How the hell do you focus those manual focus lenses on modern DSLRs? Very carefully....

The finest lens design in the world is pretty meaningless 

unless you have a plan to focus it well. 

I've been writing a lot recently about my admiration for older Nikon lenses and my tendency to select older, manual focus-only lenses in my day to day work. To recap: I am currently making good use of the Nikkor 25-50mm f4.0 zoom lens, the 55mm f2.8 micro Nikkor, the Rokinon 85mm t1.5, the Nikon 105mm f2.5, and the Nikon 135mm f2.0 lenses on my two Nikon DSLRs; the D810 and the D750. I'm pretty sure that anyone who has tried to just pull up a modern digital camera to their face and focus an older lens quickly will tell you that the (non)focusing screens in all the modern cameras are pretty much crap for manual focusing. The screens are optimized for visual brightness but not for the acuity necessary to discern (accurately) sharp focus. What's a guy to do?

Some one asked this morning if I had a trick to using these lenses and if the whole focusing issue with manual focusing lenses and DSLRs is overblown. No and no. I wish I had some special trick to nail sharp focus every time but I don't. And since I don't have a trick then, no, I don't think this design fail in modern finders is overblown. That being said I am certain that the vast majority using DSLRs are using them exclusively with auto focus lenses. 

In real life, each of the lenses I use is handled differently. If I am using the 24-50mm lens it's usually outdoors and I'm using the wide end of the lens to capture a scene or a building or something that asks for wide angle. If it's Austin/Texas blue sky sunny I just zone focus with that lens. The beauty of the older lenses is that they usually have very well done focusing scales that are very accurate. Much more accurate than the focusing scales on the new lenses. The single focal length lenses even have hyperlocal distance markings on the barrels which give you another advantage. 

So, if I'm walking around downtown with the 25-50 I might have the camera set to M or A and the lens set to f11. I know from looking at a lot of depth of field tables over the years that by setting the lens at eight to ten feet on the focusing ring that, in the 25-30mm range, I'll have sharp focus from infinity down to about five feet. If I'm really concerned about high sharpness of objects closer to infinity I'll move the focusing ring closer to between 15 and 30 feet. I know with certainty that anything further than 20 feet that I point my camera at will be in sharp focus. I don't have to fine tune for each frame. The depth of field covers it well. 

If I am shooting out on the street with a 35mm MF Nikon I might set my aperture ring to f11 and if I put my infinity setting on the yellow, color coded line on one side of the center focus hash I can look on the other side of the corresponding yellow hash mark and see that I can be reasonably in focus from about 8 feet to infinity. I can walk through the streets and shoot with abandon, knowing that anything in that range will be in focus. 

That takes care of a lot of wide angle stuff but what about the longer focal lengths? Well, first of all I think that very fast. longer lenses give you a certain advantage because, unlike the wider lenses, the apparent focus wide open tends to pop and in and out with more certainty. It's one of the reasons faster lenses were so popular back in the manual focus only days. The "in focus" was more apparent with the brighter lenses and the narrower depth of field. Win, win. 

When I shoot with the medium telephotos in the studio focusing is definitely an issue. Bugs the hell out of me. But when I shoot portraits in the studio I am almost always using a tripod. I use a tripod because it helps me to "anchor" a composition but also because I like to use continuous lighting and a tripod allows me to use slower shutter speeds than I can normally hand hold. If I am using a tripod then with both of my current DSLRs I can go into "live view" and punch in to see a magnified section of the image and really fine tune focus. I also tend to shoot about one f-stop smaller than I might with an AF lens. Instead of shooting the 105mm wide open I might use it at f3.5 instead. It's not much but I'm hoping to cover myself, at least a little bit. 

In each of the Nikons I use there is a three light system of focus confirmation that can be very useful. The issue I have with it is that it's too undiscerning. There's a green arrow on either side of a center dot. If one the arrows lights up then you are out of focus and, supposedly, when the center dot lights up you are in focus. My issue is that the center dot stays lit though a bit of travel of the focusing ring. In other words the indicator is very lenient as to what is in and out of focus. I conjecture that the system was devised with the idea that most people are shooting at f5.6 or f8 and that depth of field will cover them. But I don't shoot that way.

What I have found though is that each camera tends to help me back focus just a little bit when I wait until I hit the center spot of the green confirmation light exactly. I have experimented quite a bit and now I use the "too close" arrow and the "confirmation dot" in tandem. My goal with longer telephoto lenses (85-200) is to hit just at the spot where the "too close" light and the "confirmation dot" blink back and forth and then give a tiny nudge until the green dot wins. At that point I can shoot wide open with reasonable certainty of getting the shot. 

If I am shooting for my own enjoyment I am okay with trusting this dancing dot method and I find it pretty quick to shoot this way in the field. If my kid was running a cross country race I would rely on a different method if I wanted to shoot close to wide open. 

If I am photographing a real sporting event (swimming or running) and want to use a manual focus lens I rely on refocusing at specific points. If Ben were to run by in a race I would have a focus point in his path that I had prefocused on with one of the above methods, this way I would be able to concentrate on just shooting rather than managing an AF sensor or trying to "spin the ring." In a group of runners it's almost impossible to keep an AF point where you want it and pre-focusing can give you more keepers. 

But realistically, I use the MF lenses mostly in controlled situations and mostly when using a tripod. I compose the shot, switch to live view and punch in to a magnified view to attain perfect focus and then I switch out of live view to viewfinder mode and shoot until I change position or my subject moves. The added benefit is that I am focusing at my taking aperture which eliminates the chance of optical focus shift upon stopping down. 

When I am shooting fast moving stuff the optical benefits and characteristics of the MF lenses; the qualities I like them for, are secondary to getting the shot. In these kinds of jobs I don't have so much hubris that I risk outrageous failure so I am quick to switch over and use my lenses with AF. The 24-120mm replaced the 25-50mm and the 80-200 replaced the 85, 105 and 135. They get the job done. 

So, there are reasons to use both. My green dot method works for me most of the time and if I didn't do this for money and clients I would be comfortable using the MF lenses all the time. In nearly every situation I come across there's ample time to work on focusing. And who knows? With enough practice I may yet be able to focus accurately on the screen of a D810.  But I wouldn't count on it....

Rule of thumb. It's better to focus once and lock it down than to keep refocusing. Subjects don't move as much as one might think. That being said, if your photography depends on sharp images of moving objects with shallow depth of field then you might want to relegate your MF lenses to some other tasks and go with the sure thing.

Look versus reliability.

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