Alexa Infrared Issues

[Sanjin Jukic]

I do not know what is going with Alexa OLPF/IR but I know what we can get from R1-MX in a real life shooting situations.

Let me show you two examples:

Look at the color of pool water: Shot on R1-MX with Nikon 18-200mm VR, original version @ 200mmm
attached Novoflex/16:9 adapter for Canon EOS on IMS Canon EOS mount,
aperture unknown but it could be something between 16 & 22, Filters: Hoya-Circ-Pola, ND x2, ND x4.
ISO 200, 25 fps, 1/50 shutter.

Look at the color of pool water: Shot on R1-MX with Nikon 18-200mm VR, original version @ 200mm
attached Novoflex/16:9 adapter for Canon EOS on IMS Canon EOS mount,
aperture unknown but it could be something between 16 & 22, Filters: Hoya-Circ-Pola, ND x2.
ISO 200, 25 fps, 1/50 shutter.

You could say there are shots from two different angles on the pool but it is obvious that the color of water

shifted or a changed from greenish to more blueish when I took off one of the ND filters (ND x4),

also the skin tones have got a lighter color...

BTW, the second example has clipped highlights that I saw at EVF but I left it to fix that later in post...

You can download this test at widescreen 1920x800 movie from Vimeo>>>>

 

[Mickey Conway]

Many more issues are brewing up in Hollywood they are renting Alexa from TCH for the new TV series LA Law & Order the AC's told me that 2 out of 14 functions actually kind of work I quote it's a total nightmare. Wish we were working with a friendly digital camera like the RED one.

 

[Gunleik Groven]

San. Thing is that this solution is pretty much unuseable if you want to shoot at a fixed aparture and fixed shutter, thus the IR filters are as neccesary on the R1 as they will be on the Alexa, but a bit less on the MX. Shooting everything @ T 16-22, is pretty much a no-go as a general solution -

 

[Sanjin Jukic]

San. Thing is that this solution is pretty much unuseable if you want to shoot at a fixed aparture and fixed shutter, thus the IR filters are as neccesary on the R1 as they will be on the Alexa, but a bit less on the MX. Shooting everything @ T 16-22, is pretty much a no-go as a general solution -

I wouldn't say like that.

First I didn't take any IR just because the ND mix I used was not so strong (NDx2 + NDx4 = NDx6).

ISO 200, 25 fps, 1/50 shutter.

That was a t magic hour and on bright noon sunlight I would probably need IR but that's also not necessary

if you take aperture between 11, 16 to 22 or 32 if your lens has it.

Busy at the moment but will dig later in my stock photos on the sever to find those shots too.

Stay tuned.

 

[Sanjin Jukic]

Here we go:

All examples have shot between 2 PM and 4 PM at Belvedere Gardens Vienna, end of June 2010.

Shot on R1-MX with Nikon 18-200mm VR, original version
attached Novoflex/16:9 adapter for Canon EOS on IMS Canon EOS mount,
aperture unknown but it could be something between 11, 16 & 22, Filters: Hoya-Circ-Pola, ND x2, ND x4.
ISO 200, 25 fps, 1/50 shutter.

WITHOUT ANY IR FILTER.

 

[Gunleik Groven]

Problem is that many will want to shoot a whole movie - or at least a scene coolgleamA @ a fixed aperture of say 2,8 - (or any other fixed aperture within a lens-series sweet range) because they may not want the the DOF to change from cut to cut, and as they shoot a scene over a whole day, they need to control light with ND's to have the same aperture in the different shots, independently of how the intensity of the light changes over a day.

It's not unusual to stop down the lens 5 stops or more (ND 1.5) on a summerday and NDs pretty much are the way to achieve this.

Single "good" images does not miracolously "solve" the mystery of image continuity...

But of course I agree. you can "take away" the IR problem with aperture/shutter adjustments. You just loose control of the image characteristics as a minor tradeoff...

Thats probably even possible on an Alexa! -

 

[Sanjin Jukic]

2.8 aperture you can use indoors for low or even available light.

The most common aperture are 4, 5.8 or 8 for outdoors with ND/IR combos when you shoot portraits

but when you have landscape or architecture you can easily go down from 11 to 16 to use less NDs

and without IR to avoid all that IR shifting color mess.

That's about my experience.

Have a look again on some of my test examples above shot on R1-MX at a bright sunny daylight situations.

No big shooting philosophy at all, also a lot depends of lens you are using.

 

[Gunleik Groven]

Well, San - you'll find that very often is not true... The aperture is adjusted as to what images and DOF charracteristics the DP wants, not on an indoor/outdoor basis...

At least in my experience.

And of course you can use T11-T22 both indoor and outdoors - when you want deep focus.
Which - as a sidenote - IMHO can be very beautifull.

But allways shooting @ t 11-16 as a guideline, pretty much neglects the flexibility of a larger sensor and 35mm optics, wouldn't you say?

Another problem is that a lot of optics aren't @ their sharpest when you use very high aperture settings...

Anyhow.
Derailing the conversations here. Sorry!
To each his own! Estethics is not an exact science... -

Your images are fine stills!
And if they were shot with MX, the issue would be less.
Good for you!

But even so, I think I can see slight IR differences between your images. F. ex. between the last two with the same lawn and same motive.... But then again, that may be just me. And I'd love to come to Vienna to share a bottle of wine and look at the sceneries with you one day!


Cheers and enjoy Ibiza!

 

[Hans von Sonntag]

The interesting part is that IR pollution on a sunny day can hit you out of the sudden and then never gain. I once got so badly hit that 2 hours of footage were hardcore magenta casted, green leaves brown, black t-shirts purple. That was with ND12 or ND15. Some minutes later all was back to normal.

I then bought a ND hotmirror and use it now and then but I never got struck by IR again whenever we shoot without the hotmirror.

It's easy to reproduce IR pollution with a 5K tungsten fresnel, NDs and black fabricks. Finding obvious IR outside when you are looking for it can be hard - if not impossible. It's unclear to me why you can hit once by IR and years not. I tried to track this down - sun winds for instance - but no astrophysicist could give my a satisfying answer.

Long story short: Sanjin's pictures show the beautiful Vienna but were probably shot when not enough IR was around to pollute the pictures visibly.

Hans

 

[Gunleik Groven]

@ Hans

Yup.

It is pretty unforseeable.
But when it hits, it often hits hard.

 

[Sanjin Jukic]

Long story short: Sanjin's pictures show the beautiful Vienna but were probably shot when not enough IR was around to pollute the pictures visibly.

Hans

Hans,

it was a pretty hot this day in Vienna when those shots were made (more than 30 degrees of Celsius),

actually at these days when the summer big heat started in Europe.

I read that IR pollution also depends much on air temperature.

All what I wanted to say is that MX sensor improved its performance at a hot summer outdoor conditions

that means if you use a higher aperture you wouldn't need to use much of a hot mirror IR filters.

go back to Alexa we would need unbiased scientific side by side MX-Alexa tests to find out which

sensor/camera perform better in a different lighting and temperature outdoor conditions.

 

[Bastiaan Houtkooper]

Sanjin, I see that you are also shooting with a pola filter, first of all it will effect your pool shots more than infrared, secondly you should add it 'as ND6'
Meaning if you have an ND6 and a Pola, you are already blocking 4 stops (more or less) and already critical for IR trouble.
Outdoors I have seen it mostly in fabrics but also a lot in greenery.

 

[Gunleik Groven]

I have seen it a lot in the winter here. I don't think temperature as such is the big issue, diffusion by humidity may make a huge difference on a sunny day, as I have been told the diffusion by the ozone layer may have some effect. These are things that change constantly, and dramtically independently of the wether being "good", "bad", "hot" or "cold".

 

[Sanjin Jukic]

Bastiaan,

mostly I shoot outdoors with a combination of Pola (that has ND 0.3 value) and ND 0.3 or ND 0.6, in extreme high sunny daylight with ND 0.9

and less with ND 1.2 plus Hot Mirror IR filter all of them from Formatt filters that I found the best for me.

Those above particular shots were done with a "cheap" but an excellent Nikon 18-200mm 11x zoom and screw-in Hoya filters (combo of Pola and some NDs).

The back-draw is that you can't shoot in a range from wide 18mm to let's say 20mm-22mm because the more filters you add the more vignetting at wide angle you'll get.