The GetDPI Photography Forum

Great to see you here. Join our insightful photographic forum today and start tapping into a huge wealth of photographic knowledge. Completing our simple registration process will allow you to gain access to exclusive content, add your own topics and posts, share your work and connect with other members through your own private inbox! And don’t forget to say hi!

New Cambo Actus for Digital Backs

Steve Hendrix

Well-known member
Thanks Steve. I don't doubt you do your very best in supporting your customers to make good choices.

My observations has been though that the information how sensor+lens play together and what-is-what (difference between recoverable casts and irrecoverable casts) is not very wide-spread, not among photographers and even not among designers. I hold up SK28 as one evidence of that -- the optical designers at Schneider cannot have tested that on 6um Dalsa although the leading products on the market were already using it, and I think the Cambo Actus is another evidence of the same, I find it unlikely that Cambo would have designed this camera in this way if they were aware of the wide angle limitations. This disconnect between sensor, lens and camera body designsers is a mystery to me.

It's easy for me to say as a layman on the side, but I do it anyway; I think that if I had been a dealer I would not market the Cambo Actus, because it can't hold what the design promises. For the same reason some dealers have pulled the SK28 from the shelf. Sure you can use it with longer lenses and not shift the wides and/or shoot B&W but it's a strange package. But as long as you inform your customers with the limitations so they can make an educated decision it's of course okay.

My skepiticism towards this camera is however based on this. Anyway, I think the best thing that could happen in tech cam land is that a tech-wide friendly CMOS digital back appears, which would make the Cambo Actus to a great concept combined with lightweight (and in comparison affordable) Schneider wides you get a small light view camera with flexible movements and very easy to use thanks to live view. Until then, I think it's a severely crippled concept.

Anders - we hope for the same things! Closer collaboration between the various manufacturing elements would be helpful - perhaps the P1/Alpa relationship contributes to that.

Regarding the Actus - this is a good example of how a subjective viewpoint can produce a limited perspective. Just this morning, I had a call from a good client (Nye) who asked about the Actus. As we discussed it, we touched on the restrictions that the sensor would place on the lenses (I said that just for you, Anders, so you'd know I attached the appropriate responsibility!) :)

I told him this product - at least at this time - is not an ideal scenic shooting solution for use with his Sony A7R. As we discussed where the lines were drawn on the use, he specified that he doesn't shoot wide landscapes anyway, he shoots with medium and longer lenses. So - his interest remains. It's a good lesson that products don't always fit into the expected box. And actually, his desired use of the camera could be exactly what Cambo had in mind when producing it - realizing the limitations, perhaps. And if sensor design takes a positive step forward with regard to the issue of crosstalk, Cambo has already a good design in place to take advantage of that.


Steve Hendrix
Capture Integration
 
Last edited:

Georg Baumann

Subscriber Member
Would it be a reasonable request to ask for a recommendation list of focal lengths for the actus, perhaps explaining with a few words the ins and outs of wider lenses as well?

You guys need to consider that there are people around who are new to the tech camera world but potential prospects.

I would have fallen straight into a trap with the actus and wide angles if it were not for this discussion here.

Thanks for that.
 

torger

Active member
I'd like to see such a list as well. Although I personally know the digital tech lens lines quite well, I don't know much of what's available in the Mamiya RZ and other adaptable lens lines.

From analysis I've done on raw files I've got the general recommendation I would give for a Sony CMOS MF sensor (CFV-50c, H5D-50c, Credo 50, IQ150, IQ250) is to not exceed about 30 degrees (60 degree cone) to avoid getting too much of the irrecoverable crosstalk. For horizontal orientation you may be able to stretch it a few more degrees. This does not mean than below 30 degrees there is zero crosstalk, just that there is an "acceptable level" of crosstalk below this angle, ie generally not possible to see any artifacts even if you search for them. Naturally this is based on my judgement, a different person could judge otherwise.

For symmetric lenses you should be able to approximate with simple trigonometry, <image circle diameter> = 2 x <focal length> x tan(<acceptable crosstalk angle>).

A few examples, SK28 = 32mm image circle (smaller than the sensor), SK35 = 2 x 35 x tan(30) = 40mm, SK43 = 2 x 43 x tan(30) = 50mm, SK60 70mm, SK72 85mm.

That is you need to get up to almost 80mm focal length before you have a full 90mm image circle with stable performance, in practice it's a bit less though as you won't shift to hard vignetting and the sensor corners can reach a bit farther than 30 degrees thanks to offset microlenses. The SK72 should be 100% usable, while you really can't use the full 110mm image circle of the SK60, but you might not like the sharpness falloff out there anyway. Depending on your taste and the scene you're shooting you can also stretch it further into the crosstalk zone, the image circle examples above is probably more conservative than many dealers would recommend from their testing. Of course, it's also a matter of taste how much image circle you need to be satisfied with the available movement range.

The 44x33mm sensor has 55mm diagonal, for center shots you can undercut a bit thanks to offset microlenses and better crosstalk suppression in short side direction, the 43mm work just fine in center (despite the 50mm image circle in the calculation above) and maybe even the 35mm but I doubt that (I have no test shots for that lens so I cannot sanity check that).

Note that there's no gradual degradation like vignetting, when you shift beyond a certain limit you can get a quite sudden breakdown, more so than on the CCD sensors. I think this is due to the offset microlenses (actually offset photodiodes), but I'm not sure.

Not all lenses are symmetric though. When it comes to retrofocus lenses it may not be so easy to figure out at what angle they deliver the the light, it's unfortunate that it's not available in the data sheets. If you have the lens you can measure it using a laser pointer, a piece of paper and careful perpendicular setup. I don't really know what the data on the Rodenstock Digarons are, but I do know that the Rodenstock 32mm is more retrofocus design than the Rodenstock 40mm, so it may not be as simple that the longer focal length increases usable image circle.

A good test to see if you get irrecoverable casts is to shoot two LCC shots, one with red filter and one normal neutral white. Apply the white LCC on the red, if it's not flat red with even saturation and color then you're having irrecoverable color cast (ie crosstalk). The advantage with this type of test rather than a real shot is that it's less risk that you happen to shoot a scene where crosstalk doesn't notice much and then over-estimate the image circle and get disappointment later on when you shoot another scene. A real scene shot is good to see how far you may be able to stretch it without noticing too much, while the artificial shots are good to document the actual performance so you know in which range you can trust the system regardless of the scene contents.
 
Last edited:

dougpeterson

Workshop Member
Would it be a reasonable request to ask for a recommendation list of focal lengths for the actus, perhaps explaining with a few words the ins and outs of wider lenses as well?

You guys need to consider that there are people around who are new to the tech camera world but potential prospects.

I would have fallen straight into a trap with the actus and wide angles if it were not for this discussion here.

Thanks for that.
Assuming you had purchased from a good and experienced dealer you would not have.

It's very much to our benefit, and within our capability, to make sure the full solution is the best one for you.

A comprehensive list of every possible sensor, lens, movement, and focus distance is simply not practical. Even a 28XL and IQ250 (which normally would be a complete non starter for several reasons) would work beautifully on this system - IF you were using it for macro table-top special effects (this is an extremely obscure use-case only being used to illustrate the broader point that there are several variables). But we (DT), and other tech-camera oriented dealers like CI, work every week with clients to test specific combinations, provide rentals which count toward purchase, provide studio space and equipment for those who want to do their own testing but can't arrange insurance for a rental, and have extensive overall experience to help provide very good guidance if none of the above is practical (e.g. the combination is not possible to get without purchase because it is too obscure or one-off).

One published test set you can parse yourself is here. That is specific to a handful of lenses we could gather the same day we had an early IQ250, and is relevant largely to infinity focus distances. We have done other testing in-house and had clients share results from many other kinds of combinations.
 

dougpeterson

Workshop Member
Its not an easy situation. One is reminded of Doug Peterson's chart of cameras and lens compatibilities, and how much criticism he got for combinations that were not included. It gives one pause - there are more variables than players working to resolve them.

The focus on crosstalk is (IMHO) quite welcome, and it may be that Anders has tumbled onto a something overlooked or not well described.
We had referenced (both online and in consultation sessions) the issue of loss of color fidelity in areas of strong color cast many years before Torger started using the technical term Cross Talk (e.g. see for instance this post from when I worked at CI in 2011). I considered such a technical conversation way too technical for practical discussions; I had used instead terms like "color cast which is not fully recoverable". Somehow by giving it a name (despite the name being very technical sounding) more people understood the underlying issue, which is what matters. In some ways it served as branding for the issue to raise awareness of it so instead of saying "color cast which is not fully recoverable leading to a loss of color fidelity" you can just say "cross talk". For that we must all give Torger credit.

Still, I prefer, wherever possible to avoid overly complicated/technical conversations and focus on practical testing and metrics (e.g. up to 10mm of movement with X back and Y lens, or "significantly less movement than X+Y combination) and on providing the opportunity for personal evaluation.
 

Paul2660

Well-known member
From my point of view, yes the issue had been discussed previously but from some reason from those past discussions I always came away thinking it was the lens and or image circle causing the issue. Instead as I have learned from reading and my own testing, it's more due to the sensor involved and the degree of micro lenses on the sensor that cause the light splitting when the light hits the sensor at an angle due to movements. As shown the 50MP kodak in the Hasselblad and 39MP Kodak in the P45+ show very little if any problem with this but do show light falloff as expected.

The 60 and 80MP Dalsa chips have a bigger issue but with most lenses it seems recoverable. There are known exceptions to this with the 80MP Dalsa. Considering everything the Dalsa chips do a very good job but just can't be called on for much of a push from base ISO.

The 50 MP Sony gives a wonderful push in ISO but is much more effected by the color fall off with wides with even small movements. Which is unfortunate as due the 1:3 crop in many shooting situations pushes the photographer to a wider lens. It would for me.

Paul
 

etrump

Well-known member
This thread has taken an interesting turn, it almost seems like the dealers and mfg are getting blamed for not informing buyers about the crosstalk phenomenon which could not be further from the truth. I recall a P1 tech note on this issue dating back to before the P65+.

I personally was informed about it by Steve at C1 before I upgraded to the P65+ and Dave G made a personal call telling me the issue would be exaggerated if I purchased the 180.

Hardly seemed swept under the rug to me. The benefits of the tech cams outweighed the headaches dealing with it.

Now that is my experience, others may vary but the issue and reasons for it has been publicly discussed for sure.
 

alajuela

Active member
This thread has taken an interesting turn, it almost seems like the dealers and mfg are getting blamed for not informing buyers about the crosstalk phenomenon which could not be further from the truth. I recall a P1 tech note on this issue dating back to before the P65+.

I personally was informed about it by Steve at C1 before I upgraded to the P65+ and Dave G made a personal call telling me the issue would be exaggerated if I purchased the 180.

Hardly seemed swept under the rug to me. The benefits of the tech cams outweighed the headaches dealing with it.

Now that is my experience, others may vary but the issue and reasons for it has been publicly discussed for sure.
+1111

I also have chime in here. When I went into the tech camera CI - Chris and Dave were very clear - that since I had a 180 back, the size and angles of the pixels on sensor, I would need Rodenstock Lenses as they were retrofocus, although heavier and more expensive to buy and to add Tilt shift (Cambo) was also an added expense.

Neither Dave or Chris (or Sam) would have sold me any SK lenses to pair with the 180 under 60mm. Also when I bought the 180 back with the DF Chris pointed out to me if I decided to go into tech, it would cost me more for lenses than if I bought 140 or 160 back. This is a fact.

When I bought the 28mm LS for the DF, Steve made phone call to me in China to remind me again, to make sure I knew I was buying a great 30mm lense, but as 28mm - well the corners will not be as sharp as the rest of the frame.

Also Rod Kulkas of Arca Swiss is 100% honest, 100% knowledgeable. Has given only the best of advice.

None of the above EVER me feel like I had stupid questions and always went out of their way to not just tell me things but explain the whys and wherefores.

Seems to me that either the dealers in Europe are either not knowledgeable or are more like order fillers. Although Paula of Linhof in England and Robert White have been very open in the few dealing I have had with them.

The limitations and the expertise of pairing lenses to senors is very logical to me. When I bought my Rodenstocks, it was very clear that if a 100 megapixel sensor comes out then there was no guaranteeing they perform as well as they do paired to the 80 MP back.

Personally I would never make this kind of investment without an honest dealer. Just like I would never buy a Ferrari from a used car lot.

With my experiences I find it an injustice that Steve from CI has to defend his Company.

I can not speak for Phase, as I have very little dealing with them directly in Denmark (although the few dealings have been positive). Cambo, and Arca Swiss, and even with the local Phase and Canon offices, this is as good as it gets.

Personally I am proud to consider the people I have named above as friends. They helped me make the right decisions, and also taught me things. Just as I have learnt from the posts on GetDPI forum

Phil
 

Lorenz(X)

New member
hi there,
first of all,there is a lot of useful information here.thanks for that! since i am very interested in the cambo actus,maybe even more so. but on the other hand,the thread has gone in a direction wich has nothing to do with the actus any more (or at least not more than with any camera you can mount a digital back and large format lenses to.) and too much with not named dealers that might not be perfectly knowledgable or honest. of course there are dealers like that. but on the other hand,for everyone investing 50k into a system,getting information,and as much as possible,is not only recommended but a must. for me this whole crosstalk thing is completely new since i am not a digi-back shooter. i am using a mirorrless camera,and not even a full frame one ;) but for me,the actus makes perfect sense. so i appreciate what you are telling us torger,but on one point specifically i have to disagree wholeheartedly: the actus does not only have the possibility to use digi-backs and lf lenses. my intended use is to use my fuji camera and m645 lenses,wich are retrofocus and go down to 35mm, for landscape with the ability to use tilt and swing in combination with the tilt and shift mostly to get more resolution and a broader angle of view. i don´t know yet how much movement will be possible,of course i hope it will be as much as the image circle allows,but just to test that i will check the combination for myself. i was contacting calumet in germany,they gave my number to their specialist for cambo and he will be visiting me at home probably next week to get the chance to try the camera out myself. i think of this as really really good service,and since there are quite some experiences with these leses and many different kinds of cameras with the use of adapters by mirex or kipon,wich offer tilt and shift as well i think and hope i will not face to many problems. maybe i can not use all movements to their extremes and still get perfect results,but this is pretty unlikely to do in every-day use anyway. what this means for me is that i am absolutely super glad that cambo decided to get the actus to the market! for me this is a dream come true. i sincerely hope that problems like crosstalk will get addressed in future digi back designs,and i really think this is mostly up to the producers of those and not to the companies wich build the cameras in between the backs and the lenses. there are so many possibilities to combine different kinds of equipment that you can always find something that will not work,they could all just as well simply stop producing anything then! but of course,if someone tells you that you could just use back x with camera y and lens z,takes 50grand and you find out yourself that the results are garbage, i would be pissed too! but as long as this has not happened,and even on the contrary,dealers are trying to help with solutions that will work,we are really not in the position to complain i think! i do hope that there will be a really good live-view capable digital back that has no problem with crosstalk,cause you never know... in the future i might be tempted to get one for the actus that if not total junk (wich i do not think it is..) i will be a proud owner in a week or two! :)
lorenz
 

jlm

Workshop Member
well...given the problems using wides with x50 backs and the limitation of getting a wide rodie or sk to fit, coupled wiht he crop factor of the x50; what is the resulting wide angle ability of the actus/x50?
 
Last edited:

yaya

Active member
The majority of the members on this forum shoot landscape and therefore are predominately interested in wide angle photography. However please note that at Photokina the Cambo Actus was shown with a Schneider 80mm lens and when I tested it it performed beautifully with the Credo 50. We (Cambo and me) had some further discussion on potential uses for this camera and what can be improved or tuned to accommodate those.
Personally I see it as a fantastic replacement for many of the old studio view cameras, especially for shooters who now do more location work than they used to do. Think food for example and look at it as a very capable, compact and reasonably priced T/S solution. You can use your old LF lenses on a camera that is about 1/5th of the size & weight of your old P2 and that is in reality much more rigid and precise than any 4x5.
The new Arca-Swiss is another take on this concept and it even adds electronic shutter options, both focal and leaf.

IMO these new products offer a lot of versatility for existing and new MF users and not only for landscape photography.

Yair
 

torger

Active member
I've seen people buying this for food photography and similar, ie longer lens photography and there it will be fine. Personally I don't think it's a good design to drop rear tilt/swing if it's intended for product photography. A key advantage of using a studio view camera instead of a boring DSLR setup with a tilt-shift lents is that you can keep the lens still and do movements on the back. The Actus design in terms of movements is to me suitable for landscape and architecture type of applications -- so that is how I interpreted this product, but current lens+sensor combinations does have limitations there and people still seems to be interested in it, but then for longer lens photography where I personally would choose a different design. But that's me...
 

torger

Active member
As there's a huge subjective factor when it comes to color cast and crosstalk and a huge variation in how people shoot with their lenses (ie how much they shift), there can be a mismatch in expectations. It's a bit like asking if a lens is sharp enough to allow Xmm of shift. My "sharp enough" is not necessarily the same as the next.

For example, from real images I've seen I would not use the IQ180 with an Rodie HR 32, too much crosstalk and microlens ripple for large shifts, but many others think it's an excellent combination, as they don't shift as much and/or have lower expectations on image quality. I think I'm a bit more picky concerning this aspect of image quality than the average MF shooter, but I do know of at least one user that actually cross-graded from IQ180 to IQ260 to improve image quality with the Rodie HR 32.

What makes crosstalk so treacherous is that it's 1) not reversible (not with currently available algorithms at least), 2) varying depending on sensor orientation, and 3) varying depending on scene content.

That is if you shoot with the best orientation (often horizontal) and in a scene with dull colors it can work drastically better than shooting in vertical orientation in a scene containing bright saturated colors.

As far as I can see those points have not been particularly well-known in the community. Anyone interested in the new CMOS backs and pushing the limits with tech wides should know about it and adapt their testing protocols accordingly.
 

Geoff

Well-known member
It may be important to keep a sense of perspective here (no pun intended). Whenever a new issue or design shows up, there is a tendency to see this new issue as central and critical and all other concerns fall off the page. The new Cambo and Arca offer some very exciting opportunities - shifting, tilt, flexibility and all this in a small package. I think (?) possibly the Linhof Techno started this, and its interesting to see other camera makers get into this area. Good for all of us.

There are major issues to be dealt with at this scale of camera (small, tech'l) including lens design, rigidity, parallelism, flexibility, and overall build quality. One discussion could be on just usable lenses of different length - matching lens quality to sensor size. Then there is a subset, a discussion about usable shift.

For extreme shifting with wide angle lenses and certain sensors, we can now look to the crosstalk issue, which as Torger notes, varies in import by the user, the lens, the scene, the orientation, even the colors, not to mention individual taste. Its an interesting point, glad its been raised.

However there are lots of things (many) to be done with these cameras before encountering it as a problem. Perhaps its one of, say, 30 different issues to be considered? Alls to suggest that we don't fall into the 'internet' trap of "the latest issue is the most important" and let all other concerns fall to the wayside. There's a lot of neat things happening with these new cameras.
 
Last edited:

Guy Mancuso

Administrator, Instructor
It may be important to keep a sense of perspective here (no pun intended). Whenever a new issue or design shows up, there is a tendency to see it as central and critical and all other concerns fall off the page.

The new Cambo and Arca offer some very exciting opportunities - shifting, tilt, flexibility and all this in a small package. I think (?) possibly the Linhof Techno started this, and its interesting to see other camera makers get into this area. Good for all of us.

There are some major issues to be dealt with at this scale of camera (small, tech'l) including lens design, rigidity, parallelism, flexibility, and overall build quality. One area of this discussion includes usable lenses of different length. Then for the all of these, there is usable shift.

For the combination of extreme shifting and wide angle lenses, Torger has directed attention to the crosstalk issue, which as he notes above, varies in import by each user, the lens, the scene, the orientation, the colors. Its a very interesting set of issues, however there are lots of things (many) that one can do with these cameras before encountering it. Alls to suggest that we don't fall into the 'internet' trap of "the latest issue is the most important" and all others fall to the wayside. There's a lot of neat things happening with these new cameras and many good things incorporated.
Totally agree. Frankly I ignored and still ignore all the talk of the A7r shutter shake. Okay it has it but I just find ways around it like I do with any system. Does not make these systems anything less than what they are it just makes you have workarounds in place to apply. That has been the story with all of photography since day one. That will not change regardless of the tech involved, there will always be something to deal with. Okay I'm going to run out and shoot more of this Credo 50. I'm liking this back, I think it has some real potential in many areas of photography. Having live view and high ISO ability alone makes this very interesting. It has CMOS tendency but it also has a lot of DR to work with. I noticed it tends to have high highlight values but not losing detail either. I'll talk of this later. Typical CMOS stuff but the IQ is outstanding.
 

synn

New member
Hello all,

Getting back to the Actus, I am doing some (Very early stage) research about a tech camera platform I could use my Credo 40 on. Wide angle capability is a must. So far,t he Arca RM3Di seems to be winning. My question is, would the Actus be able to support the same lenses for the Credo with at least as good performance? I am looking at 24/ 28mm lenses at the wide end.

Also, if I use my M645 lenses on this camera, how would I be able to control the exposure, as the camera itself has no focal plane shutter?

Any inputs would be welcome. Thanks!
 

torger

Active member
The Actus should support the same lenses as the Arca RM3Di, however you won't have the same possibility to focus as precise directly by dialing in a distance. You'll focus on live view. If that's important to you or not is up to you. If you shoot closeups and product having a distance scale won't be that meaningful, it's most usable in architecture (where you have a laser distance meter to measure distances) and also useful in landscape even without a laser distance meter (the good ones work okay outdoors too though) when you can dial in things like hyperfocal distance very precisely. The RM3Di has the optical distance meter too as an accessory if you prefer that (e-module Cloud).

The Arca RM3Di lens mount is expensive, just as Alpa's, but an added bonus should be that you get a calibration and guarantee that the lens is performing up to spec.

As far as I know lens-board mounted lenses do not get the same treatment (they're just mounted as-is directly from Schneider/Rodenstock), on the other hand if you discover that a lens is off you can send it in to get it re-aligned. I have not needed to do that with any of my seven Digitars of which six was bought second hand. I do suspect though that my 47 is a tiny bit off and could perform a bit better if re-aligned, might send that in.
 
Top