25mm RPP Distortion

[Tom Gleeson]

Used a set of RPP the other day for the first time on a TVC and was very happy with performance overall except for the 25mm lens which had a pronounced geometric distortion. I had a shot where the focus was set at about a meter and in the BG was a bench top about 3 meters away. I was suprised to see a curvature (bowing) to the straight bench top and to the ceiling.

I was under fire with alot of shots to get through so could not test this further nor can I post an image as the TVC has not been to air. Has anyone else seen this distortion? I need to test further but its a bit disappointing if a only a moderate wide lens such as a 25mm has as much distortion in it as I saw.

 

[Andrew McCarrick]

Used a set of RPP the other day for the first time on a TVC and was very happy with performance overall except for the 25mm lens which had a pronounced geometric distortion. I had a shot where the focus was set at about a meter and in the BG was a bench top about 3 meters away. I was suprised to see a curvature (bowing) to the straight bench top and to the ceiling.

I was under fire with alot of shots to get through so could not test this further nor can I post an image as the TVC has not been to air. Has anyone else seen this distortion? I need to test further but its a bit disappointing if a only a moderate wide lens such as a 25mm has as much distortion in it as I saw.

Could this be part of the problem with the 18mm taking so long?

 

[Roberto Lequeux]

I thought RPPs had close to no distortion at all. Could you have a bad sample?

 

[Pawel Achtel]

Tom,

Wide angle lenses at close focus are notoriously difficult to design without some level of barrel distortion. You have three choices: either increase the focal length and the distance for the same magnification (you will have less of the background, though), fix it in post or use Master Primes.

 

[Roberto Lequeux]

Yea, thanks for bringing that up. If you get close on a wide you can't do anything about it. Physics, right Pawel?

If that is the case Tom please let us know. Thank you.

 

[Tom Gleeson]

RPP distortion?

RPP distortion?

I am going to the grade on Thursday and the TVC is going to air on Monday so I will come back and post the image then. As I pointed out in the original post I need to be more scientific which I will be as soon as I get some time to do a proper test. Luckily very busy at the moment.

 

[Sanjin Jukic]

Tom,

Wide angle lenses at close focus are notoriously difficult to design without some level of barrel distortion. You have three choices: either increase the focal length and the distance for the same magnification (you will have less of the background, though), fix it in post or use Master Primes.

You don't need Master Primes especially if you can't afford it for many reasons.

Simply get RED1 with Birger with a quality made Leica-R adaptor and then you can get the picture at close distance without any curved lines in a background.

Have a look at the pictures below.

Shot on RED1 with Leica-R 19mm f/2.8 @ f4, IMS mount, distance to the focused (Genelec loudspeaker) object 1m.

Shot on RED1 with Leica-R 24mm f/2.8 @ f4, IMS mount, distance to the focused object (Genelec loudspeaker) 1m.

Shot on RED1 with Leica-R 24mm f/2.8 @ f4, IMS mount, distance to the focused object (Genelec loudspeaker) 0.5m/50cm.

 

[Roberto Lequeux]

I am going to the grade on Thursday and the TVC is going to air on Monday so I will come back and post the image then. As I pointed out in the original post I need to be more scientific which I will be as soon as I get some time to do a proper test. Luckily very busy at the moment.

Thanks. Till then, about how far were you from the subject?

 

[Pawel Achtel]

You don't need Master Primes especially if you can't afford it for many reasons.

Simply get RED1 with Birger with a quality made Leica-R adaptor and then you can get the picture at close distance without any curved lines in a background.

Have a look at the pictures below.

Sanjin, Leicas are good, but I think changing a PL mount to Birger or using still lenses on the kind of jobs that Tom does would not be the most efficient way. It is a lot cheaper to rent a wide Master Prime or even PL mount Leica for a day. Barrel distortion is also easy to fix in post.

 

[Sanjin Jukic]

Sanjin, Leicas are good, but I think changing a PL mount to Birger or using still lenses on the kind of jobs that Tom does would not be the most efficient way. It is a lot cheaper to rent a wide Master Prime or even PL mount Leica for a day. Barrel distortion is also easy to fix in post.

Pawel,

you are right.

BTW, my RED concept considers the following parameters: lightweight, best still lenses, hand-held shooting always as a first option, low profile crew, low budget projects...one day a big earnings from all of that...

 

[Aaron Bernakevitch]

I have noticed the distortion as well. Just got off the phone with red and the tech had said that should not be a characteristic of the lens. He had advised me to send in mine in for further testing. I really love the lens's with their clarity, contrast and fall off. Just need to get a fix on this distortion.

 

[Jeff Kilgroe]

I thought RPPs had close to no distortion at all. Could you have a bad sample?

The distortion on the 25mm RPP is not bad at all, it's a close focus + wide angle issue. As Pawel points out, you can always shoot with master primes and even they are not "distortion free" at the wide end of the spectrum when in close proximity to a subject. But they're as good as it gets. Some of the newer designs from Nikon and Canon and other more widely produced lenses are quite good for this too. You want distortion, you should see the 35mm Mamiya AFD 645 prime. It wouldn't show that much distortion on a 35mm camera, but when shot on medium format, it's almost magical in a way. Hehehe...

I'm quite pleased with the RPP's at their price point. And IMO they perform every bit as good as Ultra Primes and S4's, in some ways better, in some ways not quite as good. Some differences of course and each type of lens has its own strengths and weaknesses.

If you guys are seeing extreme distortion with the 25mm RPP, perhaps you should post an image. I suppose there could be some lenses with a distortion problem. Mine handles as expected... but no lens is 100%, just keep that in mind.

 

[Disco Legend Zeke]

I recall a "FLAT FIELD" lens from Nikon. You payed a lot extra for the feature. A better solution today is fix it in post by "un distorting the image" digitally in timing.

Because this is a software fix, unlike an optical solution, the design (programming cost) would be steep, but once programmed, all owners of a particular lens could use it.

In another thread, i suggest post processing as a fix for judder problems.

 

[Stephen Williams]

I recall a "FLAT FIELD" lens from Nikon. You payed a lot extra for the feature. A better solution today is fix it in post by "un distorting the image" digitally in timing.

Because this is a software fix, unlike an optical solution, the design (programming cost) would be steep, but once programmed, all owners of a particular lens could use it.

In another thread, i suggest post processing as a fix for judder problems.

I am looking forward to seeing the first distortion test of the new Cooke Pancros, not a fan of distortion from lenses & cmos sensors myself, but probably the new cool.

 

[Dan Hudgins]

Software

Software

I am working on some software to correct lens aberrations, barrel, pin cushion, chromatic, coma (softness at the edges of the image), vignetting, etc.

Its part of the de-Bayer software I am working on for true RAW Digital Cinema Cameras you need the aberration corrections for C/CS/D mount lenses since many of those are not quite what one would like as is.

I do plan if I can work it in to have RGB-to-RGB processing, so if all goes well those aberration corrections could process 4K TIF to 4K TIF rather than just RAW-to-TIF, that way you could process your RED ONE footage through the filters to remove most or at least some of the distortions.

I am sure there must be some other programs that can process TIF files as well, so you should be able to use them in Batch mode?

After you filter the images from various good lenses for equal sharpness, distortion mitigation, and Chromaic issues the results would look more or less the same, even flare and yellow cast can be leveled with the clip points and gammas in the color correction steps. Many of the point an shoot cameras use image processing to get impressive results from so-so zoom lenses.

Image processing for lens aberrations should be built into REDCINE and REDALERT etc. since with Scarlet coming people will need to deal more with lens aberrations from C mount lenses and other types.

 

[Disco Legend Zeke]

... Many of the point an shoot cameras use image processing to get impressive results from so-so zoom lenses.
...

When color cameras changed from tubes to chips, we found that we were correcting a lot of lens problems electronically in the camera registration process. In my patent, we pre distort the image, and the cheap prism glasses un-distort it. The Really groovy (oops showing my age) thing about the so-called LeaVision patent, and the 30 or so derivitave patents is that they are all (IMHO) public domain, and prior art.

I am really excited to see work is well under way to make generic barrel and chroma correction software. It's the kind of add in i would pay 50 bucks at fry's for, or better yet directly to you. That 4 inch wide 12 MM lens in your magnifying glass prolly has boukou boka.

Feature request ...please... judder correction. Since judder correction is done in hardware on high end monitors, we know it works, adding frame straightening to our timing controls just make sure there is a version for Sony Vegas. Thanks.

 

[Dan Hudgins]

Judder?

Judder?

Feature request ...please... judder correction. Since judder correction is done in hardware on high end monitors, we know it works, adding frame straightening to our timing controls

It seems Samsung has fixed that problem but in hardware,

http://samsungplasmatvfaq.com/index.php/Judder

But you probably need to adjust the display field rate to get it out, so that would not work for normal field rate displays?

Does anyone know of software for lens aberration corrections that is freeware or otherwise that is out now?

 

[Andrew Wilding]

Adobe Raw has tools to fight abberations, but only for stills. The tool for CA is hit and miss but eliminating pin-cushioning and vignetting works a treat.

 

[Dan Hudgins]

Batch TIF

Batch TIF

Adobe Raw has tools to fight abberations, but only for stills. The tool for CA is hit and miss but eliminating pin-cushioning and vignetting works a treat.

Can it Batch process TIF files?

If so then would it work if you export your R3D as a set of TIF frames?

 

[Yoji Nishimura]

hi sanjin(三人?)
I like Genelec of monitor speaker. I use too.