[menappi]

Ok so I picked up a smc-m 50 2 off the boards and I love it compared to my kit lense (k100d) but i've noticed some pictures aren't coming out as crispy as I had expected, or seen in exaamples online. I'm wondering if anyone has any tips on focusing this thing or how to achieve optimal image clarity.

Stopping down will increase the quality right? (f/2 on this lense seems kind of soft to me as i've seen it)

As far as I know, I usually wait for the little green focus indicator to beep in the viewfinder to alert me of a focused image..is this full proof? Sometimes it's just too hard to tell by looking in the viewfinder but i usually go by the green light.. (is this good practice?)

Maybe I should of gotten the 1.4/1.7.. and also, I don't plan on dropping any large amounts of money on a focus screen. Can something like that be had for under 50 bucks? Do I even need it?

[johninmula]

This item was written some months ago in DPreview Pentax forum, it may help

Manual focus tutorial

It's much easier to teach focusing in person. Writing up a procedure to do it is tedious. Happily, with a digital camera, it is easier to practice without wasting a ton of film in the process.
Here's a short sequence to experiment with:
- Start easy: Pick a medium focal length lens, like 50-70mm, and preferably a fast lens. (you can do it with a zoom set to this focal length too.
- Place a target about 2m away, separated from foreground and background. The target should be something with some surface texture to work with, or something with a mix of 6, 9, 12, 14 and 18 point font on it. Light it adequatelly for a wide open aperture and short exposure time (like 1/200 second). Lock in the exposure manually so it cannot vary on you.
- Get comfortable with the camera and set it to MF mode.
- Twist the focusing ring from infinity to closest focus at a medium speed. Then the other direction after a short pause. And again and again. Do it slow enough that you can watch the focus transition from blur to sharp to blur, but fast enough that the transition to critically sharp "pops" for a moment as you turn. OBSERVE the focus transition carefully, over and over again. Get a feel for how much time/how much angular displacement of the focusing ring causes how much focus transition to occur.
The trick is to look at a subject and know the lens well enough to turn the focusing at the speed which makes the sharp moment pop, and be able to stop PRECISELY at that point.
- Start trying to achieve that point of focus ... only turn in one direction and try to stop just once, make an. exposure. DON'T look at it immediately on the LCD ... it helps if you turn off the review function. You want to repeat from close limit and from infinity ten times each.
- Then download the image files to your computer and sort them into frame order. Look at them, one at a time, at 1:1 pixel resolution and mark down which are in focus and which are slightly off. Try to remember for each one what you felt as you stopped and made the exposure.
Repeat this exercise until you get nine frames sharp. Then repeat it again doing 20 frame sequences until you get 19 frames sharp. Do as many as you can but DON'T keep going until you get tired, stop and take a break for a little while. The point is to plant in your finger and eye memory how fast to turn the ring and how to stop instantly when you see the point of best focus, just once.
- Once you're doing sequences of 20 shots and getting them all in focus, double the target distance with the same lens and do the same exercise over again. Once you get 20 out of 20 with that repeatedly, you can double the distance again. It gets faster as you go along. By the time you get there, you should set up two more targets so you have three ... 2, 4, and 8m ... and do a couple of sequences where you focus on each one at a time ... put it in the center of the frame so you know which your focusing on ... and do the same sequence of 20 until you get them all in focus through the sequence repeatedly.
So now you know what it's like to focus that lens quickly and reliably, with your eye alone.
- Change the lens to a shorter focal length (say 28 to 35mm). Start at the beginning but use 1.5m as a starting point. Same rig, same target, different focal length ... the shorter the focal length, the more subtle the focus transition is to observe.
- Keep doing the sequences with shorter and shorter lenses until you get to the shortest lens you have. Realize that when you get down to the 18-20mm range, you have to accept either a slower pace or a few more erroneous focusing frames to "finish" a sequence.
This kind of skill does not take exceptional eyesight; it takes the ability to see the motion of the focus transition 'stop' or pop for an instant and the muscular ability to stop turning the focus ring precisely at that instant. I've been able to get perfect critical focus using it even when my glasses were covered with guck after a hot session on a sweaty day or I dropped them and could not stop taking photos for one reason or another. All you're looking for is that point of "pop" in focus as the image moves a tiny bit, and to stop your fingers at that moment, you're not trying to see the details.
I'm sure that if you go through this exercise with calm motivation, you'll find your manual focusing reliability improve ten fold in a day. I've been doing this so long and with so many different cameras that it just seems to come naturally to me. First thing I do whenever I fit an unknown lens to my camera is switch to MF and just rack it in and out from infinity to close limit focus a couple of times to "calibrate" my eye and fingers. Within a few moments of that, I'm ready ... I rarely get a bad focus, if I bother to look through the viewfinder and focus at all ...

[Marc Sabatella]

Stopping down will increase the quality right? (f/2 on this lense seems kind of soft to me as i've seen it)

Yes, although you may also be missing focus more than you are realizing. The biggest issue with manual focus using "fast" (f/2.8 or better) lenses with Pentax DSLR's is that the DOF is very small - and in fact, much smaller than it looks in the viewfinder. Here's a very simple test, and something to practice with:

Lay out a sheet of newspaper or something similar on a table. Aim your camera at it so you're looking at the text at a 45 degree angle. Open up the aperture as wide as it goes. Focus on a particular line of text. Note how many lines of text in front and in back of that line are in focus enough to read. Now take the picture, and look at it on the LCD. You'll see many *fewer* lines are in focus - and the line you thought you were focusing on might be among the lines no longer in focus.

Practice learning how to focus so that the line you care about remains in focus. For me, that means making sure there is more in focus *behind* my target than in front.

As far as I know, I usually wait for the little green focus indicator to beep in the viewfinder to alert me of a focused image..is this full proof?

I find it not all that reliable, but I do check it sometimes.

also, I don't plan on dropping any large amounts of money on a focus screen. Can something like that be had for under 50 bucks? Do I even need it?

You might find the Pentax O-ME53 magnifying eyecup to be of help, and if is under $50.

[konraDarnok]

I had a terrible time manual focusing until I fixed my camera's back focus issue.

I hate to even bring that up, but if you're using Marc Sabatella's technique of photographing a news paper (or book) at 45 degrees -- and you see more lines of text are in focus above the line you're focusing on than below that line, you've probably got a back focus issue. (get as close as you can for this test)

IMHO, with that green hexagon lighting up at f/2, you shouldn't be getting that many blurry photos -- at least not ones that can't be attributed to camera shake or other non-focus issues.

DOF get's much thinner with smaller aperture numbers under f/2. And I can get reliable focus at f/1.2 with that green hexagon when the camera's operating properly.

For example, this is at f/1.2 I'm focusing on 'He' (with full pixel inset to the left) -- relying on nothing but the green hexagon.



You should be getting a similar result at f/2 but there should be more lines of text in focus (the DOF will be greater). If you are, just keep practicing. If you're not . . . . you'll be back asking how to fix this.

---

Last edited by konraDarnok; 11-11-2008 at 11:31 AM.

[PDL]

Use AF as a starting point. De-couple AF from the shutter button - so YOU have the final say - not the camera.

With Pentax Lenses - using quick shift - once AF has "locked" (I use the AF button on the K10D and K20D - the OK button on the *istDs) rock the focus back and forth, your eye will tell you when to stop. And the eye is very good at doing this.

When using non-quick shift AF lenses (I have the FA 50mm f1.4 and a Tokina 28-70mm) - with AF engaged - if you turn the focus ring, you can damage the camera since you are making the AF motor spin by twisting the focus ring. Those gears/motor are not designed to be twisted like that. If you insist on using manual focus (not a bad thing to do) make sure that the switch on the front of the camera is set to M - which retracts the AF screw in the mount and disables the AF motor. Then use the technique described above - rock back and forth using your eye to determine the focus. Note: You can - if you have decoupled AF from the shutter button - press OK/AF and the AF circuit will help you by flashing the green hexagon in the viewfinder.

For pure manual lenses (I have a old late 70's 300mm f5.6 Vivitar), set the focus switch to M and press the AF button for AF assist. Then use the rocking method to let YOU decide if the object of interest is in focus.

Rely on your brain - not the silicon decision makers in the camera.

A little history - I learned this technique by using TLR's, 4x5's and a Exa SLR that had only ground glass screens - no AF, no split image, no micro diamonds - it has worked well for the last 50 + years, works now. The only thing is, you have to practice - take shots that you are willing to blow away as learning examples. If you are going to try this - without practice - on something important ---- well, I just expect you to be another among those who b*tch about AF not being good enough and you are jumping ship.

The Elitist - formerly known as PDL

[Marc Sabatella]

I hate to even bring that up, but if you're using Marc Sabatella's technique of photographing a news paper (or book) at 45 degrees -- and you see more lines of text are in focus above the line you're focusing on than below that line, you've probably got a back focus issue.

That's sort of true, but also kind of misleading. For one thing, when people speak of backfocus, they are generally talking about autofocus, not manual focus. If your camera has consistent BF with manual focus, this is a matter of the the focus screen being misaligned relative to the sensor (or vice versa). It has nothing to do with anything that can be fixed with the focus adjustment menu on the K20D.

Second, it's actually *normal* for more to be in focus behind than in front - that's the nature of optics. Although the convention that says it should be 2/3 in back, 1/3 in front is overly simplistic - it really should be much closer to 50/50 than that at most focal lengths.

But most importantly, the fact that the viewfinder will always show *more* being in focus than actually is going to end up in focus in the picture means that iot is kind of pointless to talk about how much is in focus in front of versus in back of the main focus point, because the viewfinder gives you no way to actually be sure what the main focus point is. It's showing you a broad area and saying "the main focus point is somewhere in here", but that's as far as you can tell.

That is, you might be *aiming* for a certain line of text, and the viewfinder might be showing it to you as in focus, but that doens't mean it is actually the mian focus point - the viewfinder is showing you *several* lines that are in focus, and you really have no way of knowing - aside from performing this test and practicing - which of them is actually the main focus point.

The only way you can really say a camera has a BF problem with manual focus is if things are in focus in the picture but *not* in the viewfinder when shooting wide open. That's pretty rare.

[konraDarnok]

That's sort of true, but also kind of misleading. For one thing, when people speak of backfocus, they are generally talking about autofocus, not manual focus. If your camera has consistent BF with manual focus, this is a matter of the the focus screen being misaligned relative to the sensor (or vice versa). It has nothing to do with anything that can be fixed with the focus adjustment menu on the K20D.

Second, it's actually *normal* for more to be in focus behind than in front - that's the nature of optics. Although the convention that says it should be 2/3 in back, 1/3 in front is overly simplistic - it really should be much closer to 50/50 than that at most focal lengths.

But most importantly, the fact that the viewfinder will always show *more* being in focus than actually is going to end up in focus in the picture means that iot is kind of pointless to talk about how much is in focus in front of versus in back of the main focus point, because the viewfinder gives you no way to actually be sure what the main focus point is. It's showing you a broad area and saying "the main focus point is somewhere in here", but that's as far as you can tell.

That is, you might be *aiming* for a certain line of text, and the viewfinder might be showing it to you as in focus, but that doens't mean it is actually the mian focus point - the viewfinder is showing you *several* lines that are in focus, and you really have no way of knowing - aside from performing this test and practicing - which of them is actually the main focus point.

The only way you can really say a camera has a BF problem with manual focus is if things are in focus in the picture but *not* in the viewfinder when shooting wide open. That's pretty rare.

That's all true; I'm mostly talking about the green hexagon for manual focusing tho. I personally find the matte screen to be a difficult focusing aid. And per my experience, if the green hexagon is giving false positives in manual focus, you'll get the exact same focus discrepancy in auto focus for large apertures.

So to preface my previous post, if you're relying on the auto focus system to confirm manual focus (per the green hexagon), it's best to make sure it's calibrated properly.

I'm identifying with the poster. Last year I was going nuts with my manual focus problems. It was *very* frustrating.

Nothing is a substitute for experience -- and I took thousands of frames before I was confident that I wasn't blind or practicing poor technique -- which is often the response when a person new to SLR photography is asking about why they can't achieve proper focus.

Only menappi can be confident their doing everything properly. But, it really shouldn't be difficult to achieve proper focus at f/2 IMHO.

---

Last edited by konraDarnok; 11-08-2008 at 02:39 PM.

[Marc Sabatella]

That's all true; I'm mostly talking about the green hexagon for manual focusing tho. I personally find the matte screen to be a difficult focusing aid. And per my experience, if the green hexagon is giving false positives in manual focus, you'll get the exact same focus discrepancy in auto focus for large apertures.

So to preface my previous post, if you're relying on the auto focus system to confirm manual focus (per the green hexagon), it's best to make sure it's calibrated properly.

Ah, yes - that makes perfect sense.

[creampuff]

The first thing to do is to set the diopter correction at the viewfinder to your shooting eye.

[Canada_Rockies]

The first thing to do is to set the diopter correction at the viewfinder to your shooting eye.

And that is best done with a blank target - pure white is the best. Put the diopter slide where the lines on the focusing screen are the sharpest. The lines on the focusing screen, nothing else. The LCDs along the bottom might not be at exactly the same distance as the focusing screen.

Close your eyes and try again. Keep doing this until when you open your eyes again, the lines are sharp. That will give you the best position for the diopter for you. I will often simply look straight up into the sky to do this, but even a lamp shade will work, or the front of your fridge.

You may also find that your eyes will see differently under dim light than bright light. If you are shooting in a club or a dim hockey rink, set the diopter for that lighting. You need to take into account the aperture that your eye is using as well.

I am coming up with cataracts, not uncommon at my age, and with age, your lens also gets stiff and does not focus as well as it used to - that's why you need reading glasses, gang. The cataract in my right eye is getting to the point that I think I will have to have it removed. I am starting to see double in that eye, and it is my shooting eye. The joys of aging - NOT.

[creampuff]

Diopter setting can simply be done by letting the camera AF to particular object. Once the object has been focused by the camera (and without shifting the camera's position), progressively slide the diopter switch above the eyepiece until the object appears sharpest in the viewfinder.

[Wombat]

I never cease to be amazed at the depth of knowledge on this forum. When I saw the thread, I thought, "Oh, I don't need to read that. If I can't focus properly after all these years I may as well give it up." But, as always, I learned something new to go and practise. You guys are amazing. Respec'!

[gowerray]

Another thing you want to consider is 'depth of field', the amount of the subject you want in focus. The nearer the subject, the narrower the DOF and therefore the narrow area of sharpness. Extreme example: Eyes crisp, ears blurred. Easy to do as some of my portraits will testify
Good link here for a better explanation and 'live' guide: Depth of field
Hope it helps, Ray

[Kerrowdown]

I bought a Katzeye focus screen, the proportion of my sharp focused shots went up in leaps and bounds, just a thought for you, anything thats gives you an edge is worth it, well IMHO that is.

[junglism]

wow johninmula thanks for a great post!!