My Technique for Manual Focus Lenses

[Youngster]

I have been using a technique with manual focus lenses which I have found to be extremely effective. Perhaps others have already discovered it and I am just rehashing, but I thought I would share it with everyone anyways.

I've been using the Pentax 50mm f1.2 lens for almost 2 years now. This lens has a reputation of being extremely difficult to use wide open, and I always had difficulty getting consistent sharp focus wide-open as well. The autofocus indicator helps a bit, but the range where it is "confirmed in focus" is too large and more often then not, completely unsuitable for the small DOF at f1.2. Unfortunately, my eyes aren't that much more consistent at focusing perfectly either. I suppose a split screen might have helped, but that had too many other drawbacks. Eventually I came up with the following methodology which I hope will be useful for others who are manually focused challenged as well:

Focus Bracketing using Catch-in focus and Continuous Shooting Mode

This is for my K20D, so please adapt it to your particular model.

0. Set to Av mode. (Might work in other modes, I just normally use Av.)

1. Turn on Catch-in-focus if you have it (it is in the custom menu).

2. Set your camera to Continuous Shooting Drive Mode (where you hold down the shutter and it shoots continuously).

3. Turn the focus knob to AF.S mode. (This is necessary to use catch-in focus)

4. Focus the subject with your eyes until it is almost within focus.

5. Hold down the shutter (it should not fire because object is not in focus). If it fires, you are either in focus or have it set up wrong.

6. Slowly turn the focus on the lens until the object is in focus and beyond.

7. If you turn it slowly, the shutter will fire 2-3 times in the "range" where the confirmed in focus light is lit up.

8. One of those shots should be almost perfectly focused every time. Sure you waste 1-2 shots each time, but better 1 out of 3 than 0 out of 1.

It has worked for me extremely well especially where DOF is very thin. It will work on all manual focus lenses including K and A type lenses. (Will not work with AF lenses unless you short the contacts). Unfortunately, this also does not work well with taped lenses (the one where you insulate the contacts to allow Av mode for the first three stops using K lenses)

Let me know how it works for you.

[timo]

Originally Posted by Youngster

I've been using the Pentax 50mm f1.2 lens for almost 2 years now. This lens has a reputation of being extremely difficult to use wide open, and I always had difficulty getting consistent sharp focus wide-open as well. The autofocus indicator helps a bit, but the range where it is "confirmed in focus" is too large and more often then not, completely unsuitable for the small DOF at f1.2.

Focus Bracketing using Catch-in focus and Continuous Shooting Mode

This is for my K20D, so please adapt it to your particular model.

0. Set to Av mode. (Might work in other modes, I just normally use Av.)

1. Turn on Catch-in-focus if you have it (it is in the custom menu).

2. Set your camera to Continuous Shooting Drive Mode (where you hold down the shutter and it shoots continuously).

3. Turn the focus knob to AF.S mode. (This is necessary to use catch-in focus)

4. Focus the subject with your eyes until it is almost within focus.

5. Hold down the shutter (it should not fire because object is not in focus). If it fires, you are either in focus or have it set up wrong.

6. Slowly turn the focus on the lens until the object is in focus and beyond.

7. If you turn it slowly, the shutter will fire 2-3 times in the "range" where the confirmed in focus light is lit up.

8. One of those shots should be almost perfectly focused every time. Sure you waste 1-2 shots each time, but better 1 out of 3 than 0 out of 1.

It has worked for me extremely well especially where DOF is very thin. It will work on all manual focus lenses including K and A type lenses. (Will not work with AF lenses unless you short the contacts). Unfortunately, this also does not work well with taped lenses (the one where you insulate the contacts to allow Av mode for the first three stops using K lenses)

Let me know how it works for you.

Is that better than just putting the camera on to manual focus and firing on burst mode while you gently turn the lens through the in-focus zone? Doing it this way might be better, as (say with flowers) it is never easy to be sure that the AF has hit the bit that you wanted. And you can use any lens. But I will try your suggestion with one of my M or K lenses.

Tim

[pschlute]

I use a split-prism focus screen and find it very useful.

Is the lens an A or the older SMC "K" ?

[ChooseAName]

I think I've used this technique before, or at least something like it. It's sort of like "focus bracketing," is it not? How is it different from what Tim described?

(not being snarky, I would like to know if I missed something in your post)

EDIT: sorry, you apparently called it Focus Bracketing in your original post.

[tarsus]

Thanks for the tip. I never really understood catch in focus before your post. It worked very well with a Vivitar manual lens.

[timo]

Originally Posted by pschlute

I use a split-prism focus screen and find it very useful.

My faith in split prism screens has been slightly shaken since I discovered that on my K10D not only was it generally backfocusing (improved by the illicit debug procedure) on AF; infuriatingly manual focusing even with a Katzeye screen was itself not spot-on. So I think I must have got a camera assembled near the end of a shift or something ...

On my new K7 things seem to be rather better, and I seem to be able to MF with reasonable accuracy with the original screen.

Tim

[Youngster]

Originally Posted by timo

Is that better than just putting the camera on to manual focus and firing on burst mode while you gently turn the lens through the in-focus zone? Doing it this way might be better, as (say with flowers) it is never easy to be sure that the AF has hit the bit that you wanted. And you can use any lens. But I will try your suggestion with one of my M or K lenses.

Tim

It is a bit better than putting it into manual focus and just firing because this way, it only fires when it is "sort of in" in focus without having to test your reflexes. You waste a few less frames. Unfortunately, with the K lenses, it only works wide open, but at least that is where one need sit the most.

[Youngster]

Originally Posted by tarsus

Thanks for the tip. I never really understood catch in focus before your post. It worked very well with a Vivitar manual lens.

Actually, I think they intended catch-in focus for catching moving subjects by pre-focusing on a certain area and when the subject passes through the area, it automatically takes a shot. It works suprising well for that purpose.

I just took advantage of the fact that it also works when the object is static and you turn the focus ring as well.

[opfor]

Originally Posted by Youngster

Actually, I think they intended catch-in focus for catching moving subjects by pre-focusing on a certain area and when the subject passes through the area, it automatically takes a shot. It works suprising well for that purpose.

I just took advantage of the fact that it also works when the object is static and you turn the focus ring as well.

I went out and tried static and moving subjects yesterday and today. For static subjects the key phrase is definitely bracket. It works well though. I have a DL with a focus screen and a k20 without. The bracket worked well when the light made it hard to use the focus screen.
The problem with moving subjects is the pre-focus. Definitely something I'm going to practice and get better at, I can see myself using this.
Thanks.

[Canada_Rockies]

Originally Posted by Youngster

Actually, I think they intended catch-in focus for catching moving subjects by pre-focusing on a certain area and when the subject passes through the area, it automatically takes a shot. It works suprising well for that purpose.

I just took advantage of the fact that it also works when the object is static and you turn the focus ring as well.

Pentax, contrary to most of the other camera companies, does not turn off the focus requirement when you use a manual focus lens. This dates back to my SF-1, where they called it snap-in-focus. Basically any manual focus lens you mount on your camera can be used in AF.S mode. The camera will only release the shutter when proper focus is detected.

With the K20d and later, you can also use it with the DA* lenses with MF/AF switch on the lens turned to MF, provided you enable the Catch-in-focus in the menus. At least that is what I gather from the manual. I wish it were true on my K10D, but it is not, unfortunately. Setting MF on the lens has exactly the same effect as turning the body to MF.

[dlacouture]

Only drawback of this method is that it works with the central point only with non-A lenses...

But it does raise an interesting point I never really considered : focus-bracketing is real cheap nowadays, so why not use it? I'll give it a try with my Porst 55/1.2...

[atelier7]

thanks for the tip. I can't wait to try it with a tak 50 f1.4 and 200 f4 i'm waiting for to arrive in the mail. i've got a k200d and k100DS. was thinking of getting a split prism focus screen but read about difficulties it sometimes presents so I'll happily work with what i've got rather than spend another $100 if possible.

[dadipentak]

Actually I stumbled on this technique myself quite by accident a while back but then forgot how I did it so this was very helpful, Youngster--thanks for spelling it out.

[dosdan]

A related problem is DOF in a flower shot, as mentioned in the thread. You usually can't tell with the K20D's viewfinder whether all the parts of a flower you want will be in focus well enough when you take a shot with a narrow DOF. I get caught out often on this. An example is the lower right of this flower shot:

http://www.pentaxforums.com/gallery/...7061_Large.jpg

I don't think there is an "Aperture Bracketing" in the menu, so with flower shots I think it is worthwhile taking another "safety" shot with 1 stop smaller aperture.

Dan

[Eruditass]

great idea, i should've thought of that instead of taking 50 OOF shots the other day, only to discover I put the shim on backwards!