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  • 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 :)

Red 23 Landscape

Thanks Andrew.

Those shots made my day and your comments are very instructive.

Emmanuel
 
Yes, it would be to do with colour correction matrix. That's why I need to look at the raw data and see what was actually recorded and analyse from that.

In some cases, it will not be possible to correct all colours without some kind of gamut clipping, in that RED shoots a wider gamut than a general display gamut.

Graeme

jbeale said:
Interesting, I will definitely try that. Would it be correct to guess that the blue channel going to zero in areas of intense greens has to do with "color matrixing" (post-sensor processing) rather than some electronic or physics effect within the sensor itself? Hence, it is a software issue? Is there the possibility to choose our own matrixing function?

Or is this intentional? If the channel goes below the nominal black level of around 50 (in that particular frame) I guess it is, in essence a negative value for that primary. That enables display of what would otherwise be an out-of-gamut color (?)
Click to expand...
 
astro said:
The wide/long shots were shot on 20mm and 180mm at around T-22 with a Pola. The base stop was around T-45 to T-90. I didn't have any more ND handy.
Click to expand...

Thank you for this information! At T-22 you are definitely not going to see the optimum sharpness with this camera or any camera (short of a 8x10" view camera). Diffraction will limit your sharpness at that aperture, regardless of where the lens is focused. With another 3 or 4 stops of ND filter, I have no doubt you would have seen sharper images.
 
Though a 180mm at T-22 shouldn't be a problem.
Wider lenses would behave better about T-11
 
Thanks guy, but I only seem to get a small version..maybe it is a safari thing.
-A
 
Poi Boy said:
Thanks guy, but I only seem to get a small version..maybe it is a safari thing.
-A
Click to expand...

Hmm... I use Safari too (along with 75% of this forum I figure), so I doubt that's it.

They're at the links in his post, not the attachments you see at the bottom.
 
I heard you tried some Cooke S4's and Zeiss Ultraprimes on the RED at Metro Film. What was your impression of the image quality with those vs the STD Zeiss?

Rocketeer said:
We've had a Zeiss STD and Red Zoom on a lightbox and collimator and they are resolving the same resolution(or close enough)

.
Click to expand...
 
Red Guy said:
I think once the EVF gets out there, shots will be in better focus.
Click to expand...

This was shot at F22. I don't think they missed focus... especially on the wide angle stuff. I think it's just that F22 isn't the sharpest spot on most lenses. Also, maybe RED's 18-50 is sharper than the lenses on this test. Possible.
 
astro said:
Though a 180mm at T-22 shouldn't be a problem.
Wider lenses would behave better about T-11
Click to expand...

I am curious why you say the 180mm lens should not loose resolution at such a small aperture. As far as I know, all experimental data indicate that maximum resolution is achieved on real lenses around f/5.6 to f/11. This has been measured with lenses at focal lengths ranging from 12 mm to 400 mm.

Experimental data (MTF measured on lenses for DSLRs): http://www.photozone.de/8Reviews/index.html

Online diffraction-limit calculator:
http://www.cambridgeincolour.com/tutorials/diffraction-photography.htm

Theory: http://scubageek.com/articles/diffraction.pdf
For green light at 560 nm, diffraction-limited lines/mm = 1460/f-stop
(note - regardless of focal length!)

"We can therefore say with some confidence that good 35mm lenses are relatively unaffected by diffraction at f/8 and below, moderately affected at f/11, and diffraction-limited at f/16 and beyond."
http://www.normankoren.com/Tutorials/MTF1A.html

Based on diffraction alone, maximum resolution is always at the wide-open condition. Of course real lenses always have aberations due to non-idealities in materials, geometry etc. which are not so easily calculated, so the theory is more uncertain. At any rate, the experimental data tells the story.
 
Dean Gough said:
I heard you tried some Cooke S4's and Zeiss Ultraprimes on the RED at Metro Film. What was your impression of the image quality with those vs the STD Zeiss?
Click to expand...

The lenses were put on the camera but the testing was very casual. We did some test material of sunlight striking a silver car using a S4 and Renaud felt that the way the S4/Red One handled the highlights coming off the car was very pleasing. Andrew may be able to add more.
 
I have no doubt the research is right.

I've sat through a few lens tests and rushes. Anecdotally most motion picture lenses seem to perform better when you stay off the extremes of the aperture. Longer lenses seem to take stopping down beyond T-11 a little better than wider lenses. Couldn't tell you why though.

I have perhaps over stated the deterioration of the image due to the aperture setting. For instance S4's , Ultra Primes and Master primes perform extremely well throuhout the full aperature range, any deterioration would be subtle. The softness in the images that people are commenting about is, in my view, due to other factors other than lens performance.

Someone else is probably better informed to comment on that.

Andrew.
 
astro said:
I have no doubt the research is right.

I've sat through a few lens tests and rushes. Anecdotally most motion picture lenses seem to perform better when you stay off the extremes of the aperture. Longer lenses seem to take stopping down beyond T-11 a little better than wider lenses. Couldn't tell you why though.

I have perhaps over stated the deterioration of the image due to the aperture setting. For instance S4's , Ultra Primes and Master primes perform extremely well throuhout the full aperature range, any deterioration would be subtle. The softness in the images that people are commenting about is, in my view, due to other factors other than lens performance.

Someone else is probably better informed to comment on that.

Andrew.
Click to expand...

Thanks Andrew,

I actually didn't know about that sweet spot of the lenses included issues with stopping down too far. Why did my focus pullers never tell me that! haha. Good info to have added to the site.
 
dalemccready said:
Thanks Andrew,

I actually didn't know about that sweet spot of the lenses included issues with stopping down too far. Why did my focus pullers never tell me that! haha. Good info to have added to the site.
Click to expand...

Hah! Since when have you ever offered any of your focus pullers T-22 anyway!

There are lot of things you learn in lens tests that are academic. Best practise is often replaced by pragmatism eh!

Regards

Andrew.
 
Struth Blue

Struth Blue

A test shot under very blue NZ daylight with and without 85, 85b and 85c filters would be interesting to see if it had an effect on the blue clipping thingey effect.


Mike Brennan
 
I think this issue should now forever be known technically as "the blue clipping thingey" ;)

...Yeah Andrew, actually I can't remember the last time I was at 22! `Actually it was just the other day when I was operating a film and said to my focus puller, don' worry about the NDs we're just popping up the road and it turned very bright and there I was stopped all the way down. At the time I was cavalier about it (couldn't do anything about it anyhoo) but reading your comment made my stomach churn! haha

I'll have to give you a call and see what you think. I might be back there sooner than I thought.

Oh also Andrw can you kindly inform the forum that every nice spot in NZ was not always a location for LOTR!

Some of them were for The Piano and Xena too! ;)


Dale
 
I would agree that lens theory and lens measurements are not everything you need to know, in practical terms... I agree that normally people want to see the most fine detail in wide shots. Slightly soft long-tele shots still look natural and pleasing, considered as a whole.

But when people are zooming in to 1:1 or even 200% or more on computer screens to analyze things to the nth degree, I believe it's worth pointing out the measurable (if not always noticed) effect of the f-stop setting.
 
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