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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 :)

4 New OLPF's for Dragon!

John Marchant said:
IR landscapes... - I personally like the Tokina 11-16 for making big skies and for practicality. Although its not very sharp, it does behave in IR and takes a 77mm filter OK. The Nikon 14-24 is ultrasharp and fantastic for wide landscape imagery, but a slightly bigger chunk of glass, and won't take screw-on filters which is a little annoying in this context.

All the Nikon glass is good in IR, but older stuff needs stopping down from wide open for sharpness, and still suffers with coma etc.

I like the Canon 70-200 too, although again the Nikon 70-200 is better in IR.

Most older cine lenses work pretty well, but can be more prone to hotspots reflecting the shape of the aperture. The stuff that ironically is not always great is modern cine glass, especially zooms, with complex and effective coatings.
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good answer, thanks John.

I'll run around a bit with the Tokina and the Canon 70-200 - it's always nice to experiment with glass that is already familiar, and my existing IR filter is a 77mm screw-in, which ought to fit both lenses. Both great lenses. This should give me hours of fun.
 
Don't most canon lenses go beyond infinity to deal with backfocus drift on consumer cameras? Also you could always tweak the back focus position to "make it work" without any glass no? (Not a good fix for a production camera that needs to remain calibrated, but maybe good for a hobbyist who wants to do some personal projects).
 
They do indeed, but from experience most canon lenses for example, even with beyond infinity focus and with the backfocus screw wound to its end stop, still don't hit infinity without th OLPF in place. Sometimes with zooms they do at some focal lengths and not others as they go very much away from being parfocal at all in this configuration.
 
FYI - focus shift due to a flat plane glass element is given as:

Δz = t (n-1)/n where t is plane thickness and n is refractive index.

The OLPF is nearly 3mm thick on dragon, hence its removal usually puts the focal plane forward beyond the adjustment range :)
 
John Marchant said:
Coming shortly we have our take on a Low-con option in LLO and STH variations. These are under testing and revision right now, but we wanted to let everyone that they're much more than a concept at this point, as a low-con OLPF is a much sought after piece of the Dragon puzzle.
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Is there a way to preorder?

Thanks

Pat
 
Hey John, killer idea. Can't wait to start swapping the olpf on my camera.
A quick question for you regarding back focus...when swapping in one of your olpf filter packs, are we going to need to adjust back focus or do they match red's thickness and don't need any adjustment?
Also, my wife is traveling to the UK for business, any chance she can pick up a couple of filters and save on the VAT?
Thanks.
Jay
 
Hi Jay,

If the timing works, its fine to pick up here - however only if I'm shipping out of country do we not charge tax; the items are of course my gift to you for import purposes ;) So it should work just fine.

Backfocus should be fine, but I recommend double checking if you're relying on focus marks. The filters match RED's original thickness, but even so they're made from different materials. No general issue though - we made sure to match as best we can.
 
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One last question John, with your olpf filters, what olpf setting do you use in the camera? More importantly for the IR full spectrum ones...
Love the IR stills...I'm trying to get Adorama to buy a Dragon Monochrome...I keep telling them I'll rent it all the time...Those are kinda tough to find.
I'll probably just have them shipped over here to NYC.
Thanks.
 
For the IR filters, the LLO calibration works well, although its up to you in fact... For the upcoming low-con filters, they're intended to match the LLO and STH calibration as far as possible.
 
A small update: A nice big box of these was built, tested and packaged today for shipping. Anyone who ordered just a plain vanilla Full Spectrum filter and no extras will ship tomorrow (slightly ahead of my original plan). Some other small acc's are arriving this week and we'll fill out the orders as those come in.

I've offered free shipping on all our stuff on the basis of grouping the items. If you have an order with accessories too and can't wait to get your hands on your filter, just email or PM me and I can arrange to split your delivery for a small cost, or expedite it with UPS or similar if you like.
 
Do you have back focus problems if you use apochromatic lenses like some Leica r's?

I think in theory they are corrected for IR so someone can use all these without olpf and be fine? (other than the dust problems that can be corrected with a clear olpf).

Also if I use the fixed IR olpf that will mean that I'll have a limited creativity as only a specific wavelength of the IR will be able to enter in. If you use a clear olpf only to maintain focus then someone who wants to be creative can have 5-6 choices at least of different IR frequencies to play with putting the appropriate IR wavelength filters in front.

Also someone can use different IR artificial light frequencies (BH sells those lights) of different wavelengths.
So I think a clear olpf that is just for back focus reasons may be more beneficial for IR? I might be wrong. Just asking.

By the way John, do US orders have to pay vat?
 
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Hey John, Just to be clear and because it's what I really want, and please excuse my ignorance, is there or will you be making an OLPF that is for monochrome shooting to the best extent possible minus buying a monochrome dragon for regular dragon? thx. I need 2.
 
John, Are your OLPFs of the same thickness as the RED filters? I've asked a similar question before concerning the RED OLPFs and got no answer. Are the different RED OLPFs all the same thickness? When RED converts a camera to the interchangeable OLPF system, does anything change in the numbers of pieces of glass in front of the sensor or the thickness of the the glass? I ask because we have noticed focus issues after camera have been converted. Even though the depth is set exactly as it was prior to the conversion. We set the depth using a DENIZ multi FDC. This would suggest that something changes as part of the conversion at RED. Either additional glass, or a change to the thickness of the glass. I was hoping perhaps you might have some thoughts on the matter.
 
Rob Skates, I cannot answer for John on his thickness, but I am certainly thinking that the holder constrains the variance. As to genuine RED OLPFs (ie, the actual glass), they are all the same thickness to help ensure backfocus does not change between OLPF swaps*. However, after conversation from "fixed" OLPF to "swappable", a backfocus check is recommended. There could be slight variance in where the backfocus hits post-conversion.

* FWIW, checking backfocus when swapping between the swappable OLPFs is recommended as the depth can be affected by how much torque is applied during the install of the OLPF tray each time. Again, variance should be only slight and not even statistically significant if swaps are done the same each time - if at all, but a good best practice.
 
Hi, to answer a couple of posts:

Yes, our OLPFs are of matching thickness. There should be no significant backfocus change, however we're talking tiny tiny tolerances here - its always recommended (and dead easy) to check after a change. If you've seen significant change post-service for the swappable system its probably just that the position of the sensor has been adjusted or set to a nominal value. The number and thickness of pieces of glass is identical, but again, even incredibly tiny movements and alignment differences can affect focus.

For monochrome shooting on colour dragon, our Full Spectrum filter, with an off-the shelf UV/IR on the front of the lens, plus appropriate colour filter as needed is as close as you'll get sharpness-wise. You may get spatial aliasing, but it hides better in mono... and FWIW, I can provoke it with a chart, but seldom in the real world.

@Lakis - you want the full spectrum OLPF too. It'll give you everything, and allow you to choose your filtration to pick the colour (or IR) range you want. Bear in mind however that our IR spectrum filter is a long-pass... ie. all kinds of near-IR will work, up to the point where the sensor stops responding.

On tax/VAT - US and other export orders do not pay VAT. EU orders with a VAT number do not pay VAT. UK orders do, but can claim it back if VAT registered.
 
geoffboyle said:
This is absolutely brilliant John.
I look forward to trying the LC skin, it sounds like its been made for me :-)

Oh and I think you're not charging enough for them!
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Thanks Geoff. There's certainly not that much margin in these, but I want to get them out there. I believe in passing on a good deal if you can find one.

What's good for the camera's flexibility and reputation is good for my rental business too. And beyond all that, I want these toys to shoot with myself!
 
Thanks Brent, We have found that we now have to set the flange to focal depth of the swappable OLPF converted cameras to 52mm +3 in order for lenses to come up or focus properly. Not just one lens but every lens, Zeiss, Cooke, Angenieux. Prior to the conversion we set the depth to 52mm and lenses came up just fine. This happened with two cameras. both were fine with a 52mm depth prior to conversion. Both now have to be set to 52mm +3 post conversion. We check the operational condition of cameras and lenses both visually with monitors and with tools Deniz depth checker, lens projectors, optical bench, etc. One of the reasons for this level of scrutiny is certainty. If the flange to focal distance is set properly and a lens other than ours comes up soft we can say with certainty that it is the lens not our cameras. Sorry for the long explanation, but we are trying to determine what caused the change and will all post conversion cameras now have to be set to a depth of 52mm +3. The only explanation we could come up with is the addition of glass in the optical path or a change in the thickness of the glass in the optical path. If the OLPFs are the same in the pre and post converted cameras then that rules out the OLPF. Was the glass in front of the sensor added post conversion? If it was, then the addition of the glass is likely the cause of the change in the apparent depth. If there was always glass in front of the sensor was it changed to a different piece of glass as part of the swappable conversion? If so is it of a different thickness?
 
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