18-250

[elty12345]

It doesn't look very sharp to me, is it normal? (100% center crop)

F8 100mm



F8 250mm

 

[Koolpep]

did you use a tripod and/or SSS?

Or was it shot handheld? At which speed?

--

 

[glarry]

No, it isn't normal, your lens has a back focus problem(if you did take correct the photo- center focusing).

 

[TCav]

I think what you're seeing is more chromatic aberration than a lack of sharpness.

 

[Ed at Ridersite]

Looks like a focus issue to me. The text on the right side in #1 looks pretty sharp. Less sharp in #2, but still sharper than the center. I would expect it to be a little less sharp at 250mm. Still, the text on the right looks acceptable in both. If you post process, that level of sharpness can look pretty nice.
--
AEH
http://aehass.zenfolio.com/
Question: What do you do all week?
Answer: Mon to Fri. Nothing, Sat & Sun I rest!

 

[05_GD7]

To echo Koolpep, this test is meaning less without knowing:

• Tripod or handheld?
• SSS on or off?
• Shutter speeds?

 

[TCav]

To echo Koolpep, this test is meaning less without knowing:

• Tripod or handheld?
• SSS on or off?
• Shutter speeds?

What 05_GD7 is looking for is an indication that what we're seeing may be motion blur. Motion blur is when the camera shakes during an exposure, and is more likely to occur during long exposures, or when the camera is handheld and SuperSteadyShot is off.

I don't think what we're seeing is motion blur. Motion blur is directional. It shows a blur in one direction, but sharp edges in another. The fololowing image contains motion blur:



Notice that the lower left and upper right edges of the circles are sharper than the upper left and lower right edges. That's because, in this image, the camera shake was on the diagonal. Camera shake can happen in any direction, but it's almost always in a single direction. And even if it isn't, there's always a pattern to the blur. The details in your images are uniformly blurred, which is not typical of camera shake.

In addition, while the blur around the blue and red text on the white background could be attributeable to either the lens' inherent softness or it's inherent chromatic aberration. the color halos in the white text on the gray background are characteristic of chromatic aberration.

 

[elty12345]

It is hand held at 1/125, best of 3. I don't think it is motion blur because the blurness is not directional.

 

[05_GD7]

1/125 at 250mm is pretty darn slow for handheld, especially for a sharpness test (using the 1/focal length rule of thumb as a baseline)

Suggest you use a tripod with a remote shutter release (or 10 sec timer) and get back to us.

 

[TCav]

1/125 at 250mm is pretty darn slow for handheld, especially for a
sharpness test (using the 1/focal length rule of thumb as a baseline)

Actually, that rule of thumb is for 35mm film and full frame dSLRs. For APS-C dSLRs, you should apply the "Crop Factor" of 1.5X to that. So at a focal length of 250mm, the shutter speed should actually be at least 1/375 second for handheld UNSTABILIZED shots.

But again, motion blur is mostly directional, and that's not the case here, so I don't think the slower shutter speed is a factor.

 

[Ed at Ridersite]

Focus on the center battery of an odd number lined up at a 45 degree angle to the camera. This will help identify all but the most minor BF/FF issues.

Minolta 50mm f1.7
A-100, f/1.7 @ 50 mm, 1/15, ISO 200



--
AEH
http://aehass.zenfolio.com/
Question: What do you do all week?
Answer: Mon to Fri. Nothing, Sat & Sun I rest!

 

[Crono_DL]

Just seems like a small bit of backfocus. As some others have noted, some of the text on the side of the bottle is sharper than the center. Either it's because the camera's focus spot covered a large area and chose to focus on the side, or the lens/camera has a small backfocus issue.

 

[TCav]

To check for Backfocus/Frontfocus problems, you can use the technique shown on http://www.focustestchart.com/ . It works as well or better than other methods, plus the test chart is all B&W, so it can also help you identify problems with chromatic aberration.

 

[WaltKnapp]

It is hand held at 1/125, best of 3. I don't think it is motion blur
because the blurness is not directional.

Not all motion blur is directional. There is multi directional motion blur, circular motion blur and so on.

Note also you are shooting a closeup with a lens who's optics are corrected for infinity shooting.

Walt

 

[TCav]

Not all motion blur is directional. There is multi directional
motion blur, circular motion blur and so on.

I'd be pleased if you could take the time to recreate some for us.

Thanks in advance.

 

[TCav]

Not all motion blur is directional. There is multi directional
motion blur, circular motion blur and so on.

Actually, no.

See http://digitalkamera.image-engineering.de/downloads/Golik_Boris_test_for_Image_Stabilizers.pdf

This study shows that tremors occur at a frequency of 8-12 Hz, and that the amplitudes of the pitch and yaw of the tremors coincided. In addition, any single tremor occuring at any shutter speed of less than 1/25 second would appear as a linear blur, or a smear of the image. That's not what we're seeing here.

Therefore, this cannot be motion blur.

 

[TCav]

In addition, any single tremor occuring at any shutter speed of less
than 1/25 second would appear as a linear blur, or a smear of the
image. That's not what we're seeing here.

That should read:

Therefore, any single tremor occuring at any shutter speed of less than 1/24 second, and possibly as long as 1/16 second, would appear as a linear blur, or a smear of the image. Therefore, multidirectional or circular blur due to camera shake could not occur in an image unless the shutter speed was significantly longer.

 

[WaltKnapp]

Therefore, this cannot be motion blur.

Oh I agree with this I agree with others that focus is off. I was just correcting the attitude that all motion blur is linear.

Walt

 

[TCav]

Oh I agree with this I agree with others that focus is off.

And so does the focus being off explain the color halos in the white text on the gray background?

These are characteristic of chromatic aberration, aren't they?

 

[elty12345]

I just use the focus test chart again, and it seems it is back focus by about 1cm on most test shot. Would this be a concern for this type of lens? (Outdoor vacation type)

Bought this as second hand so no return or anything.