Flange Focal Distance Part II

So apparently my theory on Flange Focal Distance being a factor in my focusing problems seemed to be a dud. It turns out that I can hold the camera actually a fair distance away from the flange mount without any observable degradation in image quality.
In hindsight this makes some kind of sense. As the microscope acts as the camera’s lens, the light hitting the sensor must be relatively parallel.

To test this I actually decoupled the camera from it’s mount and shot lens-less from a ways back in a darkened room.

So going from fully attached to several dozen millimeters out changed my image impressively little.


Microscope Focal Distance 2


Microscope Focal Distance 1

Hand Held










Microscope Focal Distance 4

Hand Held

Microscope Focal Distance 3





Flange Focal Distance

I am not a professor of optics.

That being said I do understand that there’s a lot to learn about hooking a camera up to a microscope and I am woefully ignorant of the minutia.

But this is science and it is full of venturing into the unknown, even if many have already figured it out.

So one of the problems I have been having with the Versamet microscope is that everything on the camera was out of focus compared to the eyepiece. I did a little correction with the fine adjustment focus knob to get around the issue. But being limited to a Canon 5D without live view meant I had to focus everything through the eyepiece. Cumbersome and uncomfortable are appropriate words here. This meant that the photo quality suffered.

Then I discovered Flange Focal Distance. It was something I was vaguely aware of but didn’t know it was critical. When light exits the rear of a lens heading for the image sensor (or film), the light rays aren’t actually parallel. Thus placing the sensor closer to or further away from the lens flange than designed can lead to a fuzzy shot.

From Wikipedia

From Wikipedia

Now it seems that the Leica M mount that originally came with the microscope had a focal distance of 27.8 mm while the Canon EF mount tops in at 44.0 mm. There’s enough of a disparity there to make me think that this may be a factor in my images.

Solving this issue should bring my eyepiece focus and camera focus to the same point. Hopefully it will also help my falloff problem and light up the edges of my pictures. Unfortunately with my microscope out on loan I can’t do anything about this at the moment. I’ll provide an update when I get a chance to tackle this problem.

Repairing a Canon 5D

The Canon 5D is a beautiful Digital SLR camera that retailed for far more than I’m willing to spend on a camera when it was introduced back in 2005. Fortunately with newer generations of the 5D coming out, it’s price has dropped to something more reasonable, even cheaper if it doesn’t work.
I bought a Canon 5D about 2 months ago with the interest of outgrowing my little powershot. I knew it had problems, but I thought that I would be able to fix them. For the price and the included accessories, I didn’t think I was losing out on the deal even if it was irreparable.
I tore into the camera and found nothing out of the ordinary. I spent 2 days with it in pieces on my desk and couldn’t figure it out. To the camera’s credit, it’s really well engineered and is made to be serviced.
I decided to purchase a second used camera to see if I could trace out the problem. I should be able to sell the spare camera once I’m done and make back a reasonable amount.
Which brings us to today.

The problem with Camera #1 (on the left) is that aside from the top LCD, it’s completely unresponsive. I sat the cameras side by side and checked the differences in the top LCD.

The idea here is that Camera #2 is a “known good”. Everything seems to be functioning as it should. By swapping parts between the two cameras, I can narrow down the problem. Rather than tearing down #2 and inserting known good parts, I will be inserting the unknown parts into camera #2 to confirm function. If suddenly both cameras cease to work, then I know that I’ve both found a bad part and that #1 has multiple failures.

The first thing to do once the rear covers are off is to swap them to check the rear LCD.Backs off
Camera #2 lights up. Both LCDs are good.

What about swapping the secondary board? I thought it might be the processor board, but that requires desoldering parts to pull it out.

A swap and camera #1 is still dead. #2 responds fine.

Darn. That’s all I can do without firing up my soldering iron. I have to carefully remove the shields on the center of the processor boards. Unfortunately, the solder that Canon uses seems to melt at a higher temp than what I normally use and it takes a little time, but I manage. I’m pretty sure that it’s the processor board. Apparently that’s known for failing and I can order new ones on ebay.

At this point, Camera #1 contains known good Rear LCD, Secondary board and primary processor board and still doesn’t light up. Camera #2 functions.
Well… Shit.

The next switch comes without much hope, but I have to take off the top of the camera to access the power board so I check the top LCD and don’t see a change.

About what I expected.Power Board Closeup
The power board has 2 soldered terminals leading directly to the battery. Since my iron was still hot, this didn’t take much time. However, I did have to spend a while with some solder wick to clean the thru holes for the terminals. Swap the boards, resolder the connections, flip the switch and…

Nothing changes.

Wow. That’s almost everything I can think of. The good news was that all of the boards that I thought could be fried are actually working. The bad news is that I still don’t know where the problem is and I have to go deeper.

I wonder if I can isolate some parts by just leaving some of those ribbon cables unplugged. As I have a “known good” camera, I can start unplugging things and see what happens.

If I remove the red and black power wires from the top of the power board, camera #2 shuts off and stops working. Replace that.

Unplugging the upper 3 ribbon cables on the power board causes 3 shutter clicks on power up. Interesting.
Camera #1? 3 clicks! This is the first sign of life I’ve seen out of this outside of the upper LCD.Now I know that it’s not a jammed shutter.

There’s one more large board in there that I haven’t gotten to yet. The DC/DC converter board. This one requires some desoldering and some finicky tight cables to get out. Of the 4 soldered wires, 2 of them go to the video out port (It’s a dual function board). Since it’s an open circuit anyway, I’ll leave them disconnected for the switch.

Another swap, some soldering and crossing my fingers.

Camera #1 is working! The rear LCD is on and the top LCD shows the shots left on the CF card. Can I hope that everything works?
A press of the shutter gives a very satisfying *clickit*.

So now I’ve found the problem. The DC/DC converter board is bad. Ebay shows replacements selling for about $80. Not bad. Not great, but doable.

Let’s see what burnt out. A little finessing with my soldering iron and the shield comes off.

I don’t see anything. I did absent mindedly flick off a little piece of loose solder from one of the traces, but nothing appears burnt or otherwise shorted. I do notice a few SMD fuses on the back and pull out my multimeter to find that F103 is open. It has a little “P” on it, but I don’t know what that means.

The fuse looks like a 0603 SMD fuse. 0603 is a standard surface mount size that I use for my own boards. It’s about the lower limit of sanity for DIY. A quick check with my calipers confirms the size, but the height is really thin.

I don’t have much experience with SMD fuses so I have no idea what the “P” stands for. Google turns up this forum (http://forum.thinkpads.com/viewtopic.php?f=46&t=85680) on ThinkPads where someone  traces a backlight problem to a “P” type fuse that looks exactly like mine. They suggest a Digikey part  LittleFuse part # 0467003.NR which leads me to the Datasheet. A “P” on the fuse means that it’s rated for 3 Amps.

Digikey is my go-to source for looking up electronics so I start looking for alternatives. It seems that the majority of 0603 fuses are much taller than mine and indeed the “Littelfuse Inc” part seems to be the best match. Now we’re talking $.94 for a replacement.

Let’s see if the fuse is the only problem before we get to ordering the part.

I carefully solder some small wires to either end of F103. Any larger wires would make me nervous about tearing off a solder pad from the board. On the other end of the wires I solder in a large 3 amp automotive style fuse.

F103 check

Soldering another fuse in parallel to Fuse 103.


Automotice Fuse Soldered in Place








Plug the board back in and it works! I’ve confirmed that the fuse is bad. Now to make a digikey order.