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Very soft image - Canon 50mm, 1.4, USM

qqqavi
Contributor

Hi everyone, 

 

I own a Canon 50mm 1.4, USM lens and even though I already knew the image was a little bit soft at aperture like 1.4, 1.8 , in a recent test the image actually look terrible. I don't know if this is normal or it is because the lens is damaged.

 

I attached you an example at f1.8.

 

_MG_8088.JPG

 

At f2.5 looks a little better, still with a lot of fringe on edges. 

 

_MG_8089.JPG

 

Thank you. 

8 REPLIES 8

kvbarkley
VIP

Assuming that this is a crop frame camera, and that the subject is .3 M away from the camera, A DOF calculator shows that the acceptable depth of field ranges from .299 to .301 m, so very little of the subject will be sharp even under ideal conditions.

 

Questions:

What were you focusing on?

Is this on a tripod?

 

If you were handholding, did you keep the camera from shifting back and forth less than 2mm? I doubt it. I would guess that you were handholding and the camera shifted slightly back so that none of the subject is in focus.

1. If you look closely at the first image you'll notice that that look like an optical issue (looks like smearing) not shallow depth of field, nor motion blur.

2. I was focusing on the center of the ball and I was 1 m away.

3. if again look closely at the first image, you'll notice that it doesn't really matter what area I was focusing on since the entire image is smeared (not out of focus), more noticeable at the edges. 

4. At f1.8, f2.0, f2.5 I've never achieved a sharp image. I have also tested it by using the lens set to manual focus in video mode. Trust me, it's impossible to get the ball in focus at 1 or 2m away. 

5. I can get an acceptable sharp image at f4

 

Thank you. 

 

 

 

 

 

 

 

 

 

 

 

What camera?

 

Are you handheld?

 

If you can't focus with a tripod and liveview there is something wrong with the lens.

qqqavi
Contributor
Tripod, liveview, canon 7d

diverhank
Authority

There are two things I'd try before declaring there's something wrong with the lens, if I were you.  I'd use a tripod for all tests to eliminate user's error.

 

1. Manual focus, using live view @ 10X magnification.  I find that in low light the Auto-focus is lacking and that may not be the lens fault.

 

2. Try it outdoors where the light is good, with AF and MF.

 

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Diverhank's photos on Flickr

qqqavi
Contributor
The camera was mounted on a tripod, shutter 1/200 in daylight conditions. I tried both manual and automatic focus in liveview at 10x. The more I look at the pictures the more I believe that is an optical issue since there was no motion blur and that look like smearing, not out of focus.


@qqqavi wrote:
The camera was mounted on a tripod, shutter 1/200 in daylight conditions. I tried both manual and automatic focus in liveview at 10x. The more I look at the pictures the more I believe that is an optical issue since there was no motion blur and that look like smearing, not out of focus.

In that case, there is indeed something wrong with this.  Mine doesn't do this, even at f/1.4.

================================================
Diverhank's photos on Flickr

Let me ask two more questions.

First are you perpendicular to the ball?  If you are at an angle the DOF can be worse.

Second how big of a crop is the example?

EB
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