Cooke Panchro 18mm,25mm issue on Dragon sensor

[Saulius Lukosevicius]

Hello everyone,

I have bought a set of vintage Cooke Speed Panchro S2/S3 lenses rehoused by P+S technic. All lenses have diffferent vintage look. But I have color shifting problems with 18mm and 25mm when using them especially on Dragon sensor. The problem is that magenta/pink vignetting appears. With 18mm and with 25mm. The thing is that we have tested the lens on 4 different cameras, Arri Alexa XT, Red Epic Mysterium-x 4k, Red Dragon 4k, Black Magic Production 4k Camera. Arri alexa and Red epic Mysterium has no color shift at all. But the new Dragon sensor has very obvious color shift. I have tryied to rotate the lens but the pink color appears in the same place with particular camera. On the Black magic 4k production camera the color shift is more visible on the left side. But why then the older Red Epic mysterium x and Red scarlet mysterium performs nice? Why alexa is ok? I mean what was done for the new dragon sensor that it cant work with old panchro lenses? maybe it is something wrong with IR filtration I dont get it. Maybe someone had this problem. Or someone who owns cookes Panchro could answer if they have the same problem on their Dragon sensor. I would appreciate for any useful information.

I attached few examples and comparison.

 

[David W. Jones]

They don't fully cover the larger size sensor.

 

[Ignacio Aguilar]

These lenses were designed with the 35mm Academy format in mind. While they cover a bigger sensor area, what's outside of the Academy area suffers from very severe color shifting, loss of definition, vignetting, etc. These lenses were handmade many years ago, and condition and servicing could also affect their performance from lens to lens.

On Dragon, try 5K HD or 4.5K, as they are very close in sensor area to 35mm Academy, and you'll use the best part of the lens.

 

[Saulius Lukosevicius]

I know how much they can cover, its impossible to use 4k with that colour shift so if you are suggesting to use 4.5k its much worse. As you can see from the photos its full 4k and its not covering without colour shift, if I will use 4k HD then it cuts the sides but not enough and and pink is very very visible. i attached 4k HD photo. And there are no explain why on older sensor everything is allright.

 

[Phil Holland]

The actual issue you are experiencing is what's known as "Smearing" due to the retro-focus design. This is the same issue many people experience when trying to use wider angle Leica-M Mount lenses on modern digital cinema cameras.

Digital sensors in most modern digital cinema cameras "prefer" more telecentric designs because their micro-lenses have been optimized for that. This is one of the many reasons lens manufacturers moved away from retrofocus designs over the years.

Basically the angle of incidences out of the exit pupil is so extreme as you get outside of the center cone of the image circle that your photosites aren't getting filled up evenly. The net result is uneven and colorful field illumination as well as pixel smearing in the field and edges of the image.

 

[Ignacio Aguilar]

We have a couple of PS Technik rehoused Panchros for rent and are 100% fine at 4.5K, and even 5k is OK, but as I said performance from lens to lens may vary a lot.

 

[Saulius Lukosevicius]

So the lens has nothing to do with that. We have tryied to buy another 18mm lens and it performed the same. After a long research with people from red we have found that highlight skin tone OPLF doesnt work with these vintage lenses. And surpsisingly after we tested low light OLPF it looks the same as Red Mysterium x so finally the problem is solved. I am just wondering if using a low light OLPF gives a more blueish image, atleast for me it looks like. However atleast we can use our cooke panchro lenses now..Its just strange that those who want to use these vintage lenses need to buy additional OLPF.

 

[Sidney L. Plaut]

ok i had never seen that one coming - that the OLPF could effect that!

 

[Nick Morrison]

Unexpected, but good to know!

 

[Daniel Soderberg]

Oh wow. That's really good info. I was also confused why coverage seemed so much worse on my Epic dragon than my Epic MX... Thanks for posting about this.
Kind of a bummer though because then if you want to do a shot with a wide Panchro on Dragon with a sun flare, you're gonna end up with the unwanted purple OLPF flare from the low-light one.

 

[John Marchant]

The IR coatings and AR coatings on the OLPF have specific working angles. When the incident angle gets shallow the coatings behave differently.

 

[Steven Abrams]

So the lens has nothing to do with that. We have tryied to buy another 18mm lens and it performed the same. After a long research with people from red we have found that highlight skin tone OPLF doesnt work with these vintage lenses. And surpsisingly after we tested low light OLPF it looks the same as Red Mysterium x so finally the problem is solved.
View attachment 67988

Are you saying this image is the "fixed" one? Because it still clearly has the problem on the right. The sky and buildings are obviously still turning magenta/blue.