Olympus OMD -E-1 Moire Problem

[Speedy]

I just acquired the OMD E-1 and on the first shot of about 1100 photos shooting raw and Jpeg (Large) I noted the disappointing appearance of moire in a few of the files, e.g. not only in patterned clothing but also on the sides of buildings.  It seems to be less evident or not at all in the Oly Jpeg files but very evident in raw.  Has anyone got an easy workaround for the RAW files for this.  (I am aware of a few methods on the internet for Moire generally).  This is disappointing in that I have not seen or been troubled by moire since early digital cameras back in 20001-2 era, and certainly had not seen this reported in any write-ups on the camera, or I likely would not have switched from my OMD E-5.

Speedy in BC

[Telecaster]

Moiré is a consequence of having no anti-aliasing filter in front of the sensor. I can't say I've noticed much objectionable moiré with the E-M1 but it does show up from time to time. Same with Panasonic's GX7 and most certainly with Sony's A7r. There's so special trick to dealing with it in this case. I tend to go for selective desaturation rather than spatial blurring, but it depends. Stopping down into the diffraction zone can do the job when deep DOF is desired.

-Dave-

[ErikKaffehr]

Hi,

It may be argued that a specially designed OLP filter is probably less destructive to image quality than stopping down.

Check this: http://blog.kasson.com/?p=5073

Best regards
Erik

Moiré is a consequence of having no anti-aliasing filter in front of the sensor. I can't say I've noticed much objectionable moiré with the E-M1 but it does show up from time to time. Same with Panasonic's GX7 and most certainly with Sony's A7r. There's so special trick to dealing with it in this case. I tend to go for selective desaturation rather than spatial blurring, but it depends. Stopping down into the diffraction zone can do the job when deep DOF is desired.

-Dave-

[Speedy]

Dave,
Thanks for your reply.  I understand what you mean by selective desaturation, but am not clear how you might use this technique to correct moire?  Also when you say stopping down into the diffraction zone is not clear to me.  May I trouble you for further elaboration?
Thanks very much.

Speedy in BC

[GLJ]

If you shoot with a camera without an AA filter, you will run into these problems on regular or man made patterns.
There have been many web based tutorials out there over the years - often by wedding or fashion/product/clothing image professionals that have had to deal with the problem in the past (and now its coming around again!)
Try doing a google on "removing moire". Bound to be loads of videos etc out there.

[Telecaster]

Thanks for your reply. I understand what you mean by selective desaturation, but am not clear how you might use this technique to correct moire? Also when you say stopping down into the diffraction zone is not clear to me. May I trouble you for further elaboration?
Thanks very much.

Well, I'm not correcting moiré per se by desaturating...just hiding it. It only works in some instances, like small areas in a photo where the moiré pattern can be hidden by reducing the intensity of its colors. As for diffraction...stop a lens down far enough and you can reduce its resolving capability to the point where moiré (mostly) goes away. Not my #1 recommendation in most cases but it does work. As GLJ says there's lots of info around on various aliasing reduction techniques.

-Dave-

[ErikKaffehr]

Hi,

Most raw processors have options to reduce moiré and those can be quite effective on colour moiré. Those filters are strong medicine, so they are best applied locally.

It may also be that some raw processors produce less moiré than others. In my case I have a camera producing a decent amount of moiré and it seems that Capture One is better at handling it than Lightroom 5.3, which is the program I normally use. There is an open source program called RawTherapee which has an advanced method for reducing colour aliasing, you could try that one, too.

Stopping down can eliminate Moiré but at significant loss of resolution. The images below are from a camera with big 6.8 my pixels and no OLP filtering, and it takes stopping down to f/16 to eliminate moiré. With your 4/3 sensor you would need to stop down far less.




The images above come from this article: http://echophoto.dnsalias.net/ekr/index.php/photoarticles/78-aliasing-and-supersampling-why-small-pixels-are-good

Best regards
Erik

Well, I'm not correcting moiré per se by desaturating...just hiding it. It only works in some instances, like small areas in a photo where the moiré pattern can be hidden by reducing the intensity of its colors. As for diffraction...stop a lens down far enough and you can reduce its resolving capability to the point where moiré (mostly) goes away. Not my #1 recommendation in most cases but it does work. As GLJ says there's lots of info around on various aliasing reduction techniques.

-Dave-

[Speedy]

Dave & Erik,
Got it!! Both your responses were very helpful in understanding the issue and correcting same.  Much obliged.

Speedy