16mm 500fps: Testing a Photo-sonics Actionmaster 500 in august 2024 (with test footage)

[Jefta Varwijk]

I did a PAM500 test and thought I'd share it with the hive-mind. Not an expert. I'm the guy headbanging.

It looks pretty good except at 500FPS where it loses too much sharpess. working on fixing that. (if anyone has experience...)

Shot on fresh(ish) 500T 2R (bought may 2024 at BHphotovideo)

1 (unbalanced) mag was CLA'd by myself. Did not lube the gate itself except with my greasy fingers.

Camera movement was tested at all speeds. sounded good.

Powered by 2 sequenced 5500mah 14.4v Lipo batteries

Camera was on a heavy tripod with a plate and 1 3/8 screw.

no ND

Canon 8-64mm T2.8 (colimater-tested mid-july)

Cameragate also tested and found sharp on colimater (but a tad bloomy at wide)

[Mark Dunn]

At 500pps it's sharp at first but jumps out after about 5 seconds, so about 120 frames or 3 feet. I wonder if the film on the supply spool is getting a bit loose and then snatching tight and moving the gate out. I may be talking rubbish but it won't hurt to check.

At the same point the shutter timing goes out as there is a bit of smearing (look at the white patch on the chart). It pops back at about 2:35 and the sharpness improves. I would be checking for dirt and film residue, especially around the gate.

[Jefta Varwijk]

Hi mark, thanks for your pointers. The 500fps is a problem still indeed, I'm attacking it from multiple angles. I cannot get a hold of original photo-sonics mechanics, the only one who responded is the president of the company, and he referred me to people who I was already in contact with!

Right now it seems that the mag and sprockets are not perfectly aligned, and the magazine will require some tuning. The magazine and film movement is very rigid, works very differently then the 16mm mags i know. It seems that a part of the loop, after having gone through the gate, is pulling on the film a bit, thus pulling it away from the perfect focal plane because of centrifugal forces on the film at 500fps. I'm not 100% confident that can be fixed with the magazine I have, since I have a earlier 'non-balanced' magazine.

[Mark Dunn]

What you need is a high-speed camera to analyse the film travel lol. Perhaps you can set something up with mirrors.

[Robert Houllahan]

Here is a shot I am pretty proud of that I did with mine a few years back.

I have to rescan this as the Xena scanner I scanned it on was in between some software updates and the GPU perf stabilization is not perfect.

I had the PhotoSonics camera set to 460FPS for this.

Edited August 23, 2024 by Robert Houllahan

[Jefta Varwijk]

On 8/13/2024 at 11:56 AM, Mark Dunn said:

At 500pps it's sharp at first but jumps out after about 5 seconds, so about 120 frames or 3 feet. I wonder if the film on the supply spool is getting a bit loose and then snatching tight and moving the gate out. I may be talking rubbish but it won't hurt to check.

At the same point the shutter timing goes out as there is a bit of smearing (look at the white patch on the chart). It pops back at about 2:35 and the sharpness improves. I would be checking for dirt and film residue, especially around the gate.

About the supply/take up spool. I measured the supply and it seemed on spec. The take-up was also on spec pressure-wise but a tad wobbly, like it's going over traffic bumps, when testing. Not entirelty smooth. Could that impact filmtravel? The 2r (double perf) film is pulled down by two arms and 2pin registered.

Next test will be done with shutter angle closed down a bit, from it's native 160 to 155 and 140, and perhaps 135 and 120 too.

[Jefta Varwijk]

Another test, done early january 2025. Tested two newly aquired "balanced" mags at both 120º and 160º shutter. Also tested my older magazine used in earlier tests at those two shutters (showing a problem at 160 that is solved by 120), and also played around a bit with potential lightleaks (not counting the big red lightleak that got onto the whole film) and some tests regarding some separation around the filmgate on the magazineplate. (it does not seem to have any effect at 24fps).

Conclusion: the 2 newly aquired magazines pretty much solve all problems, and the earlier magazine (its an early serial number too) has some problems that might be solved by 120º shutter, but still would need some hispeed testing at 120º.

There is some wobble at 500fps with the 'new' 400ft mag that I don't see at 300fps. Could be a tripod/tripodplate thing. It's easily stabilised and looks great after stabilisation.