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Thread: Shooting with the CAPCam

  1. #1
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    Shooting with the CAPCam

    Ok, so this evening I decided to have my first go at getting my head around how to use the CAPcam.

    Be gentle with me - this is very early days...

    For those who are not familiar with this camera - and it's probably pretty much everyone since I believe there are literally only a handful of these out in the wild right now - it's a fully computer controlled view camera.

    GFAE, who make the CAPcam, have a website here where you can get some more information about the camera.

    To be honest, I should probably have held off writing up anything about it until I understand how to use it better myself - I've forgotten a lot of what I learned in Schaffhausen last Tuesday already (sorry Rolf!), but there has been quite a bit of interest from people since I posted about the fact I've just picked one of these up, and I thought my initial simple test would be worth sharing since it demonstrates one aspect of the basic functionality.

    Also, just writing this helps me get my head around the concepts

    Here's the set-up:



    Lens is the Schneider 120mm, back is my trusty IQ180.

    I'll spare you more photos of the set-up. What you can't see in that picture is that the lens has a Schneider electronic shutter.

    Cabling wise (can be complicated to get your head around this), power goes to the shutter control box; shutter control box controls the shutter; shutter control box is connected to the camera through a ribbon cable; to the flash via a sync port; to the computer via USB; and to the digital back via a sync cable. Finally, the back is connected to the computer over firewire.

    There are other ways to set up the cabling (for example, the back can be powered off the camera, and with a USB connection from the back to the computer), but for my kit (old MacBook Pro with firewire), this is the simplest way to do it.

    I didn't have a lot of time this evening, so wanted to keep the learning curve fairly simple, so set out to achieve just one thing.

    The subject is the 5x5x5 Rubik's cube on the shelf. Roughly angled edge on to the lens.

    The self-imposed challenge: How quickly can I change from having the focal plane aligned along the left hand face of the cube, to having it aligned along the right hand face of the cube?

    I honestly have no idea how long this would take to do manually - I'd be very appreciative of some input from those with experience of product photography, since this is a new area for me.

    I won't bother sharing the images themselves, since the interesting stuff is actually in the screenshots of the CAPcam software.

    A few things to note -

    I did this roughly - wasn't looking for 100% accuracy. I wanted to try to refresh my mind about some of the basic concepts.

    I was actually triggering the wireless flash manually - I didn't have a cable to connect the transmitter to the shutter box - hence the 1 second shutter speed.

    There is a LOT of information that the CAPcam software gives you about the set-up of the image. I won't go into all of it now, but one thing worth appreciating is that the software does not work on the lens tilt and swing angles that we would be used to thinking about - it works on the focal plane tilt and swing angles relative to the sensor plane. To me, this is a MUCH easier concept to work with, since it's directly related to the end result that you are after. You never have to think "what lens tilt do I need to get the desired focal plane angle I'm after?"

    Here's a screenshot from the CAPcam software for the shot where the left hand face of the cube is in focus:



    The red, green and blue markers are what are important for this test - ignore everything else for now. On the right hand side you'll see a table that gives the distance that represents the distance from the sensor that the point in the image each marker is highlighting is. If the three points highlighted are all in focus, then the three points define the plane of focus.

    What I did between the two shots was this - I dragged the green marker over to the far edge of the right hand face of the cube. Since the cube is (roughly) edge on to the sensor, the distance of the far left edge and the far right edge should be (roughly) the same.

    As you drag a marker across an image, the software recalculates (continuously, in real time) how far away that marker is from the sensor - on the assumption that it is still on the focal plane.

    So once I placed the marker on that right edge of the cube, the value for the green marker in the table was a lot lower than it was previously. This makes sense of course since dragging it to the right of the image would bring it closer to the sensor were it to be dragged along the focal plane. I then simply overwrote the computed value with the SAME value that it had prior to moving it.

    Since I didn't touch the red or blue markers, nor alter their values, the distances to the three markers should now be defining a focal plane that runs down the right hand face of the cube.

    Here's the second shot:



    Time for me to redefine the focal plane before hitting the capture button for this shot?

    2 seconds.

    Very early days for me with this camera, but I will continue to update this thread over time as I get my head around it better, and (hopefully!) become more capable with it.

    Kind regards,


    Gerald.
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  2. #2
    Member Miller's Avatar
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    Re: Shooting with the CAPCam

    Makes a nice change from shooting brick walls, doesn't it?
    But really, a very impressive piece of technology.
    Thanks for sharing!

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    Re: Shooting with the CAPCam

    Gerald, is the software using some kind of phase detection to focus?

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    Re: Shooting with the CAPCam

    Quote Originally Posted by jagsiva View Post
    Gerald, is the software using some kind of phase detection to focus?
    Hi -

    No. It's important to understand that there is no auto-focus (in the traditional sense) involved at all.

    Broadly speaking, what you do is this (if I've got it right - will hopefully have some practice on this tonight) -

    1. Estimate the distance to a point on the focal plane that you ultimately want to establish.
    2. Deliberately set the focal plane tilt and/or swing angle(s) so that the plane will cut through the focal plane you ultimately want.
    3. Take a shot.
    4. Set two of the markers on points in the image (on your desired focal plane) where focus was actually established.

    If you think about these two points, they both will contribute to defining where your final plane of focus will be, but, crucially - because they are actually on the plane of focus of the shot just taken - the camera will know the exact distances they are from the sensor.

    5. Now position the third marker somewhere else in the image that you want your desired focal plane to intersect with. This point will - in your current image - of course be out of focus. You need to enter into the software the distance this point is from the sensor. Typically, this is pretty easy to estimate given you know the exact distance of the two other points.

    6. Now take the second shot.

    If you got your distance estimate exactly correct, then all three points will be in focus, and you have achieved your desired focal plane. If your estimate for the distance to the third point wasn't exactly correct, it's not a problem - just move it to a new position in the second image that is both in focus, and on your desired focal plane, and take a final shot.

    There are, I believe, at least two other ways to achieve focus which I need to get my head around and will share later.

    A good video demonstrating the above method (but with older software) can be found here -

    https://www.youtube.com/watch?t=99&v=CcVtFOSHnFs

    Kind regards,


    Gerald.

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    Re: Shooting with the CAPCam

    Just to add, the crucial bit to understand in that video is at around the two minute mark when the green marker is moved to the far end of the middle pen. Because in the immediately preceding shot, the focal plane was established to run through all three pens, when that green marker is moved, the software knows exactly where it was moved to.

    Let the software keep the distances to the red and green markers. They were in focus before, and you want them to remain in focus for the next shot.

    Now simply enter an offset onto the blue marker to tell the software that you no longer want the point in the image that it is marking to be in focus, and for the next shot the focal plane will now be rotated around the center pen.

    Kind regards,


    Gerald.

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    Senior Member malmac's Avatar
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    Re: Shooting with the CAPCam

    Thanks Gerald

    It is interesting to read about this from a user - rather than a marketing department. I look forward to further posts as I am sure others do as well.


    Mal

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    Re: Shooting with the CAPCam

    Another way to focus. As before, screenshots of the CAPcam software.

    This is basically witchcraft...

    A Benjamin on the shelf, enter a rough estimate as to the distance from the sensor, take the shot flat-on.



    Now. Grab those two purple markers and place them on the bottom corners of the bill. Then, grab the white vertical lines and drag them so that they run up the edges of the bill. Finally, grab the first yellow horizontal line and align it with the top of the note (this isn't strictly required, but can be useful for checking).



    Note that this is all done on the image of the first shot.

    Now - look at the dimensions towards the bottom right of the screen shot. 62.87mm by 142.3mm

    A $100 bill is actually 66.294mm on the short side.

    Hover the mouse over the yellow line in the table on "Next" (currently saying 1,000.0m). Use the scroll wheel to adjust that number until the distance between the two purple markers is equal to 66.3mm.

    And press the capture button.



    I'm not entirely sure what's causing the offset in the final image** - will check with CAPcam. Regardless, pretty clever stuff, no?

    Kind regards,


    Gerald.

    /edit
    ** Actually, thinking about it - I'm guessing it could be because I'm placing the markers and taking measurements off an area which is quite considerably out of focus. As before - I'm just trying to refresh my mind of the things I was shown at GFAE, so apologies if I've not got everything 100% right!
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    Re: Shooting with the CAPCam

    Gerald, thanks for taking the time, this sounds great.

    Wonder this could be done in a smaller package if the subsequent "gyro" settings were done manually, i.e. you take the initial shots and get some kind of settings given to you by the software and you dial these in manually on a similar mechanism that moves the lens board.

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    Re: Shooting with the CAPCam

    Quote Originally Posted by jagsiva View Post
    Gerald, thanks for taking the time, this sounds great.

    Wonder this could be done in a smaller package if the subsequent "gyro" settings were done manually, i.e. you take the initial shots and get some kind of settings given to you by the software and you dial these in manually on a similar mechanism that moves the lens board.
    It seems you could do the focus calculations in software - maybe with something like a cell phone to transfer initial optical axis geometry to the computer. Once the guides are placed on the shot and processed, transfer settings to the (manual) view camera. That would give you an added capability for rear movements, which I am not sure this does?

    Certainly, the integrated hardware is faster and easier to use than manual transfer of settings. That could justify installing a costly system for a pro studio. However, the really clever bit seems to be the user interface. Perhaps they will make that available to a wider market? After wasting hours fiddling with tilt and swing, I would be all over this as a software package. In the meantime, I look forward to seeing what the integrated system is capable of in Gerald's hands.
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    Senior Member dchew's Avatar
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    Re: Shooting with the CAPCam

    Jae Moon used to offer software that did this just for tilt using Numbers on your iPhone. He would ask what lenses you use and send you a file. You type in the position of things (height and distance) and it would tell you what tilt angle and focus distance setting. Much better than most calculators out there that do the opposite. But I'm using different lenses now and can't find him anywhere!

    Quote Originally Posted by cunim View Post
    It seems you could do the focus calculations in software - maybe with something like a cell phone to transfer initial optical axis geometry to the computer..
    How glorious a greeting the sun gives the mountains! - John Muir

    davechewphotography.com

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    Re: Shooting with the CAPCam

    Evening 3. Time to try shooting a watch.

    Getting the hang of it now. What I did here was what I find to be the simplest and quickest way of focusing - estimate distance; set tilt so the focal plane cuts through the surface of the watch; shoot; place the green marker on a point that is in focus, note the distance; move the focal plane by a couple of centimeters; shoot; place the red and blue markers on points in focus; manually change the distance to the green marker to what it was in the previous shot; shoot.

    Sounds complicated when written down, but it's almost second nature now, and very quick to execute.

    Then I did a focus stack of 3 images. Not sure if I mentioned this previously, but the system automates focus stacking perpendicular to the focal plane. Brilliant stuff.

    Excuse the filthy watch!

    17.02 degrees of tilt, 1.31 degrees of swing (remember - these are the angles by which the focal plane has been adjusted, not the lens)
    Magnification: 1:1.75

    Full frame -



    100pc crops -





    Basically accomplishing with 3 shots what would have taken around 40 had I used the Cognisys StackShot.

    I'm very, very happy

    Kind regards,


    Gerald.
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    Re: Shooting with the CAPCam

    That is pretty impressive!

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    Re: Shooting with the CAPCam

    Quote Originally Posted by jagsiva View Post
    Gerald, thanks for taking the time, this sounds great.

    Wonder this could be done in a smaller package if the subsequent "gyro" settings were done manually, i.e. you take the initial shots and get some kind of settings given to you by the software and you dial these in manually on a similar mechanism that moves the lens board.

    Even though CAPcam (in conjunction with the mobile power pack) can be used on location, it is designed mainly for studio use. Depending on the lens and its lens tube, image scales from 1:infinity to 1:1 or 1:3 to 3:1 can be done.
    At larger image scales, a large extent is necessary. This makes the camera that big.


    CAPcam's electronic drives not only do focussing. They also control tilt/swing and shift.
    During these operations the effective focal length of the lens changes. CAPcam automatically preserves the focal plane and the image center.

    Doing that manually with a view camera built on an optical bench, several knobs need to be readjusted every time (camera extension, camera orientation horizontal/vertical, tilt, swing, shift horizontal/vertical). Any of these adjustments has some tolerances which will be added along the whole chain (series mechanics).
    To achieve perfect focus with a high resolution digital back, lens position must be within +/-30um. Quite difficult!

    CAPcam uses a parallel mechanics where the error of a single drive is not added to other errors. They were averaged instead.


    Regarding your question, if a similar software could calculate the required settings which then could be manually adjusted:
    To be able to do calculations on an initial shot, also every setting applied to that shot must be known. The same requirements on accuracy apply here.

    I hope this explains, why this application cannot be run with manually controlled cameras.

    Kind regards
    Rolf Eigenheer
    GFAE switzerland (manufacturer of CAPcam)
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    Re: Shooting with the CAPCam

    Thanks Rolf, that explains a lot. Also great to have you directly contributing here in addition to the great effort already by Gerald.

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    Re: Shooting with the CAPCam

    My (main) watch back from a spring clean in Geneva. Obviously before winding it I had to introduce it to the CAPcam.

    0.75mm depth of field. With traditional focus stacking, this would have required around 50 shots to get the entire watch movement in focus.

    With the CAPcam? Just 5...



    Kind regards,


    Gerald.
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