Focus problem

[brmill26]

This afternoon / evening was my first attempt at taking true landscapes with my XTi and 50mm f1.8 II lens. I took about 160 shots. I discovered that nearly all of my shots with a wide aperture (roughly, less than 3.5) were anywhere from noticeably off focus to completely wrong focus.

Camera shake was not the issue, as every shot in question had a shutter speed of at least 1/100, and most 1/400 or higher. I was shooting in Aperture priority mode, standard picture style, center focus point selected for the AF.

Is this a technical problem or a photographer problem? Thanks for your help.

This shot was one of the worst - taken at f1.8, 1/200, partial metering, ISO 100. The trees weren't the problem either - there were shots taken from clear spots with the same issue.

[livin4lax09]

you should be able to notice if the shot is out of focus when you are looking through the viewfinder. If the shot looks sharp through the viewfinder and it coems out blurry, you should adjust your diopter on the back eye piece. It might be an AF error in the camera or lens, but did these look in focus when you took them?

[drg]

For the greatest Depth of Field you want a smaller aperture (bigger number). Usually f8-f16 and certainly with that lens you will get great results!

This way the majority of the image will be in focus from front to back. There are lots of techniques and suggestions, but start with f8 or greater!

Best wishes !

[Frog]

What was your focus point?
I think there is so much depth in the shot, that there is one point in focus but the rest not due to the large aperture.
Appears as though the tree limbs have the better focus. Was it windy?

[Grandpaw]

My guess is that you did not set the Fstop to the largest number on the lens after placing it on the camera and also you need to slide the lock switch on the lens to the lock position to keep it from changing, Jeff

[brmill26]

livin4lax09 - I have the diopter adjusted for my glasses, but no I could not tell on these shots that it was out of focus. The viewfinder is so small and the distance of the shot is so great I really couldn't tell.

drg - thanks, I shot some of my earlier shots (in brighter light) stopped down. I was using the wider aperture here both b/c of the darker light (I was hand-holding) and because I wanted to put the tree limbs out of focus. When I got the tripod out later I went back to the higher apertures and they were fine.

frog - focus point was on the blue/grey skyscraper. It was dead calm. That crop doesn't shot it, but even the tree branches nearest me are well out of focus. That's why I'm baffled... nothing anywhere in the shot was in focus.

Grandpaw - the lens is fully electronically-controlled, there's no aperture control on the lens, nor any slidelock. The only switch is for AF/MF, and it was always on AF.


Thanks for all the quick responses guys. I still have no idea what the problem is... there are a FEW open-aperture shots that came out, but 95-98% of them were just like this one. Is it possible that the AF misses the focus that much? Does distance affect its performance? I don't have hardly that error rate on closer shots.

[brmill26]

Here's another example - I've cropped this one on the side so you can see, nothing's in focus near or far.

Shot taken in Av mode, f3.2, 1/400, ISO 100, no wind. The second shot/crop is in focus, taken Av mode, f3.5, 1/640, ISO 100.

[mwfanelli2]

It looks like two problems to me:

1. The biggest problem is that you are shooting with f/1.8 as the aperture. At f/1.8 there is very little depth of field. In effect, you are focusing at a tiny area and everything else is out of focus.

2. You say the shutter speed is at least 1/100 s but the EXIF data in your first image shows something much, much slower than that. The image itself supports the EXIF data. Either the EXIF is wrong or you didn't have the shutter speed set where you thought. You can't handhold a 50mm lens at anything slower than about 1/50 of a second.

Put the camera on a tripod, set the aperture to f/8 in aperture priority mode and see what you get.

[SmartWombat]

My biggest problem is knocking the switches on the 70-200 or 24-70 as I drag the lens out of the bag.

Check that the lens is functioning in AF mode, not MF.
You'll see, hear, and feel it working even on a heavy 1D body because the 1.8 isn't the quietest lens ...

[another view]

I have the diopter adjusted for my glasses, but no I could not tell on these shots that it was out of focus. The viewfinder is so small and the distance of the shot is so great I really couldn't tell.

Just to be sure - if you're looking thru your glasses the diopter should be at zero. If you take your glasses off, then you'll need a correction from the diopter. Viewfinder size is one reason I usually wear contacts when shooting.

There is a chance that even a 1/100 shutter speed with a 50mm lens could have some camera shake to it. You'd have to almost try to do it by the time you got to 1/400, but it is possible. With a wide aperture (f1.8 or even f4) you'll have a shallow depth of field so that objects closer and farther in the focus point won't be in focus, but of course something should be. Handholding a camera is a bit of a variable, and the tripod that Michael recommended would take that variable out of the equation. It's an essential thing to have for serious photography, so you might want to put one on the list. Check other threads here (one fairly recent) for some recommendations.

AF works by detecting contrast and I wonder if it didn't "see" a building too easily because it's a big flat surface. It may have seen the edge of the building a little more easily. Just a guess...

[freygr]

I shoot with eye glasses on, and mainly rely on the auto focus. The other problem is the setting in the menu for auto focus. With the lack of DOF with a wide open 50mm an area mode auto focus setting will not give you good results for landscape photography. Unless I need flash the camera lives in aperture priority mode, and auto ISO is always turned off.

[mn shutterbug]

It looks like two problems to me:

1. The biggest problem is that you are shooting with f/1.8 as the aperture. At f/1.8 there is very little depth of field. In effect, you are focusing at a tiny area and everything else is out of focus.

2. You say the shutter speed is at least 1/100 s but the EXIF data in your first image shows something much, much slower than that. The image itself supports the EXIF data. Either the EXIF is wrong or you didn't have the shutter speed set where you thought. You can't handhold a 50mm lens at anything slower than about 1/50 of a second.

Put the camera on a tripod, set the aperture to f/8 in aperture priority mode and see what you get.

When I check the exif on the first photo, it matches what he posted - 1/200 sec. But yeah, 1.8 sure won't give you much of a dof.

[Xia_Ke]

HI br, CLICK HERE for an article that I think you might find useful

[brmill26]

mwfanelli2 - All of my data (file, ZoomBrowser, and camera) show 1/200 for the first image. I suppose it would be possible to have shake at that speed, but my hands aren't that bad.

Thank you so much, everyone, for all of your responses. In looking at all of my images, which I was taking at many various apertures (still getting used to this stuff, seeing what the different looks were), and my results look exactly like the link Xia Ke posted. Some apertures were very soft, yet others were very sharp, with no obvious explanation - except that article provides it perfectly.

I guess I'll just go back through and see which apertures were sharp and make note of those for landscape use. I was seeing all those blurred, foggy looking images and thinking, what the heck is wrong with this thing. Now it makes sense.

As for the tripod, I have one, I just wasn't using it for several of those shots b/c I was in a bit of a hurry (stupid, yes), but I did break it out later. It's not quite perfectly tack-sharp, but it's definitely better. This one was f/8, 2sec, ISO 100.

Thank you all, again, you guys are great and a huge help. :thumbsup:

[Frog]

Yup! That's a big diff.
Your question probably answered not only yours but many others that have read this thread.

[another view]

I guess I'll just go back through and see which apertures were sharp and make note of those for landscape use. I was seeing all those blurred, foggy looking images and thinking, what the heck is wrong with this thing. Now it makes sense.

As for the tripod, I have one, I just wasn't using it for several of those shots b/c I was in a bit of a hurry (stupid, yes), but I did break it out later. It's not quite perfectly tack-sharp, but it's definitely better. This one was f/8, 2sec, ISO 100.

A 50mm f1.8 lens should be very, very sharp. Unless there's a serious problem with the lens or the camera, whatever the lens is focused on will be sharp (assuming no camera shake, etc). For example if you focused the lens at 10' and shot wide open, anything closer than about 8-9', or farther than about 11-12' would be out of focus - and the farther it was from 10', the more out of focus it would be. With a smaller aperture (higher "f" number), you'll have more in focus closer and farther from the focus point. It's all in what results you're looking for; smaller apertures aren't necessarily better, etc.

Another thing that helps with long exposures on a tripod is using a remote release or the self timer. This avoids a little camera shake as you press the button. I have my self timer set at two seconds so I'm not actually touching the camera when I shoot, but don't have to wait for a long time. If timing is critical, it's best to use a remote release. But this shot looks much better!

[freygr]

clip...
As for the tripod, I have one, I just wasn't using it for several of those shots b/c I was in a bit of a hurry (stupid, yes), but I did break it out later. It's not quite perfectly tack-sharp, but it's definitely better. This one was f/8, 2sec, ISO 100.

Just remember if the tripod moves you will have problems getting the images sharp also, most of the time in most stores the sales personal just don't know what a good tripod can add a the photograph (sharpen it up allot).

[Greg McCary]

I find my pictures are a little sharper if I focus one third of the way into the shot instead of just focusing to infinity. Hyperfocal Focus.The technique works for me.
http://www.vividlight.com/articles/2314.htm

[Jimmy B]

BRMill use your tripod, manual focus, set your camera for a 2 second delay, press the shutter button very gently and the picture will take it self.
The 50 F 1.8 doesn't have a focus scale so manually focus it before the shot.
My .02 cents
Jimmy B

[brmill26]

A remote release is definitely on my wanted list... until then, I can deal with using the self-timer (as I did for the night shot above).

Mainly the point I've learned most over the past couple days is how much a tripod helps sharpen up the images. I guess, not being used to such high resolution, I never really noticed how big a difference it can make. But with the XTi, I've noticed it makes a big difference on a lot of shots.

Greg - thanks for the tip on Hyperfocal, I'll have to try that out next time.

Jimmy - I've tried manually focusing a few times, but I'm almost always just a bit off. It seems like there's quite a lot of change for very little movement on the focus ring, so I have a hard time zeroing in on the precise spot.

[another view]

Mainly the point I've learned most over the past couple days is how much a tripod helps sharpen up the images. I guess, not being used to such high resolution, I never really noticed how big a difference it can make. But with the XTi, I've noticed it makes a big difference on a lot of shots.

No doubt that it does, but if you were handholding a camera with a 50mm lens at 1/100 or faster you'd almost have to try to get enough camera shake to cause that much blur. I think this may have been part of the problem, but only part of it (and probably a small part). Even at a fairly wide aperture, a 50mm lens focused on something a long ways in the distance will have a bit of depth of field to it. The buildings should have been sharp but the tree branches in the foreground wouldn't be.

Don't trust turning the focusing ring all the way until it stops to be sharp at infinity - this isn't always the case but usually more of a problem with telephoto lenses (actually not a problem, but a long story). With autofocus and non-moving subjects, a lot of times it's easiest to find something to focus on, lock the focus (usually by holding the shutter release down halfway) and then re-compose and shoot.