Upgrading a Nikon D40 viewfinder to split-prism focus screen

Since being given a Nikon F60 SLR some twelve years ago or so, I’ve struggled with the standard viewfinders provided on modern consumer-grade SLR cameras.  My annoyance was further amplified when I bought my factory-reconditioned D40 in 2008.

The problem shared by both these cameras is that the viewfinder is not terribly precise.  It’s easy enough in most lighting situations to see whether the frame is generally in or out of focus, but to do so with any precision is challenging at best.  Quite often I find my eye automatically compensates  for poor focus by focussing on the subject “through” the screen itself.  I do this without even thinking about it, despite whatever conscious effort I make to prevent it happening.

Specific to the D40 is the issue that the viewfinder is about 1.5x smaller than the F60 I had been used to, and certainly smaller than the more professionally-oriented devices Nikon currently offers.  Not only is it smaller, but it’s also dimmer.  Sure, I willingly bought the D40 knowing about these issues, but they’ve become more of a show-stopper as I’ve grown to move away from shiny new auto-focussing lenses to older manually-focussing units.

I did some research into possible solutions that didn’t involve buying a new camera body, and I soon found that like pretty much every other Nikon SLR out there, the focussing screen on the D40 is easily removable – presumably for cleaning.  This also opens the way to replacing the existing screen with something more suited to the way I want to work – that is to use split-prism and/or microprism focussing rather than relying on the built-in autofocus system.

I won’t explain how split-prism focussing works, as it’s done so much better here.


The screen I chose was a generic (no brand name) cheap unit found on eBay, but it’s like this one. Instructions were found online here, which gave me enough information to know what to expect.  Lacking specialist tools, I washed my hands and used my index finger (and nail) to operate the latch that holds the screen in place, and used clean fingers to drop the shim and screen into place.  The wrapping on the new screen was enough to place between the mirror and the latch to prevent scratching.

I’m not always the most practical of people, and yet this installation job was easily done in less than 20mins including making some tea and reading the manuals – and I’ve never done anything like this before!


The concept proved itself very rapidly in ‘everyday’ snapshot situations. But something was wrong: when I manually focussed using the new screen, the image turned out with the actual focal point being shifted a little behind what I’d focussed on.  Pants.

Given that my lenses hadn’t changed, and given the assurance I’ve had from several sources that the choice (or even presence) of screen does not interfere with the camera’s built-in autofocus sensors, there was only one answer: the screen was out of alignment.

Back to Google and Flickr forums I went, and found that this is a common enough issue experienced when installing and using custom screens – particularly cheap ones like mine. Whether this problem reflects the quality of the cheaper screens, or whether it’s caused by the quality of calibration carried out in the manufacture of the camera itself, I cannot tell.

Before going any further, I found and printed a focussing test chart (more on the issues that brought up here!) and took some autofocus-assisted shots of it with the kit lens. First with the new screen, then with the old, and finally even without a screen.  This confirmed what I had read, namely that the autofocus works as it should.  Good – just the manual focussing to sort then.

The research I’d previously carried out into the problem suggested using some special tools to recalibrate the mirror, so it naturally rests in a different place.  In this camera this would inevitably mess up the autofocus system too, which I felt would be too complex a job to realign with the tools and time I had at my disposal.  There had to be a simpler solution!

So I gave the issue some thought, and basically I cheated.  I figured that if moving the mirror in relation to the screen can solve the problem, then why not move the screen in relation to the mirror instead?  If this can be done without putting too much pressure on the screen assembly (and damaging either the screen in the camera in the process) then it has to be worth a shot – right?


I pulled the screen and shim back out of the camera, and first decided to try installing the new screen without the metal shim.  This moved the screen further away from the mirror.  Took some test shots, and soon saw that the back-focus problem had gotten worse.  Okay, then if that was the case then perhaps instead I needed to effectively thicken the shim to move the screen closer to the mirror?

Buying a second shim to test this theory seemed like too much work, not to mention that this would mean throwing yet more time and money at the problem, with no guarantee of a workable solution.  What if the spendy new shim added too much thickness?

So instead I thought to try sticking some appropriately-sized paper strips to the shim to thicken it slightly.  Five minutes with some Pritt-Stick, scissors and an old till-receipt was enough to prepare the existing shim for testing.  I reinstalled the shim and screen, and took several hundred (!) test shots.  The situation was now bearable but the back-focussing problem was still present enough to be annoying.

Back to the cutting-board I went, this time removing the paper strips and replacing them with similar sized strips cut from a used rail-ticket, as that was about double the (estimated) thickness of the original paper strips).  Pritt-Stick, scissors and patience were still the tools of choice.  Eventually I put it all back together and “Hurrah!” – manual focussing with the split-prism now works even more accurately than auto-focus.  Problem solved!


Despite, and perhaps even because of, the work I’ve had to put in to get things calibrated properly I’m now very pleased with the end result.  I now have a camera that still works very well with autofocussing lenses, but also has the capability to give me even sharper results with manual focussing.

I would heartily recommend such a screen upgrade to anyone who is struggling with manual-focussing their modern DSLR rig, but I would perhaps suggest that they buy an official screen either from the camera manufacturer (Nikon, in my case) or a much more trusted third-party manufacturer such as the Katz-Eye products linked earlier in the article.

With all of that said, I cannot vouch for either of these more expensive solutions as I have not tried them – so as always your mileage may vary.

Adventures with new camera gear

Pic:  Macro shot of focus markings on my newly-acquired Nikkor 135mm f3.5 lens. (C) Chris Ferguson
Pic: Macro shot of focus markings on my newly-acquired Nikkor 135mm f3.5 lens. (C) Chris Ferguson

So it was my birthday, and I’d been given some beer-vouchers for the privilege.  Thing is, I can drink beer pretty much anytime I want, so I decided to put the cash towards something a little more useful.


For a long time now I’ve been feeling somewhat limited in my photographic tools.  Not that I want to fall into the all-too-common trap of letting the tools define my work, but from a very functional perspective I was feeling that the Sigma 28-300mm zoom lens I’d carried from my first Nikon SLR kit to be somewhat lacking in some areas.

Sure, the Sigma takes more than reasonable pictures, but it’s a slow lens when used anything longer than 28mm, I’m not entirely enamoured with its colour handling.  The biggest problem I have with it however is that it’s a real pain to focus manually; the focus ring doesn’t need to be turned very far to get from closest to furthest distance settings, making precision a thing that is guessed at rather than measured.  Oh, all of that, and the damn thing changes focal length or focal distance when I’m adjusting the other parameter.

The other area of photography that interested me a lot when I had a compact camera capable of such shots, is macro (close-up) work.  It’s amazing what detail there is to be found in all manner of everyday objects, people, flora and fauna.  Looking in more detail at these not only gives fascinating images, but an even more fascinating insight into the designer of said subjects – the same truth applies whether we consider said designer to be God or Man.


A couple of years ago I bought my first prime lens – a fixed 50mm model that with its reasonably wide-open aperture of f1.8, it gathers enough light to use indoors at reasonable ISO’s and shutter speeds, without flash.  This lens was a revelation.  Not only did it open up a world of new photographic opportunities, its overall quality (and the quality of the shots it produces) is far above the standard kit lens that came with the D40.  The only downside?  Manual focus only, as it lacks a built-in focus motor.  No big deal for me, since I’ve come to prefer manual focus anyway.

Just before Christmas last year I found an elderly Vivitar 28mm lens, mentioned elsewhere on this site.  Again, the clarity and sharpness of the lens far exceeded either of the zoom lenses in my kit, and allowed for indoor shooting without flash.

Both prime lenses feature stiff, half-turn (or more) focus rings that allow far greater precision than either of the zoom lenses.  I would guess that this explains why the prime lenses have given much sharper shots than their zooming counterparts.


I can do wide work with the 28mm lens, and the majority of my work with the 50mm lens – but all too often I was having to swap out to the Sigma lens (and deal with all of its shortcomings) because I needed a bit more “reach”, or to make portraits that looked slightly more natural.  In the end, I would avoid any portrait shots as I didn’t want to take such terrible pictures of the subject!

I also worked out that all too often I really needed a zoom range somewhere in the middle of the Sigma’s range, but would end up setting it to the full 300mm not only because I could, but also because the lens tends to slip away from where I want it if I’m taking a photo at anything other than purely horizontal perspective.  Aim high or low and the lens wanders.  Terrible.  So what I needed was:  A lens in the 100-150mm range, with an appreciably wider aperture than the Sigma, and with better control over focussing – like the other two prime lenses.

I did some research during a much-needed day off work, mostly by looking at Pixel Peeper and Flickr.  Both these sites allow the user to search for specific lenses, and will show images registered as having been taken with them.  This allowed easy comparison of various options from Nikon, Sigma, Panagor and Hanimex.  I eventually saw that pictures taken by the Nikon lens were sharper than most others, and seemed to have a more pleasing tonal/colour quality than the others.  That said, the Nikon lenses were more expensive and the others did tend to give better contrast.

So I wound up looking around the Internet for used camera stores in London stocking the Nikon 135mm f3.5 lens, and found plenty of examples for around £50-£100 depending on age and condition.  At the same time, I also was looking for a reversing ring, which would allow the mounting of my existing 50mm lens backwards onto the camera body.  This allows the lens to work as a macro lens, focussing on subjects around 6-9 inches away from the lens.


The research basically led me to look at two stores, one in London and one in Croydon.  The London store, Grays of Westminster, looked to be the “gold standard” of used camera-gear stores and had a very good range of lenses in store.  I sent them an email one morning and they hadn’t got back to me by the end of that day, so I looked elsewhere.  This latter search led me to Mr Cad in Croydon.

Eventually Sarah and I took a trip to Mr Cad, and found a veritable Aladdin’s Cave as our reward.  This store is about 10mins walk away from West Croydon rail station, and run by a guy whom I can only describe as a friendly mad professor.  He’s been in the business for years, specialises in old film-based photographic gear, and clearly knows more than his fair share of the business and the practise.  On the advice of his assistant, Mike, I was able to try four lenses.  Two of these were Nikon-made (one “Q” version, the other was “QC” which was newer and deployed technically better optical coatings than the older “Q” lens), and the other two came from Panagor and Hanimex.  It was clear in the end that the Nikon lenses were better, and that with my gear, in that store on that day, I was unable to tell the difference between the “Q” and the more expensive “QC” lens.  I decided to buy the cheaper lens, as well as a reversing ring found on a nearby shelf to scratch the “macro” itch.

The lens I purchased looks from research to have been made sometime in the 1960’s, and has a lovely weighting, turning a range of around 300 degrees to focus between 4.5 feet and infinity.


Okay, so the only thing to prove was that “I’m right” – in that having done the research, the results of the products themselves matches the promise of what I found elsewhere.  Well as it happened we were blessed with a day of wonderful weather – sunny, but with some occasional cloud cover and a very light haze in the distance.  The results of the 135mm testing are here.  I also managed to get some macro shots in when I could persuade myself to let go of the 135mm for a few moments – results of *that* testing are here.

I’m very happy with the purchases, and am very much looking forward to further getting to know the new lens!