4.28.2015

The Luminance Conundrum. Why some video might look off.


Engineers know that you can't optimize for everything. Something in the triangle or dodecahedron of choices has to give in order for something more important to spread its wings. The people who design cameras must be plagued with issues like this all the time. Questions like: Do I make the chassis big enough to conduct heat away from the circuitry or do I limit clock speed of processors in order to keep the components cool enough? How many screws do I need to put into the lens mount in order to make sure big lenses don't cause problems? How simple do I have to make the image processing in order to have the camera shoot fast enough for the marketing people? Do I vent for heat or give in to the mania for "weather proofing"? Should the lens be fast or sharp or small? --- I can't have all three.

I've written before about my misgivings concerning the Olympus EM5.2 video but I'm starting to mellow as I dig into the files and come up with some workarounds to the standard shooting set ups. I was frustrated that a camera with some of the prettiest files I've ever seen (as still images) seemed to have issues with detail and sharpness when shooting video. I used the neutral color profile and turned various settings like contrast and saturation down to keep the files from seeming too thick. What I was getting was files with bigger sharpening interfaces that I wanted. It was as if the camera was set to use bigger radius settings in sharpening for video rather than using small radius settings and a higher percentage of sharpening. I wanted the files to be more subtle and more detailed---or at least as detailed as 1080p video files could look. My reference standard is the GH4 but I would be satisfied if the EM5.2 came close. In its standard set-up the files looked as though they were not as well sharpened as they could be and then had a layer of noise reduction over-layed on to them.

I had a little epiphanal insight about the whole mess this week. I was playing around with the camera and switched the profile to monotone (green filter setting) to make some black and white images. The camera went from sharp (in color) to ultrasharp (in monotone). I sat down along a babbling brook to meditate on what might be the deal when it dawned on me that Olympus's engineers must be doing most of their image sharpening in the luminance channel so they could prevent excess noise in the chrominance (color) channels. This would give them good sharpness with low chroma noise when people make images in color and in Jpeg (although I am sure somewhat the same choices are being made in raw).

While they have mastered this technique for still images where there is ample processor time to make everything match up video works in a different way. In the long GOP files noise in color is probably being handled as a median, homogenous setting that requires less speed from the processing engines. And, in fact, when I shoot black and white video, which throws away the chrominance channels I find the video to be sharply detailed and nearly immune from aliasing. Something is happening when the color is applied.

I went back into the menus and made a few changes that helped me produce video files that I am happier with. To wit, I have started using the muted color profile, leaving the saturation and contrast sub controls zero'ed and then bringing down the sharpening to its minimum level. Of course I am using the image stabilization without digital manipulation (mode 2) and I have tried to be very careful not to under or over expose. The final step is to go to the custom curves setting and flatten out the profile just a little bit more; raising the dark part of the curve and lowering the higher tones.

When used this way the camera delivers a flat file that can be messed with in post processing to bring back the contrast and saturation I am looking for. Minimizing the sharpness in the shooting portion of our program is helpful but there is still some sharpening going on. I can live with it.

With the help of these settings the Olympus EM5.2 is quickly becoming my "go-to" camera for any situation that requires me to go "off tripod" and follow something or someone around. It's a great little ENG (electronic news gathering) camera and the constant movement largely masks some of the shortcomings I was seeing earlier in my ownership.

When using the camera in this way I have also found that the best files come from my slower FPS settings. I am happiest with the files (color and sharpening) that I am getting at 24 fps. I would also say that lens selection is helpful. While someone from Olympus suggested that I would get the best quality from their branded lenses it's not really the case. I'm getting my best files (not over sharpened...) with older, legacy Nikon lenses as well as manual focus lenses made for the ancient Olympus half frame series of cameras. These lenses don't seem to have the clinical sharpness of the newest glass but their "rounded" quality and lower contrast seems to help when the camera translates stuff into video. Yes, the newest Olympus glass, like the 75mm f1.8 and the 45mm f1.8 are nifty sharp in still imaging but they are a bit too sharp for video rendering that I prefer.

Every time I get better results I get closer to thinking that the EM5.2 could be the best all around camera on the market today. It's clearly the most fun to shoot with, if it fits in your hands.....

Perhaps the engineers at Olympus decided not to have a separate sharpening protocol for video and depend on the sharpening for full, 16 megapixel files, the result being the over bearing sharpening characteristic when the frames are down sampled to a bit less than 2K for video. I don't know. I've never been a software/firmware guy. But I do know that they understand the issue. Whether or not it's cost effective to fix it is another matter. At this point I am very comfortable shooting good video with these work arounds. I'm glad I spent the time to "zero in" the cameras for the way I want them to look because I think the image stabilization is a big evolutionary step in shooting video.

My favorite rigging is to use the uber-sharp Panasonic 12-35mm f2.8 on the camera, a set of Apple earbuds plugged into the headphone jack on the HLD-8G grip and a small, Azden shotgun mic secured to a tripod socket mounted accessory bar. The camera focuses quickly, the lens renders things in a nice way and the Azden mic is a surprisingly good little shotgun microphone for under $100.

Yes, I have better headphones. Yes, I have better microphones. Yes, I have a fluid head tripod. But the whole idea is to come up with something that is small, light, agile and capable. I think of my rig as the video counterpart to Henri Cartier-Bresson's little screw mount Leicas with collapsable lenses---ready and infinitely available. It's a new age for videographers and these smaller cameras are a bridge between accessibility and ultimate quality. For me it's an engineering compromise I am now ready to say "works for me."  Thanks for reading. 

10 comments:

Frank Grygier said...

There is something magical when a camera begins to meld with it's owner.My attraction to the EM52 increases.

Kirk Tuck said...

I forgot earlier but I must credit my friend, Frank, with the title of this blog post. He has these flashes of genius...

Kepano said...

Curious why you're so intent on making the Oly work for video if you have the GH4 and 12-35mm OIS lens. That combo makes for a very workable handheld rig with video quality that's hard to beat at any price.

Craig Lee said...

Interesting. Does the EM-5II have a way for you to save those settings in a pre-set / user-bank for easier access? Or do you need to remember to manually change from the video setting to the still photograph settings and vice versa?

Kirk Tuck said...

Kepano, Because the image stabilization is like magic. Much better than stabilized lenses on the Panasonic.

Kirk Tuck said...

Craig, I don't know. I'll search through the Byzantine menu and try to decipher that although in the interim I am sure a menu-lover will dive in and educate me...

Michael Matthews said...

Once again, very interesting. How about letting this one live in the ongoing, accessible archive for a couple of years?

It will probably be that long before I can afford an EM5 II. If I'm not too senile by then to remember what video is these technical meanderings may prove useful.

Anonymous said...

Thanks so much for this post. I bought this camera hoping to do a little video work with it then realized it had been over-hyped. Looking forward to trying your settings.

I hope the folks at Olympus learn from it, too. Maybe, they can do some sort of firmware update.

Nigel said...

Just adding my voice to the thanks for this.

If you (or Olympus) come up with a preset as per Craig's request, I'll owe you a beer or three if I ever make it to Texas.

Kepano said...

Kirk, I see some similarities in your work and mine, so I'm keen an how you get on with the EM5.2 for video. I've taken to small chip camcorders with proper XLRs for my walk-and-talk choice (to accompany my GH4 or A7s depending on the job), but since air travel often factors into my gigs, I'm also on a quest to reduce my load.