going to get anamorphic without some kind of CA or other degradation for less than $100k, so follow Tom's advice and go for something that's going to really improve your shots.

Sean my thinking was not about sharpness so much as the chromatic aberration