How can I improve focus?

vigilante

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One thing that plagues me are photos that appear ok in the viewfinder/LCD (even when I zoom in) but turn out to be quite a bit out of focus in post.
I tend to use the auto focus just about any time I'm not on the tripod, and almost always on spot focus.

My technique is to center the thing I want to focus on, press half-down to get the focus locked, then move to the frame I want and press down to shoot. I assume this is the correct technique for a center spot-focus shooting style?

In any case, we all know if you take a picture of a living thing, get the darn eyes in focus! But that's such a small area! If I can't get eyes in focus with spot, how else can I?

I thought, well maybe my lens sucks. It's nothing special, just the default Nikkor 18-55mm. My old camera is a D5100. But then yeah! I now have a D7100 also with the default Nikkor 18-55mm but a newer version with a locking button that locks the lens closed.

I seem to have the same problem getting good focus with the D7100 too!

Obviously this could be caused by other things like camera shake if my shutter speed is too slow, but I've toyed with that. When shooting objects, I can get a pretty focused shot with no camera shake at 1/60, but if my technique is sloppy, I like to be 1/100th or faster.

Anyway, I'm just stumped. Is this due to simply having the cheaper "comes with it" lenses? Or less than stellar cameras? Or do I need to use a different focus pattern or technique? Or do I just learn to manually focus as fast as possible? Is it because of where the zoom is? I try not to shoot at the outer extremes of the lens zoom.

Ideas?
 

weepete

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It's a common problem with the focus recompose method that it can throw your depth of field off at wide apertures, so keep the single point focus but either move the AF point or shoot wider and crop and see if that helps or try using a smaller aperture to get a deeper depth of field.
 

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My technique is to center the thing I want to focus on, press half-down to get the focus locked, then move to the frame I want and press down to shoot. I assume this is the correct technique for a center spot-focus shooting style?
You do this always? As weepete said, just selecting a different focus area would be the easiest method. If you move your shutter-button finger during the reframing, the focus might be going "off".

..if my technique is sloppy, I like to be 1/100th or faster.
That comment makes me think you're trying to keep the shutter speed slow for some reason. While an experienced photographer can hand-hold a slow shutter speed, it's usually only for low light conditions where you can't or don't want to use extra light. Is there some reason you don't increase the shutter speed?

That lens is acceptably sharp, so I would not blame it on the lens.

Since you've had the same issue with two different bodies, I'd say it is the lens or some cheap filter screwed on the front. Do some rigorous testing by mounting the camera to a tripod, increase the shutter speed, and keep your finger off it. Release the shutter by using the self-timer function.
 

table1349

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TTIWWP.gif


With exif data.
 

Derrel

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Center-AF-point-focus-then-recompose can lead to the WRONG focus distance at CLOSE distances and at wide f/stops. The longer the distanxce the subject is at, the more depth of field there is to cover focusing errors. Inside of 10 feet, the focus and recompose methoid can lead to a focus diustance error that might be greater than the depth of field the lens offers, so when the camera-to-subvject distance is short (close) it is best to move the focusing point using the camera's controller button, and to place the desired focus location actually OVER the eye of the person, or right oin the **exact spot** you want the focus to be at, focus with the AF square actually resting over the target, and then shoot!

If you set up the camera on a tripod, 10 feet from a wall,use three pieces of masking tape or three stick-on decals; place a decal where the left-most AF square hits the wall, then measure the distance to the outer focus square with a steel tape measure; then measure the distance to wall straight ahead, where the cenrter AF square covers the tape or decal, and then measure the far right focus square's distance; the two squares to the left and right will be **signiifcantly farther away** than the centrally-located AF square.

This will show you that at close distances, even relatively small things have an effect!

With a wide-angle lens, the edges of the frame that are in the picture can be verymvery FAR away! With a telewphoto lens like an 85mm f/1.8 lens, the picture angle (lens angle of view) will be narrow, and so the distances will be less-far away at the edges of the telephoto picture than they would be with a wide-angle lenbs like a 20mm lens!
 

jcdeboever

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Follow Derrel's advise on this. I had issues with a different lens and it confirmed the glass was back focusing on me, which did give me piece of mind. So his recommendation came in handy when I supposedly upgraded to a D7200. Everything was different from the D3300 and I was able to swiftly confirm it was the camera adding to my frustrations. I basically had one lens (35mm 1.8g) that was reasonably accurate. Solution? I traded it all in for Fujifilm system and haven't regretted it one bit. Nikon literally told me I had to calibrate each lens at each focal length (for zooms) and that was one of the advanced features of the D7200.... So I sent it in after uploading my focus test, they returned it and it was worse, now even the 35 was off. I raised the white flag and moved to a new system. So my point after the rant is, confirm for yourself that the hardware is working properly using Derrel's method before you go any further.
 

BananaRepublic

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Would pressing AEL lock work in this instance
 
OP
V

vigilante

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try using a smaller aperture to get a deeper depth of field.

True but if I shoot outside and use an auto mode, they typically like to close down the aperture anyway. I'll have to pay more attention to the settings and test some more.

You do this always? As weepete said, just selecting a different focus area would be the easiest method. If you move your shutter-button finger during the reframing, the focus might be going "off".

I never thought the reframing was an issue. In other words, I might only be panning over from center to 2/3rds or whatever. Focus center eyes then just pan over a little. It doesn't feel like the "distance" between lens and subject focus changes. But I guess I should try testing this.

That comment makes me think you're trying to keep the shutter speed slow for some reason.

No I just wanted to make a point that I am aware of potential shutter speed issues. The photos that trigger this thread were taken outdoors and since I was shooting a child, I just left the camera in auto mode so I could be quick.

TTIWWP.gif


With exif data.

Imagine a picture of a person............ they eyes aren't in focus well.... :p

Inside of 10 feet, the focus and recompose methoid can lead to a focus diustance error that might be greater than the depth of field the lens offers

I guess I'll have to run those tests and see how bad this could be. I was shooting in auto and just for fun in the back yard so I didn't even save NEF, just the JPGs.
That doesn't mean I haven't had this issue even when spending more time setting up manual settings and shooting highest quality.
 
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table1349

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try using a smaller aperture to get a deeper depth of field.

Wouldn't this actually make it harder to get my focus pin pointed? In other words, increases margin of error? It's just hard to tell if I'm focused right just through viewfinder.

You do this always? As weepete said, just selecting a different focus area would be the easiest method. If you move your shutter-button finger during the reframing, the focus might be going "off".

I never thought the reframing was an issue. In other words, I might only be panning over from center to 2/3rds or whatever. Focus center eyes then just pan over a little. It doesn't feel like the "distance" between lens and subject focus changes. But I guess I should try testing this.

That comment makes me think you're trying to keep the shutter speed slow for some reason.

No I just wanted to make a point that I am aware of potential shutter speed issues. The photos that trigger this thread were taken outdoors and since I was shooting a child, I just left the camera in auto mode so I could be quick.

TTIWWP.gif


With exif data.

Imagine a picture of a person............ they eyes aren't in focus well.... :p

Inside of 10 feet, the focus and recompose methoid can lead to a focus diustance error that might be greater than the depth of field the lens offers

I guess I'll have to run those tests and see how bad this could be. I was shooting in auto and just for fun in the back yard so I didn't even save NEF, just the JPGs.
That doesn't mean I haven't had this issue even when spending more time setting up manual settings and shooting highest quality.
Hi mister mechanic, my car doesn't run right, but I don't have time to bring it to you to look at. What's wrong with it and how can I fix it.

Answer: Pay for Auto Shop Classes.
 

Designer

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Obviously, in order to properly address your issue, we're going to need more information. If you can help us out with that information, then things will go smoother and quicker.
 

Murray Bloom

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If you set up the camera on a tripod, 10 feet from a wall,use three pieces of masking tape or three stick-on decals; place a decal where the left-most AF square hits the wall, then measure the distance to the outer focus square with a steel tape measure; then measure the distance to wall straight ahead, where the cenrter AF square covers the tape or decal, and then measure the far right focus square's distance; the two squares to the left and right will be **signiifcantly farther away** than the centrally-located AF square.

This will show you that at close distances, even relatively small things have an effect!

Hey, Derrel. I almost always agree with your analyses, but this time, I think you've set up a straw man. What you describe is a straightforward implementation of the Pythagorean Theorem. However, in this case, I don't believe it applies; or at least, not entirely.

When Vigilante turns the camera to bring his central focus point to the desired focus area, the PT goes out the window, since his AF system is still measuring/retaining the actual distance to the subject. Then when he recomposes, in theory, the lens remains focused at that distance. To use your example, the focused distance would actually be beyond the central piece of tape, as you suggest.

This is a confusing situation, which I surmise may have more to do with curvature of field. In theory, at any given focal distance, the area of sharpness would resemble a semi-sphere in front of the lens, and the sharpest part of the projected image in the camera would also be spherical (just a lot smaller). However, the focal plane (sensor or film) is flat, causing what should be sharp focus to fall in front of or behind the sensor in many areas.

The best copy and macro lenses correct for this very well, but I seriously doubt that kit zooms do nearly as good a job of it. I surmise that the "focal sphere" in front of the lens is at least somewhat flattened due to the flatness of the sensor. Therefore, the 'press and hold' prefocus method would be less than optimal, especially at relatively large apertures, and at larger offsets from dead center; partly for the reasons you mention.

Assuming that the issue is lens-related (since Vigilante experienced it with two different camera bodies), the fix would be, as you suggest, to move the primary focus point to the subject, using the multi-function control on the rear of the camera. This is a lot more tedious than simply turning the camera, but stands a lot better chance of achieving the desired result.
 
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Dave442

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Generally the auto-focus with focus and recompose gives me better results than trying to manual focus. Have you compared focus when doing a focus and recompose and just staying focused on the point and not recomposing? Have you tried faster shutter speeds like 1/500 and stopping the lens down a stop?

In Derrell's example at 10' and 50mm focal length on your camera if we just consider horizontal movement the 10' to center would be 10.27' to the very edge of the frame and just 10.07' if your subjects eye is now over at the rule of thirds gridline after you recomposed. So you focused at 10.07' and then took the picture after recomposing with the subject now at 10' away from the plane of focus.

If you know that you plan to zoom in to 100% on the eye in the computer then you probably want to account for that extra distance, if you don't have a main focus point like an eye in the frame then you are probably good with the focus and recompose.

At f/5.6 you have about 1.5' DOF to the rear of the focus point so overall the image should look good at normal viewing distance - if you printed out the image to just over 4.5' wide the persons face would be about life size and if you stood about a foot away looking at the eye then it probably will not look tack sharp, but if you are 3 or 4 feet away it should start to look decent. This is considering the lens/body is focusing correctly and everything else is good with the image.

Of course, if you go buy a better lens and start shooting at f/2.8 or f/1.4 then you are going to have even more problems with focus as you will have much less depth of field.
 

astroNikon

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One thing that plagues me are photos that appear ok in the viewfinder/LCD (even when I zoom in) but turn out to be quite a bit out of focus in post.
I tend to use the auto focus just about any time I'm not on the tripod, and almost always on spot focus.

My technique is to center the thing I want to focus on, press half-down to get the focus locked, then move to the frame I want and press down to shoot. I assume this is the correct technique for a center spot-focus shooting style?

In any case, we all know if you take a picture of a living thing, get the darn eyes in focus! But that's such a small area! If I can't get eyes in focus with spot, how else can I?

I thought, well maybe my lens sucks. It's nothing special, just the default Nikkor 18-55mm. My old camera is a D5100. But then yeah! I now have a D7100 also with the default Nikkor 18-55mm but a newer version with a locking button that locks the lens closed.

I seem to have the same problem getting good focus with the D7100 too!

Obviously this could be caused by other things like camera shake if my shutter speed is too slow, but I've toyed with that. When shooting objects, I can get a pretty focused shot with no camera shake at 1/60, but if my technique is sloppy, I like to be 1/100th or faster.

Anyway, I'm just stumped. Is this due to simply having the cheaper "comes with it" lenses? Or less than stellar cameras? Or do I need to use a different focus pattern or technique? Or do I just learn to manually focus as fast as possible? Is it because of where the zoom is? I try not to shoot at the outer extremes of the lens zoom.

Ideas?
I don't know if anyone mentioned this, but why not just move the "center spot" focus point to the side if you are using a single focus point instead of just in the middle ?

Also you mentioned the slow shutter speeds. Do you know if your technique is "sloppy" or not before or after shooting? Why not just, to eliminate it entirely from the potential problem list, raise your shutter speed above what you think is minimum and to something like 1/125 or ever 1/250?

Or better yet since it is on a fixed non-moving subject, use a Tripod and remote shutter release as a test. Or just test your technique on other objects in a fixed repeatable setup to check your technique. With digital cameras it costs nothing to set up a similar scenario in a backyard or something. Then test this until it gets acceptable results, over and over.
 

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