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Thread: Questions about Alpa Ground Glass Use

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    Senior Member dchew's Avatar
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    Questions about Alpa Ground Glass Use

    Just got a bunch of fun stuff this week from Alpa. I've been using an STC since 2011, and find myself shifting and stitching much more these days. I bought the ground glass for framing, not focusing. I've tried using LV for framing but I feel rushed as the battery power drains... Also there is no way to see around the image for stitching.

    Although I've used a ground glass before on occasion, this is the first time I've owned one so I don't really have a routine developed. Some questions:

    How well do I need to protect it from dust and the elements? I would like to leave it mounted on the STC when in the backpack, but I don't have a way to cover the whole camera. Do I need to put it in a zip lock bag, or is that not necessary?

    The Alpa PGS comes with a 4mm grid but no other marks. I want to add corner marks for 54x40 and some shifted formats. I would rather mark the screen vs using masks so I can see what is around the image. Do I just get a fine point Sharpie and mark away? I'd rather not screw this up; I only have one chance!

    Loupes: I need some help with recommendations. I won't be using this for focusing, only framing, so coverage is more important than magnification. It would be nice to cover the 18mm shift each way, but that would be a huge loupe. So in order of importance:
    1. Coverage
    2. Size (taking this backpacking)
    3. Image quality
    4. Magnification


    Dave
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    Re: Questions about Alpa Ground Glass Use

    I use a mask on my ground glass. Phase made one for the p25+. I just taped it on. You could make your own with a clear acetate sheet. I am not sure you want to mark shifts as you simply want to know what is framed.

    I would keep the glass clean, but just to keep the interior of the camera clean. If it does not fit in a one gallon zip lock, how about a camping stuff sack with a draw string. I use those for my equipment to keep dust off. It is also handy when the camera is mounted to a tripod and dust or rain starts to fly in gusty situations as I can cover the camera without taking it off the tripod.

    I would look for a hood for composition. I have only found loupes for focusing. I recommend a loupe with a black spacer to shade from ambient light. Film loupes which can be large for medium-format film usually have a clear spacer. But you could try a 6x6 film loupe. The difficultly with GG is that the angle you view it at is important and so seeing the entire image from a single loupe position may be difficult--edges will appear dark.

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    Re: Questions about Alpa Ground Glass Use

    ALPA have ground glass masks on their website, that can be printed on clear plastic: ALPA of Switzerland - Manufacturers of remarkable cameras - ALPA Ground Glass Stitching Masks You cut to size and fit to the GG.

    I made some a couple of years ago, using an ordinary laser printer, and sheets similar to these: Apollo Laser Printer Transparency Film, 50 Sheets

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    Senior Member darr's Avatar
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    Re: Questions about Alpa Ground Glass Use

    Quote Originally Posted by dchew View Post
    Although I've used a ground glass before on occasion, this is the first time I've owned one so I don't really have a routine developed. Some questions:

    How well do I need to protect it from dust and the elements? I would like to leave it mounted on the STC when in the backpack, but I don't have a way to cover the whole camera. Do I need to put it in a zip lock bag, or is that not necessary?

    The Alpa PGS comes with a 4mm grid but no other marks. I want to add corner marks for 54x40 and some shifted formats. I would rather mark the screen vs using masks so I can see what is around the image. Do I just get a fine point Sharpie and mark away? I'd rather not screw this up; I only have one chance!

    Loupes: I need some help with recommendations. I won't be using this for focusing, only framing, so coverage is more important than magnification. It would be nice to cover the 18mm shift each way, but that would be a huge loupe. So in order of importance:
    1. Coverage
    2. Size (taking this backpacking)
    3. Image quality
    4. Magnification


    Dave
    Hi Dave,

    I actually enjoy composing and focusing on the ground glass so when I made my initial ALPA purchase, I bought the ground glass and leather bellows loupe. I stow the ground glass in a LEE Filter pouch and find it fits well. It is important to keep it clean and away from the elements. I made a contraption from ALPA and Hasselblad parts that works as a quick compositional tool (QCT). It includes an ALPA Hasselblad V back adapter, a Hasselblad Focusing Screen Adapter SWC that has the Acute-Matte D focusing screen with grid (very bright), and various Hasselblad viewfinders depending if I need an upright view or an inline. The QCT's bottom fits the older ALPA cover which makes it easy to stow. Your ground glass should accept one of these covers on the reverse side from the mask holders, but it will not fit inside a LEE pouch if attached.

    I have found no easy way to handle the ground glass other than I wear a fanny pack that holds the ground glass in the pouch and I reach in and out of the pouch during the shoot. If I am out in the landscape, I handhold my MAX with the QCT attached and scope out where I want to anchor myself with what lens as I am able to quickly see through the lens with the QCT. As far as loupes go, I enjoy using the ALPA leather bellows loupe. I find it easy to stow and it does not take up much space, plus it is a decent loupe that blocks out all the light. I do my focusing with it most of the time, but I can also get accurate focus with the QCT. As far as stitching goes I cannot be much help as I do not shoot a lot of landscapes with the ALPA much these days; the more I shoot my Sigma DP Merrill's (really!), the less I want to take the ALPA gear out of the studio.

    Hope this helps some what.
    ~ Darr

    "Creativity takes courage." ~ Henri Matisse
    Darlene Almeda, photoscapes.com
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    Re: Questions about Alpa Ground Glass Use

    I have also used the Hasselblad SWC adapter with some success. Its only real drawback is that it doesn't have diopter adjustments. In the end I have found LV to be the best choice for me. I have also purchased the newer 3400ma batteries which really do provide a noticeable increase in charge life. As for loupes I have found the Peak 4X 2X2 loupe to be extremely clear and very small.

    Victor

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    Senior Member dchew's Avatar
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    Re: Questions about Alpa Ground Glass Use

    Thanks folks, Steve had a good point about the printable masks. I forgot all about those, and it made me realize I can make my own with InDesign.

    Also, I've been thinking about the Rollei viewfinder, but the Hasselblad makes a lot of sense. Just need to find a used Alpa V adapter somewhere.

    BTW, also got the 90 hr with this order. Wow, just wow. And I don't think my other lenses are slouches by any means. But the 90 has that Leica-esque micro contrast wide open all the way out to the frame edges. Yes, feeding Dante's flames...

    Darr, the Lee pouch is a good idea, but I really want to leave the GG on the camera when packed. I may just end up with a zip lock.

    Dave
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    davechewphotography.com

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    Re: Questions about Alpa Ground Glass Use

    So can someone exactly describe the process from composition to finish ? A GG wannabie-newbie begs for some crumbs of wisdom..

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    Senior Member dchew's Avatar
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    Re: Questions about Alpa Ground Glass Use

    Quote Originally Posted by satybhat View Post
    So can someone exactly describe the process from composition to finish ? A GG wannabie-newbie begs for some crumbs of wisdom..
    Not sure if I'm the best to answer since I'm just starting to experiment with the GG, but here it goes.

    I want to keep the GG attached to the camera in the backpack, so for me the first step is mounting the camera and lens on the tripod.

    I dial in rough focus just by estimating distance and setting the HPF ring. I have these frame lines I plan to print onto a clear mask (minus the blue diagonals of course):



    The three formats are:
    1. std 54x40
    2. 72x54 - 2 image vertical stitch to 4:3 ratio
    3. 90 x 40 - Max Pano stitch on my STC.


    Compose as desired then use the D5 Disto to accurately measure distance and set the HPF ring. If there is shift or tilt required, dial that in now with whatever method you like (I use Jae Moon's Numbers spreadsheet for tilt calcs).

    If the final focus setting is much different than the original estimate, recheck framing.

    Remove the GG and mount the back. Estimate exposure and shoot. Shift and shoot for pano's if required, along with LCC's.

    My whole reason for the GG is because as I stitch more, I'm taking an awful lot of shots for each set up (I don't carry a viewfinder or light meter). I've become pretty good at estimating exposure, and focus is spot on with the D5/HPF combo. The only reason for the multiple shots is framing. Without a GG I have no way of accurately seeing the edges without simply taking shots. Sure I can just delete them later, but I'm not a fan of deleting in-camera, so it still becomes a hassle. Who knows, maybe I will find the GG is more of a pain and go back to what I've been doing; I will let you know!

    Since I'm using this only for framing, I just need to see the image. I don't need a 10 - 12x loupe and very dark conditions.

    Dave
    Last edited by dchew; 13th July 2014 at 04:49.
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    Re: Questions about Alpa Ground Glass Use

    Dave,

    I wanted to ask how the ground glass is working out for you now? Do you find it is too much trouble to take on and off in the field, or is it worth it to see you panoramic frame lines before you shoot?
    What did you use to outline the 3 frames ? I have the same setup as you have.
    Thanks,

    John

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    Senior Member dchew's Avatar
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    Re: Questions about Alpa Ground Glass Use

    Quote Originally Posted by Smoothjazz View Post
    Dave,

    I wanted to ask how the ground glass is working out for you now? Do you find it is too much trouble to take on and off in the field, or is it worth it to see you panoramic frame lines before you shoot?
    What did you use to outline the 3 frames ? I have the same setup as you have.
    Thanks,

    John
    Wow I totally forgot about this thread! I do like using the GG. But my use today is a bit different than what I posted before. I tried the clear mask and it didn't really work too well for me. Because it is pretty dark it is hard for me to really see what is a frame line and what is part of the image. Also making the clear sheet with mask lines was no simple task. I couldn't print it on my Epson 7900 with the old clear projector sheets I had. I had to print them out on a laser printer at work, and the damn printer software kept resizing the file. I remember being quite frustrated. I think I did it in indesign or photoshop. I can look and send you the file if you like.

    So I got three Alpa masks: one I left 54x40 and the other two I cut out to make one 54x76 and the other 90x40. So I have one native mask (no shift), one for vertical shift (40 +2*18 = 54x76) and one for horizontal shift (54 + 2*18 = 40x90). Note that Alpa actually has a 6x8 mask which is 56x76. I could have used that if I was smart; probably close enough to 54x76.

    The way I think of it is that as long as I shift max left and right, I can always crop later if I want. I get away with this since a "full frame" sensor covers the camera's entire 18mm shift range with two shots; one left, one right. So as long as I see what I want to see with the mask on, I'm good.

    I leave the GG mounted on the back of the STC in the backpack, which presumably helps with dust since I keep a cap on the front of the camera too. Then I frame using whatever mask is appropriate. I use the Alpa leather bellows / loupe - keeps the light out and I can see the whole image pretty well. Once I have it framed, I usually rough focus using the loupe. If the focus point is pretty obvious I will mount the back and shoot. Or I will pull out the Disto and focus at a precise point if necessary.

    I do not like having to swap out the masks. That can be fumbly with gloves on or in the rain. Now that I think about it I don't think I had the Alpa bellows when I was trying that clear sheet; I was trying to use a Hoodman loupe that didn't cover the whole GG. It might be worth trying the clear sheet combined with the bellows...

    Dave

    Edit: I just looked and used InDesign. I have that file and an output PDF.
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    Re: Questions about Alpa Ground Glass Use

    Thanks Dave.
    I have the 6x7 mask, so I will start with that, as you recommend. If you are shooting a 2-shot vertical, and I shift all the way right 16mm for the first shot, then all the way left 16mm for the second shot, I calculate (with my 40x54 sensor) that there will be a 4mm overlap for each shot.
    Is this adequate to merge the two shots together reliably?

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    Re: Questions about Alpa Ground Glass Use

    Hmm. I think your math is short changing your sensor

    If you shift 16 mm I'm pretty sure that gives you an 8mm overlap. If you could shift 20 mm, that would be zero. 19 mm would be 1mm overlap, but on each side for a total of 2mm. The other way to look at it is a 16mm shift gives you 16x2+40=72mm. Zero overlap would be an image size of 80mm, so you are overlapping 80-72=8mm

    Regardless, I have found shifting 18 mm (with I think a total of 4mm overlap) not to be a problem. If you like I can post a few images this weekend or send you full files for you to look at, but am not home right now.

    Ciao,
    Dave

    Edit: or maybe my definition of overlap is different than everyone else's!
    Last edited by dchew; 24th July 2015 at 13:58.
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    Re: Questions about Alpa Ground Glass Use

    To be sure I wasn't crazy (well, at least about this topic), here is a better description. This is supposed to show a two image horizontal shift with the sensor mounted in portrait. Image 1 is the first of the series, image 2 the second. I put one above the other to make it easy to see, but note they are really in the same vertical position; these are shifted left and right not up and down.

    The red line is the original centerline of the sensor; the black outline shows the final image size. The first example is the dumb one - no shift so both images are the same. I did that to show that the math works both at zero shift and at 20mm. I did the third example because it is easy to see. The sensor is shifted 1/4 of its size (10mm) but the total overlap is clearly 1/2 of the sensor area. The last 2 are Smoothjazz's 16mm and my 18mm shifts.





    I think the reason why I don't see any issues with such little overlap is because shifting via the back makes the stitching software's job easy since the perspective is exactly the same (I just use PS - now LR). Here are two examples. They've been cropped a bit for framing/artistic reasons, but they were shifted 18mm each way.

    Dave



    Last edited by dchew; 25th July 2015 at 04:32.
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    Re: Questions about Alpa Ground Glass Use

    I do a lot of shifting with my Credo 50 and also with my IQ180..... never beyond 10mm. With my back in landscape a 10mm shift left and right will equal an almost perfect 2X1 which I usually crop to 16X9. In Portrait a 10mm shift left and right will equal a 4X3 and my Credo 50 turns into an IQ180 resolution wise.

    Victor
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    Re: Questions about Alpa Ground Glass Use

    Dave I love your pictures, and love this perspective!
    The pictures are helpful- thank you. I actually drew out the same frames to clarify it too.
    The only one point I had about the 18mm shift is that technically, around the center line of the frame, you have 2mm of overlap for each shot. You are right, it is 4mm total, but each image overlaps the center by 2mm.
    (40mm shifted 18mm leaves 22mm in the original frame). I thought that it might be cutting it close, but it looks like there is no problem at all.

    I have the Alpa Stc; at 16mm there is a slight click or detente, then it goes out to 18mm. Does yours do this too?
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    Re: Questions about Alpa Ground Glass Use

    Quote Originally Posted by Smoothjazz View Post

    I have the Alpa Stc; at 16mm there is a slight click or detente, then it goes out to 18mm. Does yours do this too?
    Although directed at Dave I'll volunteer that my STC does not have any slight click or detente at 16mm. The only detente I have is at '0'.

    Victor

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    Re: Questions about Alpa Ground Glass Use

    Thanks! Yeah I agree on the 2 vs 4 mm; it just depends on how you look at it.

    I've been looking at a bunch of horizontal portrait stitches in my images. I did find one that has a problem. I don't know if you would see it in even a big print. The photo is from a glacier on Mount Blanc, and if you zoom into the cables going up the Aiguille du Midi, there is a spot where the cables are not contiguous. I presume that is from the stitching process. The cables are pretty darn faint though. I might not get away with the 4mm of overlap on architecture.

    In regards to the STC, like Victor I do not have any detent at 16mm only 0. Mine is a 2010 vintage, so maybe they added that after. Note that I would not stitch 18mm with a wide angle. Most of my stitching is with either the 60xl, 90hrsw or sk150. Those lenses can comfortably go wider than my camera can move.

    Dave
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    Re: Questions about Alpa Ground Glass Use

    Thanks Dave. By the way, what software do you use to stitch your images together? Right now I am looking at the Photoshop photomerge program, and also PTgui.
    Thanks,
    John

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    Re: Questions about Alpa Ground Glass Use

    John,
    I just use Photoshop for these stitches where the back is shifted. It seems to do just fine. I have PTgui for other more complicated stitches, or when sticking with my a7r.

    Dave
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