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Canon Ef 12 Extension Tube

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Canon Extension Tube Ef 25 Ii User Manual Instructions

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Changing focus screen
Modifying Canon EF Extension tube for EF-S Lens

One problem with autofocus cameras is that they are designed on theassumption that AF is always good enough, so little attention is given to making manualfocussing easier - this is a particular problem in low light. Older non-AF camerasincorporated various clever optical tricks in their focus screens to make focussingeasier, and it is possible to transplant these into the EOS 300D/Rebel to help manualfocussing.
I used a Canon E-A screen, designed for the EOS 620/650, which has interchangeablescreens, but any plastic screen of similar thickness ought to be adaptable.

Take great care to avoid touching the surface of the screen, asthe fine surface will be very easily damaged or contaminated. Handle ONLY by the edges.

The screen needs to be cut down to 29 x 17mm to suit the smaller framesize of the EOS300D. To help with this, I've produced thistemplate (PDF 7K), which you can print and lay the old screen out on to cut it. Checkthet the inner frame is 29x17mm in case of promter scaling errors.
You don't need to replicate the tabs on the original screen - it just needs cutting to thesmaller size.

The method I used was as follows :
Carefully place the screen, shiny side up on the template, taking care to get it centredand square. Tape it down, avoiding getting the adhesive tape on the area to be retained.Using a ruler and sharp knife, score along the cut lines. Remove the tape, turn it overand score the lines on the other side, taking care to look straight down on the line toavoid parallax error. This pic shows the screen after scoring :

Using pliers, carefully snap off the edges - they may come off in one or two pieces. Ifnecessary, smooth off the edges by placing some fine (400+ grit) abrasive paper on a flatsurface, and rub the edge of the screen on the paper, taking care to hold it square.Thoroughly trim any swarf and clean off dust with an air duster.

Fitting is fairly straightforward:
Remove the lens and rest the camera upside-down, i.e. sitting on the flash shoe, so thefocus screen is horizontal. It is adviseable to place something like a tissue or clothover the mirror to avoid marking it accidentally.

Using fine tweezers or a small pointed implement, insert the point in the small hole inthe tab (circled below) of the screen retaining clip (you may need to push back the softblack foam to see it), and push the tab back towards the rear of the camera - when pushedapprox. 2mm back, the clip will release and spring upwards.

Remove the clip with tweezers. Place something soft over the mirror, and tilt the bodybackwards to lie on its back, and the screen (and possibly a copper coloured frame) willdrop out onto the mirror. Remove the screen with tweezers (hold by the EDGE ONLY to avoidscratching), return the camera to the former 'upside down' position, and replace thecopper frame.

Place the new screen, shiny side outwards, on top of the copper frame, and check thatit is centred and square. (If refitting the original screen, the edge with the single tabgoes towards the rear of the camera.) Tapping the side of the camera is a good way tojiggle it into place.
Replace the retaining clip by holding it with tweezers, insert the 2 tabs on the rear intothe holes, hinge it down until it comes to rest, then press the front tab down with afinger until it clicks, latching the screen in place. If it doesn't click, don't force it- chances are the screen or the copper frame is not sitting properly in place.

One disadvantage with this is you lose the focus marks - in lower light you can see afuzzy red blob, but not very visible in brighter light. I think the marks are implementedwith specially angled areas on the original one and I can't see how you could makesuitable marks on a new screen - I tried making indentations in the new screen, but thisdidn't help at all.

Canon's EOS 300D digital SLR comes with a lens in a new variation of Canon's EF format,EF-S. This has a projection on the rear, which prevents the use of old Canon extensiontubes for close-up work. Canon have redesigned the tubes (new ones have a II designation -e.g. EF25 II), however if you already have one of the old EF tubes, this page describeshow they can be modified to fit the EF-S lens, to save the expense of upgrading. The oldertubes will probably also be available more cheaply second-hand.
I did the mod on the 25mm EF25 tube - I have not seen the EF12 closely, but would imaginethat it could be similarly modified.

Tools required : number 00 Pozi screwdriver, either a Dremel type toolwith cylindrical burr, or a large half-round file.

Remove4 screws (#00 Pozi) in camera mounting ring.

Removecamera mount ring, taking care not to damage wires.
Remove 3 screws holding plastic inner tube

Removeplastic inner tube.

DO NOT be tempted to remove the plastic block that holds the gold contacts, as thecontacts and springs will fall out and they are somewhat fiddly to reassemble!

Turnover. Mark a 40mm dia ring on lens side of this part. The old hole is 35mm, so the easiestway is to use a pair of dividers to scribe a mark 2.5mm outside the original edge.

Onthe camera side, there are 2 mounting posts for a clip which retains the 'lens present'detection switch. These posts are within the 2.5mm area to be removed. There are 2 optionsto deal with this :

1) If using a Dremel tool or similar, it is possible to cut away the required amount ofthe ring without destroying the posts - this requires a lot of care, but should just bepossible, leaving enough of the posts intact for the screws to hold the clip

2)If cutting with a half-round file, this will destroy the posts, and render the switchunuseable. This is no big deal as it just means the camera can't detect whether a lens ispresent or not.
However you need to bypass the switch so the camera thinks the lens is always present -cut the wires to the switch contacts, strip back and twist tightly together. Ideally, theyshould then be soldered and covered in heat-shrink sleeving, but twisting about 5mm lengthtightly and covering with sleeving or adhesive tape will suffice if you can't solder.

The enlarged hole in the ring after cutting.

Take great care not to damage the gold contact pins or the wires. If using a file, youwill end up cutting slightly (about 0.5mm) into the plastic block that holds the contactpins - this is not a problem as long as you don't cut too deeply into it. Chamfering thehole slightly so that it is slightly larger at the lens end will help reduce the amountthat you cut into the contact block.

Test-fit the lens to ensure it fits easily, without distorting the rubber surround onthe lens.

Removeabout 1mm from the end of the inner tube, to provide clearance for the lens.

Canon Eos Extension Tubes

The easiest way to do this is to lay some medium-grit (100-200) wet & dry (siliconcarbide) paper on a hard, flat surface, and rub the tube around on the paper in a circularmotion, taking care to apply pressure evenly. The amount removed is not critical - itneeds to be enough for the lens to fit, but removing a bit more will not hurt.

Canon Extension Tube Ef 25 Ii User Manual Pdf

When you have removed enough, trim off the edges with a sharp knife to remove the swarffrom the rubbing operation.

To check the fit, place the tube in position without the screws, then fit the lens frombelow, and check that moving the lens does not move the tube, i.e. it is not touching theend of the tube.

Thoroughlyremove all dust and swarf (use a compressed air duster if available), then re-fit theinner tube, and then the camera-mount ring, taking care to avoid trapping any wires, andensuring that you mount the ring in the correct position, so the contacts line up on eachside.

This image shows the lens end of the finished result.

Asa finishing touch, you can add a white location mark for the EF-S lens.

Use a sharp 3mm twist-drill held in your fingers (NOT IN A POWER DRILL!!!) to make asmall indentation, then fill with white paint or correction fluid.

The first thing to note is that an extension tube confuses the hell outof the auto-focus system, so you will always need to use manual focussing.Focusand zoom also interact substantially, and depth of field is typically small, so you willoften need to use a small aperture and a tripod to cope with the correspondingly longerexposure times.

Canon Extension Tube Ef 25 Ii User Manual 2016

With the EF25 tube, the standard 18-55mm EF-S lens will focus objectsbetween 0 to 150mm from the lens.

Un-cropped images illustrating size range

Tip of a 0.7mm pencil

One of the screws I had left over... (lens switch clip mount)

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