For Plane Junkies

[Bob Hart]

It may well be posted here somewhere else but if not, here is a link to Philip Bloom's latest with the EX1/Ultimate.

http://exposureroom.com/members/phil...9bd83de92730f/

[Phil Bloom]

ha! was just about to send you the link Bob.

First time shooting on production Ultimate, mounted upside down and with Redrock Mattebox

[Bob Hart]

Phil.

In regard the 12mm-24mm, if it is like the Nikon one, it will be f4 constant. As you discovered, a wild lens and when backfocus is right, quite sharp for a zoom but softer than a prime.

It is extremely handy in a confined space. You may get some weird perspectives and if shooting in a room, you might choose to stay level with centre of windows and shoot straight ahead, not tilted or you get these way-out trapezoid shapes.

These do not always intercut well with other takes with longer lenses but a local director here has used it on a feature for a fight scene. He shot with it at floor level and moved it about on a Skater Dolly. For a dynamic follow down an alleyway or through the weeds, it is excellent.

Depending on how wide your view is on the Ultimate, you may get a vignette at 12mm. It should be gone by about 16mm.

Groundglass artifacts are sometimes provoked in high contrast outdoors conditions with the Extreme and Mini35, high bright overcast and uniform bright featureless backdrops, the main culprits.

My Agus35 (disk) was okay except for my fingerprint on the disk which came up as a flicker.

The Ultimate should be fine. You will likely need to prop the iris lever wide-open at f4 which leaves it a little soft but the Ultimate may well tolerate coming back to f8 which will sharpen things up a little.

[Chris Barcellos]

Says private at the link.....do I have to be invited ?

[Bob Hart]

Given that it is an extract from a copyright work and motion images can be downloaded, there may have been a decision to restrict it after I accessed it which was five hours after the clip was made live.

There were quite a few responsive comments posted under it. Philip will no doubt advise soon enough.

The clip steered away from just being clips of warbirds and focused also on the human element with some beautiful focus pulls along lines of onlookers, and people with the warbirds passing soft in background. Think "Empire of the Sun" and the Mustang passing in background and you get the general picture.

There were a couple of long shots of aircraft taxying in a line head-on to the camera, crossing back and forth, also one of my own favourite setups, timelapses and a slow-mo against the clowded sky which is the most hostile circumstance for any groundglass adaptor. I get away with these up to a point with my own home-made spinner arrangement but the Extreme and the Mini35 both artifact in this environment with a long lens especially. The Ultimate is a disk system which is why it works for this particular shot.

All in all, the clip was well and truly up to the standards we have come to routinely expect of Philip's work.

[Paul Frederick]

You can see it here:

http://www.vimeo.com/1343943

...not sure why the exposure room one is private? They are the same. I saw the exposure room one moments after it was posted and before it became private.

This video is indeed exceptional, so check it out!

I wish I could afford an Ultimate, I'd sooooo get one!

[Dennis Murphy]

Originally Posted by Paul Frederick

You can see it here:
http://www.vimeo.com/1343943

Bzzzzzzzzz, needs a password dammit grrrr.

[Andy Wilkinson]

I saw Phil's (et al) Duxford Flying Legends DVD teaser on ER the other night and loved it - not least because, as usual, I was there with a few mates (and we took MANY more than a few bottles of beer and wine with us!). Saw it on Vimeo a day or so ago as well but this one now also requires a password too (found that out as I was about to send the link to my dad tonight). Edit: as I see others have found this out too! Second Edit Fri AM, I see it's now available again on Vimeo.

It was a great event, dramatic skies, ever changing sunshine/light/weather with the wet airframes gleaming in the sunshine as they stormed past (then the odd shower - well this is England) and superb flying in exquisite machines (as always). And then there was the noise! This was one aspect not covered in Phil's teaser. Don't get me wrong the music choice was great, but it's just that there was a different kind of music last Saturday at Duxford!

In fact, one of the Spitfires flew over my house on it's way home this afternoon. Needless to say I rushed out into the garden as soon as I heard it! He did a nice barrel roll for me too (before I had time to get my camera out of course!)

[Drew Cusick]

The planes flying up the screen at ~ 40 sec look all flickery. Is that the EX1 coming into play?

[Andrew Kufahl]

Found it here for those still looking for it:

http://www.vimeo.com/channel7178

[Bob Hart]

Drew.


It looks to me more like a combination of 25P, fast shutter and coding for web issue.

The beauty of a disk based system is that you can run a fast shutter speed and not pick up the groundglass texture.

The same motion signature seems to be there on the other shots, just that this one combines high contrast and fast moving objects which makes it all the more apparent. Motion picture film presented on the web would have a similar look, possibly a little less apparent because of motion blur from a slower shutter.

If you have a closer look, you may see a sort of double-image flick-back going on. You sometimes see this when software converts progressive to interlace or frame blending is not selected off.

Philip may have shot this at 50P for slow-mo but reproduced it in realtime which can also create this apperarance.

If you look closely at the motion signature of this unrelated clip

http://exposureroom.com/members/DARA...0680b99a8cccc/

in the first portion, which is 50P to 25P reproducing real-time you will observe a sort of flicker which is not apparent in the slow-mo render of the same footage which follows. I am however only guessing.

Rolling shutter seems to be more of a distortion thing.

[Drew Cusick]

Thanks for the explanation.

[Chris Barcellos]

Originally Posted by Bob Hart

Drew.


The beauty of a disk based system is that you can run a fast shutter speed and not pick up the groundglass texture.

I am working on a second generation self built disk since everyone in the vibrating market seems to be rolling that way. So, Bob, if you are shooting fast enough shutter speed don't you risk catching some kind of disk "signature" too. Don't you have the potential of freezing the disk or some of its imperfections....

[Bob Hart]

Chris.


EDITED POST - SOME MORE INFO ADDED.

I am a little careless with the wordstuff sometimes. I should have have said "faster" not "fast".

I am using a full CD-R sized optical glass disk and only about 24mm inwards from the outer diameter to my lower frame edge (upper as viewed). The rest of the disk is wasted space. 1500rpm is approximately the rpm with a new battery. That seems good for 1/250th sec in good light f1.8 lenses wide-open.

As silly as it may seem, I have not tried higher shutter speeds than 1/250th sec on my disk adaptor. Now that you have set me off, I'll give it a try.

I did try 1/400th sec with a modified Letus XL with a 1.5mm to 2mm excursion. It was not as grainy but had a visible pattern, just tolerable except for the usual culprits of grey skies and uniformly light coloured plain objects. That's on YouTube as "Letus for XL modified" in my clips under DARANGULAFILM here :-

http://www.youtube.com/watch?v=-O-Dl7oZTZs

It is the inner areas of a disk that start to become visible first. I have some variations in the groundglass texture towards the outer edge which become visible as a travelling artifact moving across the frame.

I could run the disk faster for a higher shutter speed but the wide diameter disk is only 0.9mm thick once I have dressed it down which is a bit thin for the certifugal forces acting on it and the gyroscopic resistance to pans and tilts.

I've broken one and it flew off into the front prism. It was not a good look unless you like rainbows.

If I was going with a wide diameter disk to chase the higher shutter speeds, my inclination if I was an engineer would be to slave an electric motor in the manner of a video drum motor to the frame rate of the camera and make a strong large metal or plastic disk with several small portholes with smaller groundglasses in it so I could forget about the gyro problem.

With a phase adjustment to reposition the portholes. one would then be able to select different grades of diffusers on the fly if they were fitted. There would be a visible transition however it would be fairly quick.

It is outside of my abilities but there lies the next challenge for the Le brothers, P+S Technik Cinevate or SGPro or Redreock for that matter. They are already halfway there with their controllable motors.

The only downside would be that the system would likely not cope with violent dutches or rolling movements of the camera.

Big disks also take up a lot of space.

If you are dressing your own glass disks, my method was to glue them onto a machined heavy brass platen about 2mm wider than the disk with paraffin wax. I have a larger glass disk sitting on the bottom of a thing which looks like a small cement mixer made from 160mm sewer pipe and caps. I used a Ford Falcon water pump as the spindle with a thick spacer, then the mixer barrel going where the fan pulley fits. 60rpm is about right.

The platen needs to be about 18mm to 20mm thick to get enough weight bearing on the glass, otherwise it sticks and loops around instead of rolling.

The slurry in the barrel need not cover the entire platen when the barrel is at about a cement mixer tilt. I generally use about a half-dessert spoon of AO6 in about a small coffeecup full of water.

If you decide to backpolish with cerium oxide, I find that a glass grinding disk with hard felt glued on with yellow toluene based contact glue works as a polishing surface.

Dress the cerium oxide into the felt pad with the back face of the platen for a few minutes. Then I turn the platen over and backpolish for about 15 seconds max. A minute can make the disk too transparent.

This is a bit of a dark art and highly unpredictable. I got close, but never did achieve the quality of the the original disk I backpolished. A tiny trace of aerial image passthrough seems to add clarity. There is a tendency for the ghosting effect.

The platen is placed on a stove top, some wax shaved onto it with a grater, the disk laid on the dry wax, then the heat turned for only as long as it takes to melt and travel the wax beneath the glass, then I slide the platen off onto a cooler part of the stove to cool and set.

To get the disk off again, I boil the platen and disk in a pot of water with a bit of dishwash detergent added. Slide the disk off sideways with a metal meat skewer or two if it doesn't come off on its own. Leave it in the water to cool down as thermal shock will crack it if you bring it out hot into the air with evaporating water on it.

The larger glass disk in the bottom of the barrel which is the dressing surface needs to sit on a piece of inner tube or rubber foam, otherwise it slides around and you don't get a good grind. When the disk is ground, you boil it off the platen in a pot of water. Let the water cool down before you extract the disk otherwise thermal shock will crack the disk if you expose it hot to cool air.

It is helpful but not essential to machine a groove in the tyre area of the rim of the platen close to the face the disk is glued onto and fit a thin "O" ring in the groove for a tyre. This aids the platen a little in rolling and not skidding and helps protect the inner wall of the barrel from wear. This "tyre" needs to be close to the front otherwise there is sometimes a tendency for the platen to chatter and cause variations in the texture of the grind along radius lines.

[Bob Hart]

Chris.


I took the thing out into the bright sunlight with some 12-30pm bright clouds and Sigma 28mm f1.8 lens iris at f5.6. No camcorder ND was selected. Camcorder iris was side open. O db gain was selected. Using a camera this way is likely to cause problems with the image through flare across the surface of the CCDs. I shot against the light to provoke anything that is there.

It seems that a CD-R sized optical glass disk is good for a shutter of 1/2500 sec on a Sony FX1 at about 1500rpm on the disk.

However that is viewing via the LCD screen which is not a good judgement. I'll capture and post it on exposureroom sometime soon. You would probably run out of light before you freeze the disk texture on a disk of about 125mm diameter.