Welcome to our community

Be a part of something great, join today!

Log in
  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

OLPF "stack" standards

Mark L. Pederson said:
Sure. With a shit ton of artifacts.
Click to expand...

I own both cameras and have the footage two feet away from me at 400% magnification. You can match both cameras and You would not know which is which. Also a 'shit ton' is hardly
a concrete measure, surely You have no access to a side by side comparison.
 
Hmmm

Hmmm

First off, magnifying stills when looking for motion artifacting is not what I would consider a viable methodology.

More to the point, the OLPF is there to control artifacts that only happen in a limited number of circumstances. For instance, if you have a lock off shot with moderate contrast you're likely good with no OLPF unless you get burned by some pattern on a shirt or fence or whatever that just happens to interact weirdly with the sensor pitch or CFA boundaries. OTOH if you are shooting fast moving sports in high contrast lighting, perhaps with rows of seats in the shot kicking specular highlights, then you could get lots of very weird RGB reconstruction anomalies.

I've always referred to Graeme's philosophy in this area as being like a doctor's - first, do no harm. What if you captured an amazing stunt from the perfect angle and the shot had massive aliasing artifacts? How would you feel? There you go.

RED has always taken the long view in this area and I 100% agree with their choice. Even when they were getting blowback from people who judged the image to be a bit soft they resisted dialing back the AA (anti-aliasing) filter. Removing aliasing artifacts after capture is problematic, adding sharpness (or using a scaling filter that holds more high frequency detail by it's inherent nature) after capture is easily accomplished in any number of post tools - including the no cost RedCineX-Pro.

I think of using Bayer pattern color filter arrays for motion as an uphill climb from a physics standpoint and the OLPF as the "crampons" that make that climb possible.

I am willing to wager $1,000 of my own cash that with a sharp, fast, collimated 50mm lens I can produce plenty of aliasing on any shipping BMD camera that lacks an OLPF. All I'll need is a white picket fence in full sun, fairly dark background, open up the iris until there's a little bit of clipping, back off 40-60' until the width of the fence slats in the frame is less than 10 pixels, tilt the camera 15 degrees and pan. Unless you're doing a Timothy Leary biopic I don't think you'd like the rendering ;-)

Cheers - #19
 
Well, I like a man who puts up cash for his belief. I was actually not looking for motion artifacts since I had not come across any in the short time I had the camera. I was merely looking at the resolution, latitude and noise
to see if I could match both cameras to inter cut, and I believe one can rather well, in spite of the resolution difference. However, I did discover that with the same lens the Red had more CA than the BMC and I could only attribute that to the OLPF. Considering Your Picket fence scenario, with the BMC they would at least stay straight, but I will look for a similar condition and do a side by side. Last note on sharpening, Red Cine produces
completely unsatisfactory results. It is easier to raise the noise reduction on the BMC and blow it up 130% to match the look. I just reviewed a few shots I did of blowing leaves of oleander in strong wind with partial
back light and truly, I think it is as clean as I would ever want it to be, but I will search for those motion artifacts if they are there.
 
I've done extensive shooting with my epic which has no optical low pass, and I've only rarely come across artifacting. The sharpness gained is extraordinary.
In theory you'd think it would be more problematic but in real life it just isnt.
 
Short of a picket fence, I allowed myself to pan across the dense mesh of a back lit Miller Aeron Chair with both Cameras, same 150mm lens, same resolution UHD, but Prores with the BMC and no noise reduction. I paned at a speed which created the worst moire on the monitor. I can not see any difference or any motion artifacts with the BMC compared to the Epic. Les' idea of ripping the OLPF out of the Epic becomes increasingly attractive. Maybe the Dragon Owners should give it a try since they are in a tiffy about that. Anyway Blair, like You said the circumstances may be rare or hard to produce, I would put the grand towards the BMC. Its still a good value for a few month until everybody jumps on the alphas or whatever the next digital miracle is promised.
 
Rolf Kestermann said:
I think the days of the OLPF are numbered anyway. BMC 4k is as sharp as Epic 5K, Nikon is getting rid of theirs, any piece of glass behind a wide angle in the days of film was a no no, (nylons were OK), like any glass
in front of a tele past 100mm(unless designed for it). Also, not sure how a 'telecentric" lens design would help, It produces an orthographic picture which is useless for motion picture.
Click to expand...

Talking is nonsense.Share some footage side by side.Thank god i did my tests and shot with BMC 4K and its shitty compared to Epic.
 
Not to be overly pedantic but one rationale for having a stronger OLPF is because moire, or lack of same, on any particular monitor you might be looking at is not definitive proof - especially if you are not doing a full res decode. This is primarily due to the how the pitch of a particular panel can cause wave cancellation or wave resonance based on the frequency of high contrast details and a few other factors too geeky even for me ;-)

BTW Rolf, I wouldn't be so sure the OLPF is the reason you saw more CA on Epic than the BMD as the different sized sensors utilize more/or less of the outer portion of the lens elements where CA is more common on most designs. In any case, if you're getting results from the BlackMagic cameras that suit your goals it really doesn't matter what I think or what the physics are. Go forth and create!

Cheers - #19
 
I can see now how these threads drag out, but I guess there is always some fun and some info in it. I really think that You approached a very important subject matter and I stumbled upon it as I was comparing opposing designs. I actually returned my Epic on suspicion that the OLPF was not planar with the sensor based on CA results I was getting by rotating the lenses in their mounts. I am very pragmatic in the choice of my tools and have no brand loyalty, 90% of my work is with the Alexa, not because it looks better, but it has the best viewfinder and it isn't glitchy. The BMC turned out to be a great surprise for the value, full version of Resolve, global shutter, common SSD drives. Honestly, to avoid its qualities of size, picture quality and value simply because of brand loyalty is just a foolish way to limit ones art. This is not directed at You Blair but the "shit language" crowd that always seems to know better. More specific, concerning the CA between the cameras, in UHD mode for both the coverage is very close to identical. As one can see on my post count I am not a pro in this field and I could upload samples of simple shots but don't know how to reduce them to the size that seems to be required, any help would be very much appreciated.
 
Rolf, you can put pictures somewhere like dropbox, then you hit the button when posting that looks like a little movie screen and enter the internet URL in there.
 
I think there's some misunderstanding here of the implications of this article. Extra stack thickness a lens wasn't designed for did not (or did not only) move the point of focus - it degraded performance AT that point of focus. This isn't simply a matter of re-collimating or ignoring focus marks.
 
Good point Lee. The optical theory gets deep pretty quick in this area. I agree with your note about performance metrics beyond focus, starting with the MTF curve, that are impacted by the interdependent physics involved.

Cheers - #19
 
So I put a bunch of folders together which contain an After Effects project with corresponding source frames of the two Cameras. I have to recant on my suspicion that the OLPF introduces
CA, since I could not reproduce it in the follow up shots. I have more details in a general note and than specific ones in the different folders. This is the URL to access these files:
https://www.dropbox.com/sh/g3mruzs11vp0i92/AADIF9B3jX3ghzeWRCVQgtcta
 
You must log in or register to reply here.
Back
Top