For Faster BIF focusing.

[Roland Karlsson]

I tried it with my 28-105/3.5-5.6. No matter what focal length and no matter starting or end point. It always move in the right direction. I tried the best I could, but could not make it go to nearest and then back again.

Read the OP again. We are talking about BIF shooting with 300mm or longer lenses.

Yes, I know. I was not clear enough. Just wanted to test if an ordinary lens also had the problem.

 

[Roland Karlsson]

I've had to do this a lot. And it's frustrating, because it isn't necessary. If they just set the focusing algorithm's fallback behavior to default toward trying infinity first, instead of trying close focus first, we wouldn't have to manually intervene, and we'd miss a lot fewer shots.

It seems like a brilliant idea to towards the opposite if the image is totally unsharp.

 

[paulkienitz]

I've had to do this a lot. And it's frustrating, because it isn't necessary. If they just set the focusing algorithm's fallback behavior to default toward trying infinity first, instead of trying close focus first, we wouldn't have to manually intervene, and we'd miss a lot fewer shots.

It seems like a brilliant idea to towards the opposite if the image is totally unsharp.

But with long lenses, the most common reason for being "totally unsharp" is just that the subject slipped out of the viewfinder for a moment. The focus hold settings help reduce the problem, but still, if it starts racking, 95% of the time the right thing to do will be to go toward infinity, because usually both the wrong and the right focus positions are closer to infinity than they are to the near side. And if you really do want to bring the focus back from the horizon to something nearby, there's no hurry about it.

 

[Roland Karlsson]

But with long lenses, the most common reason for being "totally unsharp" is just that the subject slipped out of the viewfinder for a moment. The focus hold settings help reduce the problem, but still, if it starts racking, 95% of the time the right thing to do will be to go toward infinity, because usually both the wrong and the right focus positions are closer to infinity than they are to the near side. And if you really do want to bring the focus back from the horizon to something nearby, there's no hurry about it.

You have got a point there. In the best of worlds, the lens would not change focus if there is nothing to focus at. But, in the real world, that is difficult to know.

BTW - I was out photographing with my K-1 seriously for the first time on Monday. I was using the 3x3 detector mode, which I thought would be nice. My usual mode is one point only, possible moving it from the center.

I have no idea what I did wrong, or if it actually was the camera that did choose the background over the person.

Surprise! I thought I was good at this

 

[paulkienitz]

But with long lenses, the most common reason for being "totally unsharp" is just that the subject slipped out of the viewfinder for a moment. The focus hold settings help reduce the problem, but still, if it starts racking, 95% of the time the right thing to do will be to go toward infinity, because usually both the wrong and the right focus positions are closer to infinity than they are to the near side. And if you really do want to bring the focus back from the horizon to something nearby, there's no hurry about it.

You have got a point there. In the best of worlds, the lens would not change focus if there is nothing to focus at. But, in the real world, that is difficult to know.

You could at least stick in a heuristic where, if suddenly there's nothing to focus on but the background looks like sky, then be especially reluctant to start racking.

 

[Roland Karlsson]

You could at least stick in a heuristic where, if suddenly there's nothing to focus on but the background looks like sky, then be especially reluctant to start racking.

Yep, but take this possibility.

1. The lens has focused on some far a way bird.
2. You see a much closer one and try to catch it.
3. Unfortunately, the long tele lens has a very shallow DOF.
4. So, that nearby bird is just blur.
5. The camera decide to either not focus or to go to infinity.
6. It is impossible to take a picture of the bird, without any manual intervention.

 

[paulkienitz]

You could at least stick in a heuristic where, if suddenly there's nothing to focus on but the background looks like sky, then be especially reluctant to start racking.

Yep, but take this possibility.

1. The lens has focused on some far a way bird.
2. You see a much closer one and try to catch it.
3. Unfortunately, the long tele lens has a very shallow DOF.
4. So, that nearby bird is just blur.
5. The camera decide to either not focus or to go to infinity.
6. It is impossible to take a picture of the bird, without any manual intervention.

The lens racks to infinity and then racks back toward closeup. The unwanted rack toward infinity costs little time because your previous position on the focusing ring was close to infinity and it hits the stop after only a short travel.

It doesn't matter much which direction you go if the current position and the desired position are far apart. What I'm trying to avoid is the situation (which I encounter all the time) where the current position and the desired position are close together, but the lens travels between them by going the long way around instead of the short way.

Macro photographers would want to switch the setting so it defaults to racking close first.

If the camera had data on what the current location of the focusing ring is (as it does in many other mounts, but not ours), it should default to whichever end is closer.

--
"A good photograph is knowing where to stand." -- Ansel

 

[Roland Karlsson]

You could at least stick in a heuristic where, if suddenly there's nothing to focus on but the background looks like sky, then be especially reluctant to start racking.

Yep, but take this possibility.

1. The lens has focused on some far a way bird.
2. You see a much closer one and try to catch it.
3. Unfortunately, the long tele lens has a very shallow DOF.
4. So, that nearby bird is just blur.
5. The camera decide to either not focus or to go to infinity.
6. It is impossible to take a picture of the bird, without any manual intervention.

The lens racks to infinity and then racks back toward closeup. The unwanted rack toward infinity costs little time because your previous position on the focusing ring was close to infinity and it hits the stop after only a short travel.

Now I am a bit confused. My post was an answer to yours where you did NOT want it to rack. I then described what could happen. It could get locked and not focusing.

 

[brandrx]

Hi Folks,

Always be ready for a BIF (actually most any kind of shot) by pre-setting your lens near infinity to be ready for the shot.

When you point your lens in the direction of the subject you want to take then if the definition of what you are pointing at is such that it shows very little definition then the Pentax camera will attempt to go to minimum focus first then back towards infinity. If you first set your lens towards infinity then the definition of most subjects will be such that the Pentax will go directly to the subject to lock on.

Test it out yourself with your 300mm or longer lenses. Set to infinity to be ready for BIF. Then keep track if you lock on to your subject faster all the time.

FWIW: I tested the above again today using a Pentax k-5IIs and Sigma 400mm f/5.6 Tele-macro lens. It works the same as I wrote in the OP. In doing the test I manually set the lens to 10 feet then pointed at subjects of about 40 feet, then 75 feet, then 100 feet, and finally 250 feet. In each case, the focus first went to minimum of about 5 feet then focused towards the subject to lock on. From 10 feet to 5 feet is about 1/4 turn. This focusing first to minimum then back to the subject takes a very long time. Lastly, manually setting the lens to infinity prior to attempting autofocus on the subject was much, much faster.

Ron

--
Ron - 'We don't have time to go take pics this afternoon Carl.'
Carl - 'What do you mean? It will only take 1/1000s.'
'Keep your eyes looking forward. However, glance back now and then to see where you've come from. It will put a smile on your face.' ~ brandrx

 

[audiobomber]

FWIW: I tested the above again today using a Pentax k-5IIs and Sigma 400mm f/5.6 Tele-macro lens. It works the same as I wrote in the OP. In doing the test I manually set the lens to 10 feet then pointed at subjects of about 40 feet, then 75 feet, then 100 feet, and finally 250 feet. In each case, the focus first went to minimum of about 5 feet then focused towards the subject to lock on. From 10 feet to 5 feet is about 1/4 turn. This focusing first to minimum then back to the subject takes a very long time. Lastly, manually setting the lens to infinity prior to attempting autofocus on the subject was much, much faster.

Anyone who wants to argue with you should do the test themselves, not just mouth off about it.

I always reset to infinity, and that works for me. If I'm shooting in macro range, I don't use AF.

 

[Barry Pearson]

FWIW: I tested the above again today using a Pentax k-5IIs and Sigma 400mm f/5.6 Tele-macro lens. It works the same as I wrote in the OP. In doing the test I manually set the lens to 10 feet then pointed at subjects of about 40 feet, then 75 feet, then 100 feet, and finally 250 feet. In each case, the focus first went to minimum of about 5 feet then focused towards the subject to lock on. From 10 feet to 5 feet is about 1/4 turn. This focusing first to minimum then back to the subject takes a very long time. Lastly, manually setting the lens to infinity prior to attempting autofocus on the subject was much, much faster.

Anyone who wants to argue with you should do the test themselves, not just mouth off about it.

I always reset to infinity, and that works for me. If I'm shooting in macro range, I don't use AF.

For the interest of those who haven't used one, the D FA 150-450mm lens has the option of storing a preset focusing distance, with 4 buttons around the lens to go straight there. I have rarely needed to use it, but it appears to be just right for the advice being given here.

(And I like the limiters on the D FA 70-200mm and D FA 150-450mm lenses. They have the options of, in effect, far-away, close-up and none. Although, to be honest, in my experience they rarely hunt).

 

[paulkienitz]

You could at least stick in a heuristic where, if suddenly there's nothing to focus on but the background looks like sky, then be especially reluctant to start racking.

Yep, but take this possibility.

1. The lens has focused on some far a way bird.
2. You see a much closer one and try to catch it.
3. Unfortunately, the long tele lens has a very shallow DOF.
4. So, that nearby bird is just blur.
5. The camera decide to either not focus or to go to infinity.
6. It is impossible to take a picture of the bird, without any manual intervention.

The lens racks to infinity and then racks back toward closeup. The unwanted rack toward infinity costs little time because your previous position on the focusing ring was close to infinity and it hits the stop after only a short travel.

Now I am a bit confused. My post was an answer to yours where you did NOT want it to rack. I then described what could happen. It could get locked and not focusing.

OK, I think I get you now -- you're worried that if you put in a no-rack heuristic, it might fool the camera into not focusing at all when you try to switch to a nearby subject. I guess that's a legitimate worry. I thought originally that it should not be difficult to distinguish the sky from any other background, but that could be fooled by shooting across flat water which reflects the sky. Aim at a nearby duck, or a dragonfly on a twig, and nothing happens. So yeah, that idea might not work.

--
"A good photograph is knowing where to stand." -- Ansel