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 :)

Cry for help - one-time shoot today spoiled due to mysterious blurring

These Canon lenses- like the 24-105 or the 24-70 -change length while zooming. This lens design tend to get a little bit loose over time. I had once a 24-105 which was tack sharp for about 6-8 month (daily use), then got loose again and had to be serviced by a CPS technician. They could do it easily in 10 min. When the lens was a bit loose there was this kind of unsharpness. (Would explain too why the biggest sharpness in your sample picture is on the bamboo. Tilt effect by loose lens barrels)
The lens barrels are definitely too loose, if they move by themselves while you holding the cam vertical downside.
Sorry Martin if my english is maybe not perfect to explain it perfectly, but I hope you got the idea what I´m talking about. I would check it. If you used this lens for already 500hrs shooting there is a big chance this happened.
I´m still shooting with Canon lenses, but because of the internal movement I prefer to use the 16-35 and the 70-200. They are much more reliable.
Cheers,
Marc
 
If you can all stand my ugly mug on this thread, here's a test I just did while waiting for a client to turn up(!)

Shot on epic with a canon 24-70 2.8L at similar settings to the R3D posted for focal length, aperture, iris, iso etc.... and with me as subject at roughly equivalent distance, with a compression unfriendly detailed backdrop and fairly hot exposure.

150% crops from centre of frame, at RC 3:1 below:
3-1crop.jpg


Then at 6:1
6-1crop.jpg


And at 10:1
10-1crop.jpg


And finally the full frame for reference.

fullframe.jpg


I don't think this is optically terribly different from what the OP found. It does bear out my past experience however that perceived sharpness rather than compression artifacting as such is the main loss as compression increases in Redcode. Scenes like this are tough for the codec, and I do think thats a big part of why the OP's crops look soft.
 
Last edited:
To be honest its worse with a more correct exposure, these are deliberately a little hot to match the OP's shot, and to negate the point that low exposure negatively affects the compression. ( The purely random sensor noise introduced in low-exposed areas of an image is also a compression killer.) That said these are posted at ISO640 and can be rendered as correctly exposed at ISO320 with obviously no change to sharpness.
 
Here's the same shot exposed correctly at ISO 800 and stopped down to f16 for greater DOF. The compression affects sharpness even more in this situation, as the greater DOF gives more optical detail for the codec to sweat over.

150% crops again.

3:1, ISO 800, f16
3-1f16.jpg


6:1, ISO 800, f16
6-1f16.jpg



10:1, ISO 800, f16
10-1f16.jpg
 
John Marchant said:
Here's the same shot exposed correctly at ISO 800 and stopped down to f16 for greater DOF. The compression affects sharpness even more in this situation, as the greater DOF gives more optical detail for the codec to sweat over.............
Click to expand...

Wow! I was totally unaware that there was that big a difference between 3:1 and 6:1 in those types of situations!

Thanks for the examples!!
 
I don't wish to disrespect either the OP, or the fact that this is the Scarlet subforum, but it is worth noting that Epic does more than 5k and high frame rates. It also does cleaner 4K, which can be important in detailed wides like this.
 
At identical settings, EPIC and Scarlet are indeed identical. But Scarlet is limited to 6:1 at full motion 4K, so as illustrated above EPIC offers higher data rates and demonstrably cleaner results in very detailed scenes. Its a specialist scenario however, and no slight on Scarlet's abilities in general.
 
Great stuff guys. Thanks for your help, suggestions and examples.
Can you also post some images from an identical test, using a better lens? Lot of people complain about the 24-70L, so i'd like to see the same shot with a prime!
Were the test pictures shot with the OLPF port bushing installed?


Thanks and kind regards,


Martin
 
Hi Martin, glad my little test was appreciated. I'll dig out a nice prime when I next get a minute. This is with OLPF bush in place. Got to say though, I have NO personal issue with the sharpness of the 24-70 I used on this test. In a complex scene like this I'd suggest the quality is compression and OLPF limited to a certain extent. Goes to show the difference between shooting real life and charts :)
 
Just repeated the shot while consuming my lunch - this is the rather wild grounds of my office by the way...

Nikon 50mm AI-S stopped down to f16, more contrast in the lighting as its now midday, and a slightly crisper lens. Big boy primes are out earning money right now, sorry.

If anything the effect on compression is more dramatic.

3:1 150% crop
nikon3-1.jpg


6:1 150% crop
nikon6-1.jpg


10:1 150% crop
nikon10-1.jpg


and the full frame, to show what a compression buster this scene is:
nikonfullframe.jpg


I promise do crap like this with a pretty girl next time, sorry guys ;)
 
Drew Baird said:
You are correct. WYSIWYG when you are in a 1:1 crop on the sensor. Backfocusing won't help you with this shot, but it would be good to get checked for future gigs.

I have a 24-70L that I rarely use cause it is worthless at apertures higher than f8. I've had back focus checked and my camera is good. If I have to use the 24-70L I will use good ND's to drop the light so that I can get my f-stop into a usable range. It kind of sucks but it is what it is.
Click to expand...

Uh... diffraction is a fact of physics life - it has nothing to do with your individual lens. Lenses vary most at WIDE apertures.

Meanwhile, compression setting may be a factor here as well.
 
Zac C said:
My Canon 24-70 was so soft I had to sell it, but not after I shot a huge gig at 2k. The footage was almost unusable.
Click to expand...

Soem copies are bad and some good. You have to hand-pick your copy
 
John Marchant said:
At identical settings, EPIC and Scarlet are indeed identical. But Scarlet is limited to 6:1 at full motion 4K, so as illustrated above EPIC offers higher data rates and demonstrably cleaner results in very detailed scenes. Its a specialist scenario however, and no slight on Scarlet's abilities in general.
Click to expand...

We have found that even with identical settings, with black shade doen at exactly the same time, our Epic is a touch less noisy than a Scarlet we borrowed for a test. No idea why - different QC tolerances?
 
Could be variance in tolerances I guess Rob. I've got both Scarlet and EPIC in house and they're pretty indistinguishable in my testing. Our third scarlet in the hands of a third party right now often returns noisier footage, but I've usually attributed it to pilot skill... Maybe not though, i guess the analogue nature of the elements that define the noise floor could easily be subject to variation from camera to camera.
 
And yes- don't throw the baby out with the bathwater. 8:1 is fine for most stuff. I guess my point is that even 6:1 can be given a hard time; the slightly hard to master trick is judging whether a scene might give the codec something to chew on.
 
You must log in or register to reply here.
Back
Top