IBE Optics HDx35 MK III B4-PL Adapter

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Steve Fishwick

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IBE Optics HDx35 MK III B4-PL Adapter

PostTue Sep 27, 2022 7:24 pm

Has anyone any experience of using this on a PL mount Ursa, with B4 lenses. I know it's expensive and my Ursa Broadcast already has an excellent 4K B4 mount, but I want to buy a PL mount and use proper cine lenses too, whilst using it as an ENG camera also, and ideally I'd like to swap quickly and reliably between the 2 form factors, at a moments notice , without using the torque screwdriver on the mount every time. It would also be useful to have the full sensor quality and flexibility, at all times. I know this won't change DOF with B4s and I don't care about that for ENG work.

What I would like to know is optical quality. From my calculations light loss is more or less equal (2.5 stops loss with this adaptor but full sensor increased sensitivity versus 1.1 stops loss with the BMD mount and only a 4K window). I've found a local place to rent it (there's the Arri one too but that's typically more expensive again), and when I fit the PL mount I will test them but if anyone has direct experience, I'd be very grateful to know what they think.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 7:15 am

Steve Fishwick wrote:Has anyone any experience of using this on a PL mount Ursa, with B4 lenses.


It appears not. But I have been thinking how flexible this could really be. Imagine shooting, say a documentary, in my case, in a very cinematic way with a couple of say Pictor zooms and then being able to go beyond their limitations, at an instant, for some parts of the film by slapping on a B4, with their huge reach from macro to extreme telephoto all on the same full sensor, on the same camera.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 4:02 pm

Well , I recently picked up a MK II. ( very cheap )
Subjectively it appears to suffer less CA and flare than other options I’ve tried. (MTF)
Obviously a lot depends on the lens you use , I have tried with a fujinon 7.8-128mm ( x21 ) HD B4 lens as well as a Fujinon B4 Cinema lens.

As I’ve not had much of an opportunity to do quality testing , I decided not to comment.

i currently have it hooked up to a Big Ursa (PL) with the Fujinon Cinema lens if there are any particular test you woukd like me to try - I can see what I can do.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 5:04 pm

Thanks very much Andy, that's very kind. I notice from Abel Cine (who commissioned these) that the III is designed for sensors up to 30.2 mm, whereas the II (x2, is that yours?) is for sensors up to 23mm. Unfortunately the UBG2 I have is 23.10, so only just being too big for the II, but if I recall the big Ursa you have had a slightly smaller sensor, so that figures. But it may mean a lot of crop for the UBG2, with the III.

I'm not sure of what test you could perform but I would be very interested in your impressions of sharpness. I believe the MFT one required the use of doubler so therefore almost impractical and hard to maintain any good quality. With the HD lenses you have tried, for example, how does it compare in sharpness to those lenses on a 2/3" HD ENG camera?
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 5:33 pm

Well I also have a couple of 2/3” B4 HD cameras.
I’d say they are very similar in overall sharpness - but the Ursa is sharper in the centre.
The studio cameras have lens shading corrections , but the Ursa does not , so there is some falloff at the edges wide open.

I have the HDX35 MKII not the x2. I am not certain what the differences are between the MKII and the MKIII. The MKII is for an S35 sensor with a 30.2mm sensor.
See https://cvp.com/pdf/HDx35_Mark_II_Datasheet.pdf
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 6:09 pm

BTW - as far as the MTF and the requirement for using a doubler - I use the B4-EF from MTF but with an EF x1.4 extender - that helps with the image circle. ( a x2 extender unfortunately causes bad flares and softness ). As has been mentioned many times - the MTF doesn’t account for longitudinal corrections - so the image suffers more CA than the IBE.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostWed Sep 28, 2022 7:47 pm

Thanks Andy. The only thing I could find is, "The HDx35 Mk III features a new contour to fit more cameras than the Mark II adapter." but I don't know what that means, perhaps the rear clearance. The Ursa Broadcast G2 I have has CA comp for certain lenses but not shading. Is that fall off severe and only wide open?
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 9:56 am

Okay - I did a few tests.
The first is with a Canon HD-EC HJ21 lens at 40mm - iris wide open (T2.1) - the waveform shows the minimal rolloff ).
falloff-HDEC-21-Iris-40mm.png
falloff-HDEC-21-Iris-40mm.png (44.65 KiB) Viewed 767 times

The second is of a test chart (I apologise that the ink on my printer isn't very black - and that really is how it looks )

T2.1.jpg
T2.1.jpg (679.01 KiB) Viewed 767 times


And the final is with the canon set to T5.6
T5.6.jpg
T5.6.jpg (697.45 KiB) Viewed 767 times


I think the centre resolution limits are actually with my printer and not the lens.
I may do a few more tests when a professionally printed resolution chart arrives.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 9:57 am

And the final image - the HDX35 with no lens fitted.
There is certainly falloff introduced by the HDX35.
The camera used for the tests was a Panasonic BS1H - and I confirmed that the image circle for the HDX35 is S35 and not a lot more. With the BS1H in full sensor mode ( 35mm ) it's quite clear :D
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rolloff-no-lens.png
rolloff-no-lens.png (10.98 KiB) Viewed 767 times
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 12:23 pm

Thanks so much Andy. I would say that is pretty darn good, I am very impressed. Would you agree? I should do some similar tests with the stock 4K B4 mount on the UBG2, it might take a while for me to get hold of a HJ21, though I'll give it a try - Am I correct in what I am seeing the HJ21 looks to have more contrast, therefore appears sharper?

Just so anyone following this thread knows, Andy PMed me very quickly and offered to do these tests with his adaptor, for which I am very grateful.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 12:46 pm

Given the lens is originally intended for B4 - I am also impressed.
There are some definite fringes - and there is rolloff from both the lens and adapter - and there is a loss of definition to the corners. It certainly appears to resolve better than HD. My tests weren’t the best ( don’t really have the time or equipment to do better tests ). Definite distortion from the B4 at 40mm - might do some tests to see if there is a point in the zoom range that barrel / pincushion is minimal.
All in all given the parfocal features and wide zoom ranges its a good compromise.

I do actually also have a Ursa mini Pro 4.6k and I have the B4 adapter - but I totally agree its not practical to change the mount during shoots.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 1:37 pm

Andy Coulthurst wrote:Given the lens is originally intended for B4 - I am also impressed.
There are some definite fringes - and there is rolloff from both the lens and adapter - and there is a loss of definition to the corners. It certainly appears to resolve better than HD.


Yes Canon and Fujinon continue the tradition of their old marketing tricks - SD, HD, 4K and 8K nominal lenses. A lens is not like an OLPF, cutting off at some arbitrary resolution. Canon used to wheel out the great Larry Thorpe to justify scientifically you spending 3 x on a HD or 4K lens, without so much as an MTF chart in sight to prove it - I hope he's well and still going strong. For the 4K UHDxs CJ12e 4.3B, for example Canon state "Thanks to the precision of its high-grade components and assembly, the lens achieves high 4K lens camera performance even when the built-in 2x extender has been engaged." - how is that even possible? Is it then an 8K lens, really?

8K Eng lenses required the need to go to a 1.25" mount, not because of the limiting capabilities of resolution from 2/3" lenses but because the the 9x6mm sensor would necessitate a pixel size of around 1.1microns, which is impractical on all fronts, professionally.

I should start by testing the J16 I have at hand, since that seems to clearly exceed SD rez and even HD to my unscientific eyes. Then I'll try and rent a HJ21 and one of these adaptors.
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Howard Roll

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 2:30 pm

Looks pretty good. The effective aperture wide open is about t5 so that’s definitely helping the resolution. On the t5.6 grab where the effective aperture is close to t14 you can see dust on the sensor which would normally be invisible at t5.6.

Good Luck
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 2:43 pm

Howard Roll wrote:Looks pretty good. The effective aperture wide open is about t5 so that’s definitely helping the resolution. On the t5.6 grab where the effective aperture is close to t14 you can see dust on the sensor which would normally be invisible at t5.6.


Yes I think the HJ21 at T2.1 looks better. These adaptors are a 2.5 stop light loss Howard, so that would be between T11 and T14 no? Normally at such a small aperture diffraction would substantially reduce resolution but that doesn't seem to be the case here.
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Howard Roll

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 4:03 pm

Two stops above T5.6 would be T11, another half stop puts it somewhere between T13 and T14.

The diffraction limit of the BS1H at 1:1 4K sets in at about T11. The chart only appears to be about 1.4K so the trumpets aren't super helpful. This is probably hovering right at the edge of the limit, at T2.1 the center is sharper, at T5.6 the corners are sharper.

Good Luck
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 5:01 pm

Howard Roll wrote:The chart only appears to be about 1.4K so the trumpets aren't super helpful.


It's a self printed ISO-12233 chart which should show a range from 100 - 4000 Line Width / Pixel Height and hyperbolic wedges. The Jpeg images are DCI 4K so I think it's showing rather more than 1.4K. There's some slight CA on both lenses, which is pretty identical, so I assume that is down to the adaptor.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 5:34 pm

Yes DCI 4K , and I would have loved to upload a uncompressed frame, but the forum has upload limits.
Video was recorded in camera , prores , played in vlc , and a single frame captured. Sadly the BS1H only has max 3G SDI output , and my hdmi monitor is only HD - so I may not have completely nailed focus. I performed focus by maximising the amplitude of the central gratings using a waveform monitor.
And as I say , when a better chart arrives - I may revisit.
And 1400 lines over 1080 pixels would put this as better than HD , but well under 4K.
The HP inkjet used to print the chart has a maximum resolution of 2400 x 1200 dpi.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 6:38 pm

You can actually see the fibre structure of the printing paper, which appears finer than the chart resolution, Andy. It also may depends on how well the Panasonic camera down samples from 6K to 4K in camera. Despite too what I said earlier there will be a natural limit for the HD lens and a 4K lens would make an interesting comparison. Anyway that's beyond the call of duty for what you've done already Andy, thanks once again.

I'll try and get hold of some lenses and when I buy the PL mount, there's a localish place renting out this adaptor too, so hopefully I can contribute some useful mount comparisons. I'm very impressed and encouraged nonetheless, it's only that slight CA that suggests the 3 chip correction is not perfect, which is probably true of the BMD B4 mount, under such conditions too, since it's a big ask of any optical adaptor, like these, for a single sensor.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 7:08 pm

The Panasonic is not downsampling , DCI 4K is a crop. 6K mode is 35.6mm x 23.9mm , 4K is S35 24mm x 16 mm.
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Howard Roll

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 02, 2022 10:46 pm

You can always zoom out .5x to increase the effectiveness of the chart and mitigate the effects of printer resolution at the center. Obviously this won’t reveal anything about corner resolution unless you print 4 charts. Thanks for posting.

Good Luck

P.S. Your sensor has dandruff, on a 4K monitor I can see the dust on the T2.1 grab as well.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostMon Oct 03, 2022 5:57 am

Andy Coulthurst wrote:The Panasonic is not downsampling , DCI 4K is a crop. 6K mode is 35.6mm x 23.9mm , 4K is S35 24mm x 16 mm.


Yes of course, I realise now that camera is FF 6k. Then any lens or adaptor that can exceed, or approach 3.2K of useful resolution, can be considered '4K' on a single bayer sensor of 4K photosites. I would just add, yet again Andy :) , that if you have a good quality PL mount prime, it would be very easy to see adaptor + B4 lens resolution loss, if any, by photographing the same chart twice, with both, if you have time. Then when I test the UBG2 with the same chart, with the same lens hopefully, we can compare all 3. Thanks again.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 09, 2022 12:03 pm

Okay - so here's a view of a better chart ( but not as good lighting ).
Apologies - but the chart is 78cm wide - and finding space to shoot it in my house was difficult.
Same lens - Canon HJ21 - again T2.1
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 09, 2022 1:44 pm

Howard Roll wrote:You can always zoom out .5x to increase the effectiveness of the chart and mitigate the effects of printer resolution at the center. Obviously this won’t reveal anything about corner resolution unless you print 4 charts. Thanks for posting.

Good Luck

P.S. Your sensor has dandruff, on a 4K monitor I can see the dust on the T2.1 grab as well.

I got rid of the single spec of dust. :-)
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 09, 2022 2:20 pm

Thanks Andy, that does show quite pronounced edge fall-off, at the corners, though there is no apparent CA, this time, which is curious. At the centre the performance of the lens is rather good.

I have tried to print off this chart to begin tests, with what I've got, on the UBG2, unfortunately my printer is just not up to the job. I'm going to try a commercial printer - it will be cheaper than buying the chart, anyway.
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Andy Coulthurst

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 09, 2022 2:37 pm

There is definitely CA , the lighting wasn’t as bright - so it isn’t as apparent.
It’s also likely I was off-centre - so the rolloff might be worse on one side.
It’s clear the chart I printed was the limit in the original captures. I’ll do some further tests next weekend if I get the chance.
And yes - domestic printers aren’t really upto the job at A4 size.
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Steve Fishwick

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Re: IBE Optics HDx35 MK III B4-PL Adapter

PostSun Oct 09, 2022 3:07 pm

Andy Coulthurst wrote:There is definitely CA , the lighting wasn’t as bright - so it isn’t as apparent.


Yes, I now see it but only at the edge of frames, whereas it was clearly in the centre too before. There seems to be difference in horizontal and vertical resolution at the edges, which is a centering issue, with these charts, but as you say, you were off-centre. It's not nearly as bad as I suggested and is certainly better, as would be expected, than a SD J16, I just tested, in this respect. I won't publish the images because the chart is wrong and not properly squared but it's enough to realise I need to buy that Fuji LA16 4K sooner rather than later, although subjectively it takes very nice images and is very sharp at the centre. I think your IBE adaptor is holding up quite well.

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