front focus, back focus or other?

imfinetoday · 07-08-2010, 07:19 AM

Originally posted by Marc Sabatella

In the distant shots, it's pretty clear the camera is simply choosing to focus somewhere other than on your subejct. No big surprise there, since the subject isn't big enough from that distance to cover the whole focus sensor.

When you refer to focus sensor, are you speaking of the points in the viewfinder?

Parallax · 07-08-2010, 07:31 AM

The points are not exact, and the actual focus area for any given point is quite a bit larger than the indicator light. It is possible, in the more distant shots, that even if you select the center point, and set it right on your subject's face it may still focus on the scenery in the background. This isn't a defect in the camera. It is a characteristic that you just need to learn to compensate for; either by using MF, or learning what else to focus on.

JeffJS · 07-08-2010, 07:34 AM

Your posted sample shots look like a good opportunity to try Manual focus. AF is a tool, sometimes a great one, like all of the other features of your camera. However, sometimes it's better just to go back to basics.

imfinetoday · 07-08-2010, 07:52 AM

Originally posted by JeffJS

Your posted sample shots look like a good opportunity to try Manual focus. AF is a tool, sometimes a great one, like all of the other features of your camera. However, sometimes it's better just to go back to basics.

I've been thinking that. however, the times that i have tried manual, it's always come difficult for me. any helpful tips? is just something you have to take time to learn?

JeffJS · 07-08-2010, 08:25 AM

Originally posted by imfinetoday

I've been thinking that. however, the times that i have tried manual, it's always come difficult for me. any helpful tips? is just something you have to take time to learn?

I see you are using the K20d. If it were the Kx or K7 I would suggest Live View but even then it can become cumbersome. Some get a split focusing screen to help with manual focus (center spot is split at 90 or 45 degree angle and when both parts are perfectly aligned, the subject is in focus). Where I would suggest you start, is practice with what you have. Start close, see what perfect focus looks like, and then zoom or move further back. Make sure that you've set the diopter on the viewfinder for maximum sharpness of the lines on the screen (that's the way I set mine).

For what it's worth, you Could try the live view on the K20d. I didn't find it all that useful, or even accurate when zoomed in. Your experience may prove different.

In your samples, the others are right. Your lady friend (wife?) at the furthest distance is somewhat dwarfed by the actual AF area of the camera. It's reasonable, that the camera might pick the nearest high contrast area for AF. You Could try selecting a different point and focus / recompose but I don't know if the AF area is different on the other points. I do know they are different Types of AF sensor points (line vs cross). That or try center AF and select something she is standing next to. At that distance, even the fence behind her (if she's leaning on it) would be good enough.

Frustrating I know, I sometimes experience the same thing with my DA12-24 but I'm confident it is not the camera or the lens. It's me and my expectations.

hangu · 07-08-2010, 08:30 AM

Every day, it seems, someone makes a post complaining about their camera/lens being front/back focused.

The auto focus sensor is not human. It doesn't know if you're trying to shoot a portrait or if there just happens to be a bystander in the landscape you're trying to photograph. It does a decent job most of the time guessing which it is but it's not going to be right 100% of the time. That's just the nature of letting the camera do the work for you.

Back/Front focus is ALWAYS present no matter what distance the subject is from your camera. It's more obvious when the subject is closer, not farther away. Focusing errors is usually very small. If your main subject is really blurry and the focus is way off, it's almost definitely because you didn't choose the correct camera setting.

When using an under 40mm auto focus lens, it might be easier to focus on the foot/ground if the main subject is far away, especially if the ground is a grassy area with some contrast. The reason for this is that the area around the subject's foot is the largest area where distance is somewhat constant to your camera. With the long distance and wide focus length, the large depth of field should compensate just fine. It's not perfect but it's sure better than what you're pulling by focusing on the face. I usually focus on the torso/chest/crotch depending on which area is largest and has the most contrast.

imfinetoday · 07-08-2010, 08:47 AM

Originally posted by JeffJS

I see you are using the K20d. If it were the Kx or K7 I would suggest Live View but even then it can become cumbersome. Some get a split focusing screen to help with manual focus (center spot is split at 90 or 45 degree angle and when both parts are perfectly aligned, the subject is in focus). Where I would suggest you start, is practice with what you have. Start close, see what perfect focus looks like, and then zoom or move further back. Make sure that you've set the diopter on the viewfinder for maximum sharpness of the lines on the screen (that's the way I set mine).

For what it's worth, you Could try the live view on the K20d. I didn't find it all that useful, or even accurate when zoomed in. Your experience may prove different.

In your samples, the others are right. Your lady friend (wife?) at the furthest distance is somewhat dwarfed by the actual AF area of the camera. It's reasonable, that the camera might pick the nearest high contrast area for AF. You Could try selecting a different point and focus / recompose but I don't know if the AF area is different on the other points. I do know they are different Types of AF sensor points (line vs cross). That or try center AF and select something she is standing next to. At that distance, even the fence behind her (if she's leaning on it) would be good enough.

Frustrating I know, I sometimes experience the same thing with my DA12-24 but I'm confident it is not the camera or the lens. It's me and my expectations.

I looked at that KatzEye brand for the focus screens. I bet it would be a big help, but it's a bit pricey at the moment. I like those multipliers but I've read that it crops what' you're seeing - dunno if I would dig that.

In all this, I would have to agree- it's me and my expectations!

Originally posted by hangu

When using an under 40mm auto focus lens, it might be easier to focus on the foot/ground if the main subject is far away, especially if the ground is a grassy area with some contrast. The reason for this is that the area around the subject's foot is the largest area where distance is somewhat constant to your camera. With the long distance and wide focus length, the large depth of field should compensate just fine. It's not perfect but it's sure better than what you're pulling by focusing on the face. I usually focus on the torso/chest/crotch depending on which area is largest and has the most contrast.

I was JUST thinking about this. Instead of actually focusing on the person, try the ground at their feet.

I'll just push on and test things out at a basic level. I've adjusted the diopter, but maybe I'll do some tweaking some more. This has been some great help!

hangu · 07-08-2010, 09:29 AM

The Katzeye is a rip off but it works well. At the end of the day, $160 is not too expensive in the photography world.

Magnifiers do crop the corners a bit, but it mostly darkens it, which isn't a huge problem. If you're concerned, get a 1.22x magnifier instead of the usual 1.33x.

Marc Sabatella · 07-08-2010, 11:49 AM

Originally posted by imfinetoday

When you refer to focus sensor, are you speaking of the points in the viewfinder?

Well, the dots aren't literally the sensor, but yes, they are what is showing you the approximate location of the sensor relative to the image. The actual focus sensors are much larger than the red dots, though. So the camera is completely within in its rights if it decided to focus on something that is merely "near" the selected dot. That's why focusing on distant objects is tough. One trick is not to aim for the head, but the midriff, to present a larger target. Or finding something else even larger at the same distance to focus on. Even in the viewfinder, it should have been obviosu the camera had chosen to focus on the background in those last pictures.

And yes, manual focus takes practice, but it's certainly possible even without fancy aids.

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07-08-2010, 07:19 AM	#16
imfinetoday Junior Member Join Date: Jan 2010 Location: St. Louis, MO Posts: 43 Original Poster	Originally posted by Marc Sabatella In the distant shots, it's pretty clear the camera is simply choosing to focus somewhere other than on your subejct. No big surprise there, since the subject isn't big enough from that distance to cover the whole focus sensor. When you refer to focus sensor, are you speaking of the points in the viewfinder?

07-08-2010, 07:31 AM	#17
Parallax Senior Moderator Loyal Site Supporter Join Date: Apr 2008 Location: South Dakota Photos: Gallery Posts: 19,332	The points are not exact, and the actual focus area for any given point is quite a bit larger than the indicator light. It is possible, in the more distant shots, that even if you select the center point, and set it right on your subject's face it may still focus on the scenery in the background. This isn't a defect in the camera. It is a characteristic that you just need to learn to compensate for; either by using MF, or learning what else to focus on.

07-08-2010, 07:34 AM	#18
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Your posted sample shots look like a good opportunity to try Manual focus. AF is a tool, sometimes a great one, like all of the other features of your camera. However, sometimes it's better just to go back to basics.

07-08-2010, 07:52 AM	#19
imfinetoday Junior Member Join Date: Jan 2010 Location: St. Louis, MO Posts: 43 Original Poster	Originally posted by JeffJS Your posted sample shots look like a good opportunity to try Manual focus. AF is a tool, sometimes a great one, like all of the other features of your camera. However, sometimes it's better just to go back to basics. I've been thinking that. however, the times that i have tried manual, it's always come difficult for me. any helpful tips? is just something you have to take time to learn?

07-08-2010, 08:25 AM	#20
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	Originally posted by imfinetoday I've been thinking that. however, the times that i have tried manual, it's always come difficult for me. any helpful tips? is just something you have to take time to learn? I see you are using the K20d. If it were the Kx or K7 I would suggest Live View but even then it can become cumbersome. Some get a split focusing screen to help with manual focus (center spot is split at 90 or 45 degree angle and when both parts are perfectly aligned, the subject is in focus). Where I would suggest you start, is practice with what you have. Start close, see what perfect focus looks like, and then zoom or move further back. Make sure that you've set the diopter on the viewfinder for maximum sharpness of the lines on the screen (that's the way I set mine). For what it's worth, you Could try the live view on the K20d. I didn't find it all that useful, or even accurate when zoomed in. Your experience may prove different. In your samples, the others are right. Your lady friend (wife?) at the furthest distance is somewhat dwarfed by the actual AF area of the camera. It's reasonable, that the camera might pick the nearest high contrast area for AF. You Could try selecting a different point and focus / recompose but I don't know if the AF area is different on the other points. I do know they are different Types of AF sensor points (line vs cross). That or try center AF and select something she is standing next to. At that distance, even the fence behind her (if she's leaning on it) would be good enough. Frustrating I know, I sometimes experience the same thing with my DA12-24 but I'm confident it is not the camera or the lens. It's me and my expectations.

07-08-2010, 08:30 AM	#21
hangu Veteran Member Join Date: Feb 2010 Location: NYC Photos: Gallery Posts: 1,071	Every day, it seems, someone makes a post complaining about their camera/lens being front/back focused. The auto focus sensor is not human. It doesn't know if you're trying to shoot a portrait or if there just happens to be a bystander in the landscape you're trying to photograph. It does a decent job most of the time guessing which it is but it's not going to be right 100% of the time. That's just the nature of letting the camera do the work for you. Back/Front focus is ALWAYS present no matter what distance the subject is from your camera. It's more obvious when the subject is closer, not farther away. Focusing errors is usually very small. If your main subject is really blurry and the focus is way off, it's almost definitely because you didn't choose the correct camera setting. When using an under 40mm auto focus lens, it might be easier to focus on the foot/ground if the main subject is far away, especially if the ground is a grassy area with some contrast. The reason for this is that the area around the subject's foot is the largest area where distance is somewhat constant to your camera. With the long distance and wide focus length, the large depth of field should compensate just fine. It's not perfect but it's sure better than what you're pulling by focusing on the face. I usually focus on the torso/chest/crotch depending on which area is largest and has the most contrast.

07-08-2010, 08:47 AM	#22
imfinetoday Junior Member Join Date: Jan 2010 Location: St. Louis, MO Posts: 43 Original Poster	Originally posted by JeffJS I see you are using the K20d. If it were the Kx or K7 I would suggest Live View but even then it can become cumbersome. Some get a split focusing screen to help with manual focus (center spot is split at 90 or 45 degree angle and when both parts are perfectly aligned, the subject is in focus). Where I would suggest you start, is practice with what you have. Start close, see what perfect focus looks like, and then zoom or move further back. Make sure that you've set the diopter on the viewfinder for maximum sharpness of the lines on the screen (that's the way I set mine). For what it's worth, you Could try the live view on the K20d. I didn't find it all that useful, or even accurate when zoomed in. Your experience may prove different. In your samples, the others are right. Your lady friend (wife?) at the furthest distance is somewhat dwarfed by the actual AF area of the camera. It's reasonable, that the camera might pick the nearest high contrast area for AF. You Could try selecting a different point and focus / recompose but I don't know if the AF area is different on the other points. I do know they are different Types of AF sensor points (line vs cross). That or try center AF and select something she is standing next to. At that distance, even the fence behind her (if she's leaning on it) would be good enough. Frustrating I know, I sometimes experience the same thing with my DA12-24 but I'm confident it is not the camera or the lens. It's me and my expectations. I looked at that KatzEye brand for the focus screens. I bet it would be a big help, but it's a bit pricey at the moment. I like those multipliers but I've read that it crops what' you're seeing - dunno if I would dig that. In all this, I would have to agree- it's me and my expectations! Originally posted by hangu When using an under 40mm auto focus lens, it might be easier to focus on the foot/ground if the main subject is far away, especially if the ground is a grassy area with some contrast. The reason for this is that the area around the subject's foot is the largest area where distance is somewhat constant to your camera. With the long distance and wide focus length, the large depth of field should compensate just fine. It's not perfect but it's sure better than what you're pulling by focusing on the face. I usually focus on the torso/chest/crotch depending on which area is largest and has the most contrast. I was JUST thinking about this. Instead of actually focusing on the person, try the ground at their feet. I'll just push on and test things out at a basic level. I've adjusted the diopter, but maybe I'll do some tweaking some more. This has been some great help!

07-08-2010, 09:29 AM	#23
hangu Veteran Member Join Date: Feb 2010 Location: NYC Photos: Gallery Posts: 1,071	The Katzeye is a rip off but it works well. At the end of the day, $160 is not too expensive in the photography world. Magnifiers do crop the corners a bit, but it mostly darkens it, which isn't a huge problem. If you're concerned, get a 1.22x magnifier instead of the usual 1.33x.

07-08-2010, 11:49 AM	#24
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	Originally posted by imfinetoday When you refer to focus sensor, are you speaking of the points in the viewfinder? Well, the dots aren't literally the sensor, but yes, they are what is showing you the approximate location of the sensor relative to the image. The actual focus sensors are much larger than the red dots, though. So the camera is completely within in its rights if it decided to focus on something that is merely "near" the selected dot. That's why focusing on distant objects is tough. One trick is not to aim for the head, but the midriff, to present a larger target. Or finding something else even larger at the same distance to focus on. Even in the viewfinder, it should have been obviosu the camera had chosen to focus on the background in those last pictures. And yes, manual focus takes practice, but it's certainly possible even without fancy aids.