8x10 Macro Camera

Introduction: 8x10 Macro Camera

About: Photography teacher, woodworker, and general repair man

I started this project long ago. Originally, it was to photograph hummingbirds in flight at a 2:1 reproduction ration on 8x10 film. However, life got in the way and I never managed to take the photos.

Fast forward six years and now I’m teaching Commercial Photography. Most kids will never need to know about bellows extension formulae, extension tubes, or how to build their own camera out of antique equipment. That doesn’t mean that we shouldn’t cover it. So, I modified my original camera so now it shoots 4:1 macro shots and I was able to teach my kids all about extension factors.

Just an FYI, I lost my original build photos in a flood that damaged my computer so I had to draw everything.

(this guide is licensed under Attribution and non-commercial however, the images created by the camera are not. Please contact me for image use)

Supplies

Camera:

1 - 48x120" 1/2" sheet of plywood

1 - 2x6x120" - wood

1 - 2x14x14 - wood

1 - 14x14x1/2 or 3/4" plywood

black paint

5 - tubes of black silicone

1 box - 1 1/4" drywall screws

1 box - 2" wood screws

1 package - 1/2" conduit fasteners (really just need four or so)

Photography:

1 - large format lens that's long (over 300mm)

1 - 8x10 ground glass back.

1 - 8x10 film holder

1 - Changing bag

1 - pack of 8x10 sheet film. I used Portra 160 or Tmax 100

1 - light meter

2 - Powerlight 2500

1 - wireless triggering set

1 - some sort of strong tripod with a geared column

1 - 3-axis rotary milling table

optional:

Nikon 210mm Copal 1 shutter

cable release

PC cord

Tools:

Cordless drill or driver

table saw

router or jigsaw

Step 1: Choose a Lens

Like I said, originally, I wanted to photograph hummingbirds

in flight. Therefore, I needed a long lens to give me adequate space between the front element and where the hummingbird would be feeding. So, I opted for a 610mm Bausch and Lomb Aero Tessar. These lenses can be had for cheap, like $70 on ebay. They were originally used to photograph bombing runs and perform reconnaissance in World War II. It’s kind of fun knowing that a lens that was used to photograph the obliteration of a continent is now being used to photograph flowers, shells, and bubbles as well as teaching kids.

The longer your lens, the farther you can have your object from the camera lens and still be in focus. If you use a short lens, you will need to have the item closer to the lens (the equations to figure distance are below). Also, the longer your lens, the longer your camera will have to be to achieve your desired magnification ratio, so keep that in mind.

Like I said, I don't have any before photos but here is one on Pinterest: https://www.pinterest.com/pin/289637819765165009/

It's big, it's ugly, it was cheap and came with a housing to turn it into a telescope.

Step 2: Math! Part 1

To design your camera, you need to know your focal length

and reproduction ratio.

First off, every lens has a specific point where it will focus when your object is “infinity” away. This is called the Focal Length. For my 610mm lens, it will focus an image 610mm away from optical center of the lens (not the rear element). A 50mm lens will focus an image 50mm away from the optical center of the lens at infinity (unless there are other focusing aspects to the lens). You will need to know the focal length of your lens for the rest of these calculations.

For me, I know that I wanted a 4:1 reproduction ratio. I knew that because I’ve worked with photography for a lifetime. If you don’t know what you want, you can figure it out by knowing how large you want a 1 inch object to be on your film or knowing how large of an object you want to fill your frame. I went with the later approach. I wanted a 2-inch object to fill the frame.

So:

8-inch short side of the frame / 2 inches = 4:1 reproduction ratio.

Now, to design your camera, you need to multiply your reproduction ratio by your focal length (this is called your bellows extension) and then add your focal length back in.

So, our equation becomes:

(Focal length x Reproduction factor) + Focal Length = Total focal length

4 x 610mm + 610mm = 3050mm of total camera

You need to add in your original focal length because the lens is originally designed to focus an image at 610mm from the lens. In order to get the macro reproduction ratio, we want to extend the film plane back behind the original film plane.

(technically, the center of the optical system to the focusing plane needs to be 3050mm. However, I’m building this camera out of plywood, a $70 antique lens, and dimensional lumber. It will be close enough to round to a 4:1 reproduction ratio if I assume that my total camera length needs to be 3050mm)

Side note: this is also how old cameras with the bellows worked for focusing. However, instead of moving the film plane, the lens moved along a track. Moving the lens out, away from the focusing plane, will allow you to focus on things that are closer. After moving the lens away from the film plane far enough, you end up focusing at 1:1 or greater reproduction ratios, which is considered macro. Newer lenses work in similar fashion by moving elements inside the lens forward and backward but have additional elements which work to standardize the distance to the focal plane (so a modern DSLR 200mm and 17mm lens focus at the sensor).

Step 3: Build Your Camera

Like I said, I lost my original photos. Please excuse my drawings.

There are really just three key elements to a camera. It has a light tight box, something to project the image on to (and record), and a lens or hole to let light in.

First off, you need to remember that this was originally going to be a 2:1 macro camera. I’ve transformed it into a 4:1 camera. That meant that I had to cut my original box in half and extend it. I’m going to leave that part out and assume that we’re starting over.

We’re going to start with the sides of the box. This is so that you can shim and align your lens and film plane later. For me, since I knew the entire camera needed to be 3050mm, I converted everything to inches because it’s what my tape measurers are in. 3050mm equals 120 inches (3050mm/25.4mm = 120 inches).Then, I subtracted 1.5” from the total length because I know that’s what my lens board would be made from. That gave me 118.5” box length. You can choose to trim the end of your plywood or just leave it at 120”, the extra 1.5 inches won’t make much of a difference in the end (just update your math accordingly, your new bellows extension will be 2440mm+37mm = 2477mm).

The interior of the box needs to be larger than your film. I’m using 8x10 sheet film so the rear of my camera needs to be at least 8x10” on the interior. However, since I need to account for film holders, focusing screens, and to make my life easier, I went for 10x13” on my interior dimensions to give me some wiggle room and keep things simple. Those dimensions allowed me to use just one sheet of plywood. So, if you’re using 1/2” plywood and can find 10’ sheets of plywood then you can cut your boards into two 10”x118.5” and two 14”x118.5” pieces.

Paint the interior sides of your wood with flat black paint. Spray paint is flatter than latex but I used the darkest black latex that I could get. All you’re trying to do is keep reflections on the inside of the camera to a minimum. If you don’t paint the inside of the camera, you may introduce reflections which can fog your film from the extra diffused light bouncing around inside the system.

Form your box by keeping your short sides on the inside of your long sides. When you’re gluing the box together, be sure to put black silicone caulk in the joints before screwing it together, this will prevent light leaks.

Then, build your reinforcements at the ends. These are simply 2x6” boards that wrap around the outside of the box. For each end, you will need four 14” pieces. Start by laying your first piece on one of the long, 14” sides, align it with the plywood, and screw it down. Then, turn the box 90-degrees and line up the ends of your 2x6s. Screw that down. Repeat this process until everything is in place on both ends. Your box ends should be banded with 2x6s now.

Next, we need to build whatever is going to hold your film holders and align the film plane to your lens. I changed my original design when I got my hands on the ground glass back. Both designs started with a ½-3/4” piece of plywood cut to 14x14” with an 8x10” hole cut directly out of the middle. If you’re using a ground glass focusing back from an actual camera, you will need to make all the necessary adjustments to your piece of wood now (I routed an 11.2x11.2” channel around my hole so that the back would sit firmly down in the plywood since it was designed that way for the actual camera). After this step, you cannot get the back off the camera without damaging the camera.

Film Plane Alignment:

Before affixing your back to your camera, stand the camera up on its end. Then, level the camera. You could use a bubble level or digital level for this but be warned, you could be up to 0.1-degree off. At 10’ and a 4x magnification, that is enough to cause focusing issues. So, to get around that, you need to get the longest, most straight 2x4 you can, then place it across the “top” of the camera. Now, measure the height of each end of the 2x4 and shim the camera as needed to get it perfectly aligned. Once aligned, slather the 2x6 mounting faces with black silicone and place your plywood back on top. Lightly screw the plywood back into place but not fully down. Use the same 2x4 alignment technique to level your film plane and screw it into place so that the silicone gushed out the sides (smooth that out).

Take a break and let everything dry. Or, move on to the lens board.

Lens Board:

This is tough to write for because every lens is different and shaped differently. My lens is really heavy, so I mounted it in a 2x14. Simply find the diameter of your lens at the point where you will be mounting it, cut a hole that large in the center of the board, and then put your lens in that hole. To align it, I just put it on a flat surface, front side down, placed ½” wood scraps on the table, and then slid the board over the back of the lens until it was also flat on the wood scraps. Then, I siliconed it into place. If your lens isn’t firmly in place, use pipe straps to hold it down. It isn’t ideal but it gave me something close to work with. The ½” scraps are there to keep the front of your lens up off the board. That way, when you go to align the lens to the film plane, you’re aligning the lens and not the board.

If your box and back are dry, invert it so the “front” of the camera is upright. DO NOT ALIGN THE SIDES. At this point, we are only going to align the lens. Use the same method as what you did for aligning the back (squirt silicone on the 2x6 mating surfaces, lightly place your lens board on top, align with long 2x4, secure, let dry).

(There is a picture where you can see the pipe strapping on the back of the lens board)

Assemble the film holder mechanism:

Again, I was lucky enough to fall into a teaching position that had an old 8x10 view camera laying around so I borrowed the back. I secured it with conduit holders, it was really simple.

Seal up any light leaks

Go around your camera and seal up any light leaks that may be present. Just put a small bead of silicone on each seam and joint and then smooth it out. Pay close attention to the joint around the lens and the lens board.

Step 4: Math! Part 2: Exposure Compensation

Knowing your reproduction ratio, you can consult the internet to discover your depth of field at specific aperture f-stops. This depth of field will change depending on your reproduction ratio and aperture size. Using this table, you can decide how deep you need your depth of field to be and then the next set of equations will be a bit more useful. For me, I’ll be shooting at f/32 so that I can have 1mm of perfectly in focus image.

(I used the table about midway down on this page and he also includes the formula to do the math yourself if you feel like it http://www.bobatkins.com/photography/technical/depth_of_field.html)

Light loss:

Light follows the inverse square law. So, if you double the distance from the light source to the lens, you end up with 1/4th the density of light hitting the sensor/film all else being equal. To find the specific loss of light intensity, in stops, follow the following formula:

((Bellows extension/Focal length)^2)log 2 = stops of compensation (remember, bellows extension is just reproduction ratio x focal length so ours is 2440mm)

For my case, the formula becomes:

((2440mm/610mm)^2)log2

((4)^2)log2

16 x log2

4.8 stops

Or, a simple way to estimate the compensation is:

Reproduction factor + 1 = stops of compensation

For us, it becomes 4 + 1 = 5 stops of compensation

Under less than ¼ stop over exposure won’t hurt anything and makes my math a whole lot easier, so I’m going with that. Add the five stops of compensation to your actual aperture value to get your equivalent aperture. In this case, my equivalent is going to be f/128 + 1 stop (f/181 but meters don’t go that high).

Next, we need to approximate where our object to be photographed needs to be. To figure that out, we use the following formula:

1/focal length = 1/bellows extension + 1/focusing distance

Let’s get focusing distance on its on with some simple algebra:

1/focal length - 1/bellows extension = 1/focusing distance

1/610mm – 1/2440mm = 1/focusing distance

0.0016393 – 0.0004098 = 1/focusing distance

0.0011896 = 1/focusing distance

Focusing distance = 1/0.0011896

Focusing distance = 813mm from the center of the optical system (roughly the aperture)

Step 5: Photography

It will take roughly 1000w of constant light to be able to barely see the image projected onto the ground glass. I measured roughly 800mm from the front of my lens and plopped a focusing target down. Then, I did more major adjustments by pushing the target forward and back by about 5mm at a time. Having a second person to move the target while you look through the glass is incredibly helpful.

Once you are close to having perfect focus, switch over to the milling station for fine focus. Set your target up on the milling station and slowly move forward and backward by about 1mm at a time until you can see the dots on your paper left by your printer.

The milling station is perfect for this because you can’t make fast focus adjustments. It can also rotate to reposition your object and slide right to left (in addition to the forward and backward “focusing” motion) to position your object on the x-axis. I also used an old, broken, large format tripod that has a geared column so that I could also control the y-axis.

For flashes, I used a pair of Powerlight 2500s with digital readouts. The digital readout is super handy because it will tell you how many watt/seconds which allows you to easily do math to calculate your exposure. I got my lights as close to my objects as I could and then fired them through a piece of white plexi glass to act as a difuser.

After taking a lot of light meter readings, I found that at 62 w/s, I should set my aperture at f/32. So, adjusting for my light loss, I need to have 2000 w/s per exposure.

62 w/s = f/32

125 w/s = f/45

250 w/s = f/65

500 w/s = f/90

1000 w/s = f/125

2000 w/s = f/125 + 1 (f/181)

Remember, if you need brighter light but don’t have the flashes, you may be able to just move your current lights closer to your object. Just like how you lose light intensity as you move away from your light, you gain intensity as you get closer. If you can cut the distance to your object in half, you will gain two stops of intensity!

To shoot the photo, you don’t really need to worry about ambient light. The settings for my room were 1/15 second @ f/4 @ ISO 800. That’s 12 stops difference between ambient and proper exposure. In other words, it woud take 5 minutes of ambient exposure to properly expose the film (more because of the reciprocity of failure of the film). With that in mind, after everything was focused, I shut off my modeling/focusing lamps, pulled the dark slide on my film holder, fired the flashes manually with a pocket wizard, and put the dark slide back in.

Step 6: Optional Shutter

Since I was going to use this camera to photograph hummingbirds outside, I originally needed a working shutter and flash sync port. For that, I took an old Copal 1 shutter out of a 210mm lens and used the aperture blades on the 610mm to hold it in place because the 610mm didn’t have a shutter or port. I was able to feed the release and PC cable through an old port which was used for the no-longer existent wiring in the lens.

The only issue is that in order to cock the shutter, I have to remove the front element of the lens. Because of this, I just left the shutter open and fired the flashes manually for this project.

The math to account for the shutter instead of using the built-in aperture is pretty simple. We know that the math to figure f-stops is:

Focal length/aperture diameter = f-stop number

So with a goal of f/32, we know that:

610/a = 32

610/32 = a

19mm = a

I can either measure the 210mm shutter hole or use the aperture scale already built into the lens. I opted for the aperture scale because I left my micrometer at home. So, using the same formula with a bit different numbers, we get:

210/19 (target aperture) = 11

F/11 on my shutter is equivalent to f/32 on my 610mm lens.

Be the First to Share

    Recommendations

    • Reclaimed Materials Contest

      Reclaimed Materials Contest
    • Edible Art Challenge

      Edible Art Challenge
    • Tiny Things Speed Challenge

      Tiny Things Speed Challenge

    Comments