people focus issues

magicpic

again could someone look at this shot, Canon rebelxt, f4.0, ISO 100, lens 70-300(FL 75mm), SS 1/320, AP, spot metered (one shot) one focual point....thanks..janis

Andy

Other thread, similar issues (for background, this will help those who may be able to help you).
http://www.dgrin.com/showthread.php?t=50696

Are you focusing and recomposing?
Where, exactly, was the one focus point set on?

magicpic

Andy wrote:

Other thread, similar issues (for background, this will help those who may be able to help you).
http://www.dgrin.com/showthread.php?t=50696

Are you focusing and recomposing?
Where, exactly, was the one focus point set on?

One focus point was on her eyes and I did recompose on this one..janis

gpphotos

it looks like the autofocus on the rebel locked onto her shoulder. if you want to get all of her in focus, then try moving to about f/11 and make other adjustments to your settings are necessary...or just make sure the autofocus locks onto her face.

this pic also looks a bit underexposed for my tastes.

if i were shooting this shot i'd go with iso 200 with those settings, that would probably fix the exposure.

Andy

magicpic wrote:

I did recompose on this one..janis

http://www.dgrin.com/showthread.php?t=5642

Seneca

Looks like the focus was on her arm.

jsedlak

The only commonality between the pictures that I can see is that the focus seems to be just in front of where it was intended. This is just a shot in the dark, but I would just do some simple tests to see if the lens/camera front focuses.

Andy

Guys, it's not a lens issue.

She focused and recomposed, that's the fault here, plain and simple...

gavin

Andy wrote:

Guys, it's not a lens issue.

She focused and recomposed, that's the fault here, plain and simple...

What wrong with focusing and recomposing? if you focus on the eyes, and the focus is locked... how does recomposing do anything?

Shane422

Just to summarize the threads that Andy has pointed out here. Focus lock locks the focus at a distance, then recomposing can change the distance from the original subject to the lens. In the case of a wide aperature (i.e. shallow DOF), this can be problematic and create an OOF situation. Its best to focus with one of the other focus points available and avoid recomposing.

LuckyBob

gavin wrote:

What wrong with focusing and recomposing? if you focus on the eyes, and the focus is locked... how does recomposing do anything?

Shane422 wrote:

Focus lock locks the focus at a distance, then recomposing can change the distance from the original subject to the lens.

Not to mention that recomposing by tilting the camera changes the focal plane itself, so if you focus on the eyes and recompose elsewhere by tilting the camera (even if you can magically stand perfectly still along with your model), the eyes won't be in the focal plane anymore.

http://www.dgrin.com/showthread.php?t=5642

Andy

gavin wrote:

What wrong with focusing and recomposing? if you focus on the eyes, and the focus is locked... how does recomposing do anything?

Right. But she didn't

Focus and recompose in the right hands, with the right understanding, can be fine. Just be careful out there, folks

pathfinder

Janis,

Are you ABSOLUTELY positive that you did not half release your shutter after achieving focus lock and let the camera refocus on her shoulder??

The AF in the Rebel XT, like the 10D and the 20D, STRONGLY favors straight lines, with high contrast, over soft organic forms, and I suspect that is what happened here. Facial contours do not have sharp clear precise borders that AF likes to grab, unless you are very precise in picking and placing the AF points. The AF systems in the Rebel and the 20D also strongly favor the closer points over the more distant points, as in this case. The light was soft and rather dim also, wasn't it??

Focus-Recompose was done by all of us, years ago, with center only AF points, or earlier with split image rangefinder reticles in the ground glass. But Canon is quite clear, that you are better off using the proper AF point and NOT recomposing as Jonathon Wienke discusses so well in his article

Focus-Recompose tends to make the focal point behind the desired focus plane, not in front of it, which is why I suspect the camera refocused on her shoulder.

I find the Rebel, 20D, 30D needs a very firm hand using the AF points - I use ONLY 1 AF point which I choose - I do not allow the camera software/firmware to choose an AF point because invariably it will choose the wrong one.

Focus Recompose is not a significant concern at distances greater than 20 or 30 feet. But in the 4 - 8 feet range it can introduce focus inaccuracies, but not to the extent that I see here. I think the camera refocused before exposure.

You might try setting up a target and checking the focus on a target also.

If you are certain that you did not let up on the shutter to release focus lock, then I am all wet of course. :hide :giggle

But my images are usually sharply focuse

LiquidAir

Shane422 wrote:

Just to summarize the threads that Andy has pointed out here. Focus lock locks the focus at a distance, then recomposing can change the distance from the original subject to the lens. In the case of a wide aperature (i.e. shallow DOF), this can be problematic and create an OOF situation. Its best to focus with one of the other focus points available and avoid recomposing.

This problem only shows up when you are quite close to the subject at wide apetures. Assuming proper execution at f/4 on an APS-C camera won't see significant focus and recompose errors when you are further than about 2 feet from the subject. With a 70mm lens that shot was probably taken from about 6 feet away so I don't think that is the issue in this case.

If you are shooting a portrait like this one on an APS-C body you should worry if you are using a 50mm (or wider) lens with the apeture wider than f/2. By the time you stop down to f/2 any focus and recompose errors will only be visible on very large prints. On a full frame body (like the 5D) the problem is more severe. If you frame this same shot at 50mm on a 5D, you should stop down to f/4 if you want to focus and recompose. With an 85mm lens on a 5D you have a bit more latitude and can focus and recompose fairly reliably at f/2.8.

As for the article by Jonathon Wienke: I have done a lot of real world testing on focus and recompose and focus points with my 5D. When the apeture is wider than f/4 I get quite dramatically better focus on my 5D using the center point to focus and recompose than I do with the off center points. When I get into the regime where focus and recompose fails I shift to manual focus. Personally, I will only use the off center points on moving subjects and even then I will stop down as much as possible. If I had a 1-series body I am sure I would use the off center points, but on the 5D cameras I find them next to useless.

Getting sharp focus on people with fast lenses is quite difficult and requires a lot of practice and there are some tricks to the trade. Here are a couple I use:

1. I aim the AF point slightly below the eye. Sometimes when the AF point is directly on the eye it picks up the eyebrow instead which results in front focusing slightly. Lowering the AF point a bit gives me more reliable focus on the eye.

2. When using focus and recompose in a situation where I really shouldn't I will deliberately front focus the camera a tad so when I recompose the plane will be in the right place. The eyebrow, hairline or the tip of the nose are good places to pick up a slight front focus.

El Kiwi

LiquidAir wrote:

Here are a couple I use:

1. I aim the AF point slightly below the eye. Sometimes when the AF point is directly on the eye it picks up the eyebrow instead which results in front focusing slightly. Lowering the AF point a bit gives me more reliable focus on the eye.

2. When using focus and recompose in a situation where I really shouldn't I will deliberately front focus the camera a tad so when I recompose the plane will be in the right place. The eyebrow, hairline or the tip of the nose are good places to pick up a slight front focus.

Thanks for the tips - I must try these.

magicpic

focus point
When photogaphing people is it best to use the center focus point and recompose or depending on the subjest us the focus point that is the close.........hope to hear...widget

magicpic

Shane422 wrote:

Just to summarize the threads that Andy has pointed out here. Focus lock locks the focus at a distance, then recomposing can change the distance from the original subject to the lens. In the case of a wide aperature (i.e. shallow DOF), this can be problematic and create an OOF situation. Its best to focus with one of the other focus points available and avoid recomposing.

I really do think that my problem has been the center focus point and them the recompose situation....to use the center focus and recompose what can you distance and DOF be...and what is OOF? hope to hear...my camera is in the shop so when it gets out I can not wait to try the different foucs points to see if the sharpness is there.........widget

System

I almost exclusively use the center focus point and then recompose-

I guess this is pretty common on cameras but I only use canon-

I'll put the center point on the eye, push the shutter button halfway down, hold it there as I recompose, then take the pic-

if you let up on the shutter button as you recompose, you end up refocusing and then the face most of the time will be oof (out of focus)-

if I'm concerned about the exposure (usually shutter speed as I'm usually using aperture priority), I'll lock it with the button that's at my thumb, as I recompose-

I need to learn to deal with the other focal points, but then there's a lot of things I need to deal with-

hope that helps-