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Author Topic: High resolution, scaled focus dial for the Actus??  (Read 2534 times)

Hening Bettermann

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High resolution, scaled focus dial for the Actus??
« on: May 07, 2017, 12:56:10 PM »

Hi!

would any of you see a possibility to replace the focus knob of the Actus by a wheel with a dial that allows me to read say 0.05 mm of focus travel?

Well my purchase of an Actus is not immediately imminent. But if I can not get something like this, I will consider the camera unsuitable for focus stacking and drop even the thought of it.

Using the lens helicoid is not an option, because the point in getting the Actus would be to get the Schneider lenses for it in the not too long run, and to be able to use my Apo Fujinon 180 and Apo Ronar 300.

Good light!

BobDavid

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Re: High resolution, scaled focus dial for the Actus??
« Reply #1 on: May 07, 2017, 03:00:04 PM »

As far as I know, the answer is no. I used an Actus for a few years. Great camera. But it has its limitations: The absence of micro focusing gears with a precise scale for focus stacking and a lack of finer gearing for swings and tilts. A hard detente for swings would be a welcome feature. The amount of swing and tilt movement required for mft and 35 FF are often a fraction of a millimeter. ... I used the Actus as a platform for copy stand photography and as a field camera. It is a good performer in the field, if you are careful to magnify live view for critical focus and for swings and tilts. It's an excellent field camera so long as you are methodical about setup and taking test frames to ensure adjustments are tuned for optimal results. It's a wonderful camera for stitching both in the field and for copy stand work.
« Last Edit: May 07, 2017, 03:19:46 PM by BobDavid »
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Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #2 on: May 07, 2017, 05:13:46 PM »

Thank you for your reply, Bob. - Strange that nobody seems to lack this - or says so.

I should have made it clear that I'm talking about the Actus Mini for the a7r2, maybe the GFX later. If you say that you have used it for years, you are obviously referring to an older, "normal" Actus.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #3 on: May 08, 2017, 04:06:52 PM »

Do you think (something like) this could be used?

http://www.farnell.com/datasheets/2047529.pdf?_ga=2.26620794.613482938.1494246817-1540928351.1494245462

Maybe it could be mounted instead of the focus knob? That alone would do for focus stacking.

But maybe we could even get Scheimpflug by the numbers? If we could
-mount this device instead of the tilt and swing knobs as well
-team up (as kick starters?) to hire a genius to write an iPhone app that
--translates the focus numbers to millimeters, and the the tilt and swing numbers to degrees
--allows us to manually enter the on-screen distance between 2 focus points
--translates these points to distance-on-sensor
--calculates the Scheimpflug angle from this distance and the focus difference 
??

Another question: The Farnell data sheet says "vernier reading". I don't hope this is true, and I can not see a Vernier scale, just a single number in the window. ?

alan_b

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Re: High resolution, scaled focus dial for the Actus??
« Reply #4 on: May 08, 2017, 06:25:11 PM »

Depending on how much of a DIY project you're up for, a follow focus knob could be rigged w/ gear reduction.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #5 on: May 08, 2017, 07:53:03 PM »

Thanks for your reply, Alan. As far as I can see, the follow focus system addresses a different problem, is designed to work directly on a single DSLR lens, does not provide a scale and is indeed a major rig. What is needed here is not primarily a gear, that works on one lens, but a precision-scaled knob that replaces the focusing and tilt/swing knobs of a view camera.

alan_b

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Re: High resolution, scaled focus dial for the Actus??
« Reply #6 on: May 08, 2017, 08:11:10 PM »

Sorry, I wasn't talking about using a follow focus kit as-configured, but rather as a starting point or idea for modification.  Some fabrication work would be necessary since I don't think there's anything on the market that does exactly what you want.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #7 on: May 09, 2017, 08:20:53 AM »

[...]  Some fabrication work would be necessary since I don't think there's anything on the market that does exactly what you want.

Indeed, but the the question is just how much machine work is required. Can you specify what you think is talking against my plan of "just" mounting this scaled radio knob instead of the existing focussing knob? (Maybe if needed exchange the shaft as well.)

Michael Erlewine

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Re: High resolution, scaled focus dial for the Actus??
« Reply #8 on: May 09, 2017, 01:54:30 PM »

I don't know about adding a dial, but I use this on my Novoflex Castle-L & Castel-Q racks. It very much helps to make smaller movements.


https://www.bhphotovideo.com/c/product/849714-REG/Novoflex_CAST_FINE_Fine_Focusing_Extension_Handle.html
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Michael Erlewine
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Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #9 on: May 09, 2017, 02:06:12 PM »

Thank you for your comment, Michael. - I hope the movement of the Actus itself is fine enough, even though I have no experience with it. The dial however is the crucial point for me when making a focus series. I have equipped my lenses with a millimeter scale glued around the barrel. This is what I need to replace.

alan_b

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Re: High resolution, scaled focus dial for the Actus??
« Reply #10 on: May 09, 2017, 02:55:18 PM »

Indeed, but the the question is just how much machine work is required. Can you specify what you think is talking against my plan of "just" mounting this scaled radio knob instead of the existing focussing knob? (Maybe if needed exchange the shaft as well.)

Not sure, looks like it would require some shaft adaptation and a way to fix the surround in place.  You'd also want to make a custom scale that measures mm of movement of the standard.  I don't have an Actus to know how the knobs are attached.

Just replacing the Actus knob with a larger diameter one might be pretty simple and give you more control - like Michael suggested.  You could add a pointer and wrap a printed/calibrated mm scale around the outside of the knob to give you some repeatability.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #11 on: May 09, 2017, 04:17:45 PM »

> You could add a pointer

That is exactly one of the problems - how to get a reference point. For my stone age Arca Swiss, I had had machined such large focus wheel and wrapped a scale around it, where 1 mm on that scale equaled 0.1 mm of focus travel. Looking at photos of the Actus, I see no space for such wheel nor for a way to fix a reference mark. That's why I thought the combination of that radio knob with a little iPhone app was so smart. For the focus stacking alone, a calculator would do instead of the app. It is all about that shaft adaption. In the end, only Actus knows the answer. I just wondered if anyone might know something if such radio knob could work at all, even if the shaft adaption could be fixed.
 
--oh well, Michaels idea of extending the shaft of the focus wheel might create space for a large wheel. But it leaves the problem of the reference mark.

> You'd also want to make a custom scale that measures mm of movement of the standard.

With the radio button, I see no way of changing the scale on the button. For focus stacking alone, I don't need the focal difference spelled out in mm. Just any scale will do, as long as it's precise enough.

And if it comes to Scheimpflug, one will want something like an iPhone app anyway, so that app could as well translate scale values to mm and degrees, respectively. No need to change the physical scale on the buttons.

It's all about the shaft adaption. Or if the radio buttons are strong enough to move the standards.


 

BobDavid

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Re: High resolution, scaled focus dial for the Actus??
« Reply #12 on: May 09, 2017, 10:01:29 PM »

Thank you for your reply, Bob. - Strange that nobody seems to lack this - or says so.

I should have made it clear that I'm talking about the Actus Mini for the a7r2, maybe the GFX later. If you say that you have used it for years, you are obviously referring to an older, "normal" Actus.

It's the same camera., and I used it with an A7r II and an Olympus E-M5 II for multi-shot applications. I suppose you could paint or etch a tick mark on the focus knob or mount a heliocoid to the lens for added precision.
« Last Edit: May 09, 2017, 10:39:52 PM by BobDavid »
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Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #13 on: May 10, 2017, 05:38:38 PM »

> I suppose you could paint or etch a tick mark on the focus knob

Bob, the knob will need a reference mark outside itself! If one wants to use it without the built-in scale, where the zero value is the reference.

> mount a helicoid to the lens

Well that is exactly what I hoped to overcome: being restricted to lenses that have a helicoid of their own - and even if they have: that's (the weight of) a helicoid for every lens. And adding a helicoid to a lens in post - well, I'm not sure if Schneider still offers this option for their lenses. And for the shortest focal lengths it will not be possible. As said, one main argument for the Actus is the Actars.

It looks like the shaft adaption is the hub, and that I need to ask Cambo.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #14 on: May 11, 2017, 09:40:18 AM »

Jeffrey Goggin, who is not a member on this forum, (but obviously a reader), has mailed this  to me off-list and authorised me to quote him here. He has a solution for the focus, if not for the Scheimpflug. The focussing is the most important part for me, since with my typical subject matter, Scheimpflug would not help anyway. Thanks Jeffrey!

"As it happens, I have an Actus that I use with a Sony A7R body and was just this afternoon experimenting with something that serves the function as you propose, but is implemented somewhat differently.
Instead of measuring focus changes via the rotation of a knob, I attached a dial-indicator to camera body and measure focus changes off the back of the rear standard, as shown in the photo below:

Although this is only a temporary setup that I created in less than five minutes using parts I already had on hand and then clamped it onto the Actus body, a more permanent setup should not be too difficult to fabricate.

This is because the bottom of the Actus mounting rail has an Arca-compatible dovetail machined into it, so you can attach the dial-indicator assembly to an Arca-compatible clamp and quickly install and/or remove it, as necessary.

Although the Actus' focus knob is (IMO) geared a bit too quickly for fine-tuning focus at this level of precision, if one turns it slowly and carefully, it is easily possible to make adjustments of less than .001" over a range of 1", which is already twice as fine as the .05mm you need."

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #15 on: May 11, 2017, 11:50:48 AM »

Bob,

> A hard detente for swings would be a welcome feature

I just discover that not only is there no hard detente - also the swing scale is a joke. So how do you EVER nail an exact perpendicular position of the front standard? And since there is no arrest either, the swing may accidentally change position during transport, in other words you will have to check/re-adjust it before EVERY shooting! How do you handle this?
« Last Edit: May 11, 2017, 12:10:36 PM by Hening Bettermann »
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Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #16 on: May 11, 2017, 03:30:14 PM »

I have asked Jeffrey Goggin about this as well; I quote from his answer:

"The camera self-applying an unintentional swing movement has been an issue for me, as well as many other Actus owners, and I've pondered several solutions.

[...]

Initially, I started carrying a small, telescoping "snap gauge" with me and used this to reset the swing movement to a neutral position by using it to measure the gap between the front and rear standards (via the bellows mounting plates) on either side of the rear lens element.
It doesn't really matter what the actual measurement is, only that it's equal or very close to equal on both sides (which means there is no unintentional swing movement being applied, because the difference between the the measurements will be zero when the bellows mounting plates / front and rear standards are perfectly parallel to each other.)
With a careful, practiced touch, this can be determined accurately enough for my purposes merely by feel, as the drag on the snap gauge will have equal resistance when it's pulled between the two bellows mounting plates, as shown in the photo below.
To equalize the drag resistance of the snap gauge side-to-side, one merely turns the control knob for the swing movement very slightly in the appropriate direction and then checks the results with the snap gauge.  In my experience, I can usually neutralize the movement within three or four adjustments, so the process doesn't take very long.  And because I photograph mostly at night, without very much light around, it can even be successfully done in the dark [...]
--foto1--

Although it's a minor nuisance, this process allows me to reset the camera accurately enough (typically to within ~.005") while I'm photographing in the field in just a minute or two.  When I later return home, however, I will reset it slightly more accurately using a micrometer caliper and by determining the actual measurements instead of by feel alone.
Ultimately, though, I decided that because I use the swing movement so rarely, that a better solution was to simply tighten the swing mechanism further, increasing its resistance to rotation.  This is easily done by tightening clockwise the adjustment screw located on the front side of the front standard (circled in red in the photo below):
--foto2--

It is possible to tighten the screw enough to effectively disable the swing movement completely and in my experience, when it's tightened to this extent, even a five-mile walk with my camera / tripod combo over my shoulder won't cause it to move noticeably..
Because I do occasionally use the swing movement, however, I generally leave it slightly looser than that, so the control knob can still be turned, but doing so requires significantly more effort than it did with the tension as set by the Cambo factory.
As a result, I do still occasionally have an issue with unintended swing being applied if my walk is longer than, say, three miles, but as I still carry the snap gauge in my bag, it's not a big deal to reset the camera in the field when necessary.  (FYI, with the tension left as set by Cambo, the swing movement would sometimes go out of adjustment within just a few hundred yards of walking, so a couple of miles represents a significant improvement.)
And although I personally don't have any problem with the tilt movement being unintentionally applied in a similar manner, if I ever do, it can be reset exactly the same way as the swing movement is, except the two measurement points will be rotated 90 degrees, so they're at the top and bottom of the bellows mounting plates instead of the sides.

So, to summarize, Yes, the design of the camera is such that the potential does exist for both the tilt and swing movements to be applied unintentionally while the camera is being used in the field -- FYI, so far, this has not been an issue for me whenever I use it at home -- and one must check the photos being taken very carefully to verify that it has not gone out of adjustment.  (Although it's not seen in the above photo, I hang a 7" diagonal, external HDMI monitor off the back of the Actus (via a bracket I fabricated that attaches to the bottom of the Actus mounting rail using an Arca-compatible clamp) which makes it much easier for me to see when the camera has gone out of alignment, as well as to focus and compose my photos in the first place.)
But even when the camera's swing and/or tilt movements do go out of alignment and requires readjustment, it's not that difficult to reset them in the field within a few minutes, provided you have a snap gauge (or some other type of simple go/no-go gauge) along with you.

[...]"

BobDavid

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Re: High resolution, scaled focus dial for the Actus??
« Reply #17 on: May 12, 2017, 01:31:48 AM »

> I suppose you could paint or etch a tick mark on the focus knob

Bob, the knob will need a reference mark outside itself! If one wants to use it without the built-in scale, where the zero value is the reference.

> mount a helicoid to the lens

Well that is exactly what I hoped to overcome: being restricted to lenses that have a helicoid of their own - and even if they have: that's (the weight of) a helicoid for every lens. And adding a helicoid to a lens in post - well, I'm not sure if Schneider still offers this option for their lenses. And for the shortest focal lengths it will not be possible. As said, one main argument for the Actus is the Actars.


I only used M39 enlarger lenses on the Actus. They are incredible--small, light, and reasonably priced. I've purchased a couple helicoids on Amazon. I just adapted a Rodenestock Rodagon APO 80mm F/4 N to a Sony A7r II. It works like a charm. The APO 80 enlarger lens is tack-sharp, shows virtually zero linear distortion and CA. Before I sold my Actus, I used a WA 60mm Rodagon, a 105mm El-Nikkor N, and a Rodenstock 135mm f/5.6.

I paid $35 for a helicoid. Amazon has several types. They are plastic, not machined. However, they are extremely workable. I've looked at the Actars. A few of them look similar to high-end enlarger lenses mounted on helicoids. You may want to consider trying ELs. The cost/benefit ratio is excellent.

I am keeping the enlarger lenses. The Rodagon WA 60  comparable to the APO 80mm. The EL-Nikkor 105 f/4 N is excellent, as is the Rodagon 135mm.  For the 105 and 135, I used extension tubes to extend the distance form the sensor to the lens. That was an inexpensive solution relative to buying components from Cambo.

As I've stated earlier: The Cambo Actus is a nice camera. However, it is fiddly when using swings. And tilt requires some patience and practice. After using the camera for a year, I was able to set up a shot in the field within five minutes. Not bad. If you are seeking total precision, perhaps a Sinar P3 is a good option. I'm sure the Cambo Ultima 35 is excellent. 

I give it an A+ for copy stand work.

As far as wide angle lenses go, the Actar 24mm is fine. I always used it at f/8 for optimum sharpness, contrast, etc. Here's a link to a review I wrote up on the 24: 24mm Actar Review
« Last Edit: May 12, 2017, 01:56:26 AM by BobDavid »
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Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #18 on: May 16, 2017, 04:38:15 PM »

Hi Bob,

I have been travelling and offline for some days, hence my delayed reply. So for now only a quick Thank You for your tips. I will explore them later.

Hening Bettermann

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Re: High resolution, scaled focus dial for the Actus??
« Reply #19 on: May 18, 2017, 02:47:04 PM »

Hi Bob,

I have thought about your suggestion of using enlarger lenses.

My thinking around Actus and lenses is this:

I am now using the a7r2, a good CY zoom (28-70) and 8 good primes (CY, Voigtländer, Nikon, ZF, Olympus). They are good now. But before long, the a7rx and/or the Fuji GFX will have 80-100 MP. Then, the lenses will be the limiting factor. Schneider claims that their Actars are built for 100 MP sensors. At the same time, they are comparatively light, since they are not so fast. And the image circle will allow for a little movement. So I think in the not so far future, Actars will be the lens line of my choice - or at least desire... If I had an Actus, I could *gradually* buy into this line, using my 35 mm film era primes for the rest. Also, I could use some longer LF Apo lenses I already have.

In this scenario, I don't think I will buy into enlarger lenses.

View cameras like the Sinar P3 or Cambo Ultima 35 are out of the question for me because of the weight.

Anyway, thank you for your suggestions!
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