Newbei bought a 35mm without VR

[Josh66]

Your lens may be back-focusing. On the second set, the Christmas lights box looks sharper the the box with the bar code that you focused on... The shadows show that the bar code was sticking out in front of the other box a little... (Maybe 1/2 inch?)

Take a 100% crop from picture #3 right where it says "C9" and compare that to the 100% crop of just the bar code...

 

[MTVision]

I can't use manual better than auto focus. Here is my pics.

#1 1/4000s, f4, iso400, AF-A spot metering

[/URL] DSC_0031 by RichardsFlik, on Flickr[/IMG]

#2 crop

[/URL] DSC_0031_01 by RichardsFlik, on Flickr[/IMG]

#3 1/100s, f4, iso200, AF-S spot metering

[/URL] DSC_0040 by RichardsFlik, on Flickr[/IMG]

#4 crop

[/URL] DSC_0040_01 by RichardsFlik, on Flickr[/IMG]

When I use AF-S, the shutter is twice as fast as AF-A.

I don't believe Af-s would increase your shutter speed. Do me a favor and Set your aperture to the lowest f-stop (f11 maybe) and adjust the shutter speed until you see a correct exposure. Take a picture of that.

 

[Josh66]

F/11 may not be best for focus testing... I would do this sort of thing wide open just to make any changes very clear...

edit
If only the focus mode is changing, exposure settings should not change. Do tests like this in manual so nothing changes.

 

[MTVision]

Your lens may be back-focusing. On the second set, the Christmas lights box looks sharper the the box with the bar code that you focused on... The shadows show that the bar code was sticking out in front of the other box a little... (Maybe 1/2 inch?)

Take a 100% crop from picture #3 right where it says "C9" and compare that to the 100% crop of just the bar code...

What is back focusing?

 

[MTVision]

F/11 may not be best for focus testing... I would do this sort of thing wide open just to make any changes very clear...

edit
If only the focus mode is changing, exposure settings should not change. Do tests like this in manual so nothing changes.

I figured it was a DOF issue since he was shooting 6ft away.

EDIT: Earlier in the thread OP said 3ft it focused fine but not at 6ft.

 

[Josh66]

Your lens may be back-focusing. On the second set, the Christmas lights box looks sharper the the box with the bar code that you focused on... The shadows show that the bar code was sticking out in front of the other box a little... (Maybe 1/2 inch?)

Take a 100% crop from picture #3 right where it says "C9" and compare that to the 100% crop of just the bar code...

What is back focusing?

Focusing behind the intended point of focus.

 

[MTVision]

Your lens may be back-focusing. On the second set, the Christmas lights box looks sharper the the box with the bar code that you focused on... The shadows show that the bar code was sticking out in front of the other box a little... (Maybe 1/2 inch?)

Take a 100% crop from picture #3 right where it says "C9" and compare that to the 100% crop of just the bar code...

What is back focusing?

Focusing behind the intended point of focus.

Originally Posted by RichardsTPF
I have no problem to shoot bar code from 3ft away. But at 6ft, the image become blur.
While the camera mount on the tripod 6' away from the box, looking at the barcode in the view finder, shaking my camera (no tripod leg movement), I can see the bar code circle around inside the center focus point. Do you think this little bit space/range of shaking could cause the blur?
Here are couple more pics shot at SP mode on the tripod. #1,2 are 3ft away from the subject, and #3,4 are 6ft away from subject."

Would it back focus just based on distance??

 

[Josh66]

Do you have a ruler or something? Shoot that at a 45 degree angle, and pay close attention to where you focus.

On this shot, I focused right where the 200mm line is. I placed the scissor tip there to remind myself in case I forgot.


08031111 by J E, on Flickr

To me, the 205mm line looks sharper than the 200mm line... So, it looks like my lens is back-focusing by 5mm... (Probably more like 3mm, judging by the smaller lines.)

 

[Josh66]

Would it back focus just based on distance??

No, but more distance will make the effects less noticeable.

It could be possible that it's only off a little, and it's only noticeable at close distances.

 

[MTVision]

Would it back focus just based on distance??

No, but more distance will make the effects less noticeable.

It could be possible that it's only off a little, and it's only noticeable at close distances.

Yeah but the OP said at 3 feet it was clear and only at 6 feet was it blurry. So, if it was backfocusing wouldn't you think it would be blurry at 3ft not at 6ft?

EDIT: Sorry I'm asking a million questions! I'm curious.

 

[RichardsTPF]

I don't believe Af-s would increase your shutter speed.

I was wrong. sorry.

 

[Josh66]

Would it back focus just based on distance??

No, but more distance will make the effects less noticeable.

It could be possible that it's only off a little, and it's only noticeable at close distances.

Yeah but the OP said at 3 feet it was clear and only at 6 feet was it blurry. So, if it was backfocusing wouldn't you think it would be blurry at 3ft not at 6ft?

EDIT: Sorry I'm asking a million questions! I'm curious.

You're right. I didn't catch that before.

If it's off, it will get worse the closer you get. (well, it won't "get worse", but it will be more obvious.)

...Most likely missed focus, like everyone else said.

 

[MTVision]

No, but more distance will make the effects less noticeable.

It could be possible that it's only off a little, and it's only noticeable at close distances.

Yeah but the OP said at 3 feet it was clear and only at 6 feet was it blurry. So, if it was backfocusing wouldn't you think it would be blurry at 3ft not at 6ft?

EDIT: Sorry I'm asking a million questions! I'm curious.

You're right. I didn't catch that before.

If it's off, it will get worse the closer you get. (well, it won't "get worse", but it will be more obvious.)

...Most likely missed focus, like everyone else said.

Do you think it could be DOF?

 

[RichardsTPF]

Sorry I'm asking a million questions! I'm curious

This my first time heard about back focus. I have million questions too.

Do you have a ruler or something? Shoot that at a 45 degree angle, and pay close attention to where you focus.

shall I use f1.8? That gives shortest DOF.

And here is the 100% crop (If I am right, I zoom in to 100%, then crop the pic.)

[/URL] DSC_0040_02 by RichardsFlik, on Flickr[/IMG]

[/URL] DSC_0040_03 by RichardsFlik, on Flickr[/IMG]

 

[Josh66]

Sorry I'm asking a million questions! I'm curious

This my first time heard about back focus. I have million questions too.

Do you have a ruler or something? Shoot that at a 45 degree angle, and pay close attention to where you focus.

shall I use f1.8? That gives shortest DOF.

And here is the 100% crop (If I am right, I zoom in to 100%, then crop the pic.)

[/URL] DSC_0040_02 by RichardsFlik, on Flickr[/IMG]

[/URL] DSC_0040_03 by RichardsFlik, on Flickr[/IMG]

Yes, that's right - zoom in to 100% then crop. Just as I suspected, the box that was farther away looks sharper...

When I do tests like this, I do them at the widest aperture the lens can do (2.8 in my example above) just so the DOF will be the smallest and any errors will be more obvious.

EDIT
Also, move the subject to the correct focus point. Try not to move the camera at all... (For the testing...)