Luminous Landscape Forum
Equipment & Techniques => Medium Format / Film / Digital Backs – and Large Sensor Photography => Topic started by: BernardLanguillier on January 30, 2016, 03:41:36 am
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Hello all,
A question for Actus DB owners.
How easy is it to reach critical focus with CMOS backs on the Actus with tech camera lenses such as the 40mm and 90mm lenses?
Thank you.
Cheers,
Bernard
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Hello all,
A question for Actus DB owners.
How easy is it to reach critical focus with CMOS backs on the Actus with tech camera lenses such as the 40mm and 90mm lenses?
Thank you.
Cheers,
Bernard
I don't own an Actus but worked with them quite a bit...focusing, at least with IQ & Credo is really easy and accurate.
HTH
Yair
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Thanks Yair!
Cheers,
Bernard
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I believe you should edit the O/P as Actus is completely irrelevant to a back's focusing ability... I don't have a Cmos back either, but from what I hear from friends that do own Hasselblad Cmos backs (both H5 & CFV), LV is as easy and accurate as with modern Cmos DSLRs like the ones you own... I don't find a reason why it should be different with P1 or C
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How easy is it to reach critical focus with CMOS backs on the Actus with tech camera lenses such as the 40mm and 90mm lenses?
Not all "CMOS backs" have the same quality of live view.
With the IQ and Credo you can expect smooth, continuous, high frame rate live view in both bright light and lower light situations.
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I believe you should edit the O/P as Actus is completely irrelevant to a back's focusing ability...
It's quite relevant. The precision of the gearing, and the build quality of the standards influence the ability to do fine focus at high resolution. For instance a great live view coupled with a beat up Toyo is not especially easy to focus a 40HR with.
If I could suggest... this question is best answered by people who have actually used any of the equipment involved in the question.
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I have both an Actus and Leaf Credo 50 CMOS back. Its a snap to reach critical focus and the Actus has changed - for the better - my shooting experiences. Love the camera..... I have seven Schneider Digitar's from 35XL to 180mm that work like a dream with this camera. Rody's would focus just as easily.
Victor
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It's quite relevant. The precision of the gearing, and the build quality of the standards influence the ability to do fine focus at high resolution. For instance a great live view coupled with a beat up Toyo is not especially easy to focus a 40HR with.
If I could suggest... this question is best answered by people who have actually used any of the equipment involved in the question.
Still, if a back is focusing as good as it gets, it will do so with any view camera, a camera can improve or not the focusing ability, but the combination with a back is completely irrelevant with respect to other (better or worst) view cameras, "as good as it gets" with a back, is ...as good as it gets! ...and no! you can't suggest people posting out of their own experience only... what they hear out of (pro) friends that have own experience and have shared that experience is also relevant as it is still reliable information. After all, that's the purpose of forums... to share reliable information that could be valuable to others.
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As many of the tech lenses is f/5.6 wide open (the Rodie 40HR is f/4) it's naturally a bit more difficult to peak than Zeiss Otus 55 at f/1.4. It's easiest to peak focus if you in the same view can see both in-focus and out-of-focus areas, and the likelihood that you do that increases the larger the aperture is.
But there's many other factors as mentioned, live view frame rate, how sharp live view renders, the screen on the back, and the gearing on the camera body, how rigid the body is. Everything adds up to the total experience.
Of course it also makes a difference if you shoot at f/4 or f/11-f/16 as the smaller apertures mask focusing errors, and how picky you are when pixel-peeping the result. You'd probably shoot at least f/11 with that type of lenses which gives you some margin.
There's also a bit about training. I'm used at focusing with ground glass thus I can work with almost anything :). The more you use the camera the better you will become at handling tough conditions. Live view becomes worse the darker it is for example, and with training you can handle darker and darker conditions.
I've noted that what's "easy" to one person can be really difficult to another, so it will be hard for you to get an accurate answer to the question. My expectation is that you will feel that it's a bit more difficult than you're used to from your DSLR, but still not so difficult that you become bothered by it. I haven't used your DSLR combination or the Cambo combo side by side though so I cannot say anything for sure.
If you're aiming at an CFV-50c you should know that the live view is not the same quality as an IQ250. I don't know the details of what differs (I would guess lower framerate and worse at handling difficult light conditions), only that it's something you should look into before buying.
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Here's a video showing CFV-50c live view frame rate in ISO3200:
https://www.youtube.com/watch?v=6A_B22lJ9Wg
And a focusing example:
https://www.youtube.com/watch?v=PCCzEs7rKZc
Although as you can see the frame rate is not super (it's faster in ISO100) I don't think you would find it problematic. I don't know which lens they've been using in that video, it's a Linhof Techno though, and probably a Rodenstock Digaron lens, could be a 40HR judging from the field of view.
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Here's a video showing CFV-50c live view frame rate in ISO3200:
https://www.youtube.com/watch?v=6A_B22lJ9Wg
And a focusing example:
https://www.youtube.com/watch?v=PCCzEs7rKZc
Although as you can see the frame rate is not super (it's faster in ISO100) I don't think you would find it problematic. I don't know which lens they've been using in that video, it's a Linhof Techno though, and probably a Rodenstock Digaron lens, could be a 40HR judging from the field of view.
Anders... you are under serious danger to be attacked by Doug on the reliability of your (valuable IMO) post, because...
1. You don't own an Actus with Cmos back :)
2. The camera isn't an Actus... :D
3. The back in both videos is not one he sells, but same sensor Hasselblad... ;D
According to Doug, reliable experience out of others that is posted by forum members shouldn't count... ;) (especially if it is equipment he doesn't sell - my conclusion!)
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Credo50 with ActusDB user. No problem focussing, in my case on a monitor. The Actus is a lovely little view camera, just 1.3 KG without lens and back. Live View is a massive improvement on the CCD backs. The only thing I don't like about the Actus is the awful, ugly bellows, completely disproportionate in bulk to the rest of the camera. So I machined some adapters and I now use the synthetic (long) Arca bellows instead (not the leather ones that look saggy and sad). If Cambo is seeing this, please change the bellows and you'll turn a monster into a little beauty:)
Since Arca bellows are quite expensive, another option is to have them made bespoke, they'll be a cheaper then machining adapters.
Edward
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Bernard,
Not all "CMOS backs" have the same quality of live view.
If you're aiming at an CFV-50c you should know that the live view is not the same quality as an IQ...
https://vimeo.com/149422712
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Bernard,
https://vimeo.com/149422712
I believe that he states on the O/P that he is looking for "critical focus accuracy" not for possible differences in frame rate... I would care about LV's other aspects of quality than "critical focus accuracy" if I wanted LV for video, but for "critical focus accuracy" all Cmos MFDBs offer superb accuracy and surely more than everyone that has used with CCD backs of the past would ever dream of... (other than a Sinarback with LC shutter that also offers superb LV focusing accuracy but only tethered for more than 10 years now...).
Never the less, the CFV is running for the same price as a P645Z, offers dead on LV focusing accuracy and the best color accuracy out of all makers thanks to Hasselblad's new (superb) calibration method....
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Agree that the CFV has more than ample frame rate capability for accurate focus. However, the OP asked about a combination of a/any CMOS back and the ACTUS which leads me to believe that he was concerned about the mechanical accuracy of the ACTUS. From my point of view I would like the geared focusing to be even finer.... but I am nitpicking as I have never had an issue with how it is currently made. The front standard is very accurate in the '0' positions and all of the tolerances seem very tight. I highly recommend the long bellows and the long rail if intentions are to use any lens longer than 72mm. I also recommend to purchase the DB+ version as it comes with a slightly longer rail than the standard DB. It is a lovely camera that I wish I had purchased long ago. Schneider lenses in Copal 0 are still available at demonstrable savings over their mounted counterparts in either Cambo or Alpa flavors.
Victor
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I've been using the Actus DB+ and IQ150 with Rodie 32 & 70 HR lenses for a while. Focusing with LV on the IQ back and Actus is a complete breeze and very very easy. Ditto dialing in tilts etc.
One recommendation I have is to lock the controls once focus. Rise or tilt is dialed in. I wish there was a lock on the tilt control.
I agree with Victor that a slightly finer gear ratio would be useful at times. Agreed also on the bulky bellows which could be somewhat smaller and easier also to pack.
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Thank you all very much for your detailed and very useful answers.
The Acts itself was indeed my main concern and I am happy to read that it seems up to the task.
I'd want to use it with a 90mm lens, so thanks also for the rail length piece of advice. On this, is the rail of the DB+ version long enough or is there a need to order long rail even with a DB+?
Cheers,l
Bernard
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You wouldn't need a long rail with either the Actus DB or DB+ with the 90mm lens. The standard one will be fine.
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The rail that is included with the DB+ should give you enough length for normal use. However, if you want to get close (1:4 - 1:2) then the longer rail is necessary as is the longer bellows. If you ever shot one of the pancake cameras you will find that close focus on the Actus is liberating on a comparative basis. I recommend the longer bellows under all circumstances regardless of rail length.... Make sure you check the bellows for leaks - I had one that had a light leak. There was a faint contrast difference in images when I was comparing the Actus to my Alpa (camera alignment). Under further testing I found a significant leak.
Victor
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Still, if a back is focusing as good as it gets, it will do so with any view camera, a camera can improve or not the focusing ability, but the combination with a back is completely irrelevant with respect to other (better or worst) view cameras, "as good as it gets" with a back, is ...as good as it gets! ...and no! you can't suggest people posting out of their own experience only... what they hear out of (pro) friends that have own experience and have shared that experience is also relevant as it is still reliable information. After all, that's the purpose of forums... to share reliable information that could be valuable to others.
The problem is not achieving focus at a certain point of one's choosing but getting perfect edge to edge focus and for that the camera better have perfect alignment of the lens and back. Any slight twist or misalignment will result in uneven focus across the image plane. With large formats like 4x5 film or larger that was rarely an issue because it required larger misalignments to become destructive but with smaller formats like the relatively small digital sensors and short focal lengths even a miniscule misalignment will cause serious issues.
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Slightly off topic: I am using an Actus with an Oly EM-5 II. It's very easy to focus. As an aside, the Actar 24mm lens is a bargain. At f/8 it is tack sharp.