Question about image quality

[sraulers]

I took the photo below from my truck window while driving through the Fort Worth Nature Center. When I got home and downloaded it I was disappointed to see that I didn't get the focus right on the deer. My bigger concern though is the "texture" in the background... the blurred background almost appears to have a corduroy texture to it. I'm not sure if this is a problem with the lens or if it was a combination of lighting/focus/movement/nut behind the wheel/etc.



I was using my Tamron 70-300mm lens at 300mm. Light was fading (about 5:00PM) and I had the hood on the lens. I was using Auto Exposure so the settings were 1/320s @ f5.6 (ISO 800).

I've never seen this effect on previous shots with this lens. I'm going back out today to shoot some more with it and maybe it'll prove to be nothing. Just curious if any of you have seen the textured effect before and if so, what it's caused by...

Thanks,

Steve R.

[engstrom]

Steve, that's quite an interesting effect. I don't think I've seen that before. Was the window rolled down when you took that shot?

[PictureCow]

It looks to me like a Circle of Confusion issue...

Here's a pretty decent link that explains what CoC are and how they happen... I believe your lens and camera are fine.

http://www.northnet.org/jimbullard/CoC.htm

Hope this helps! :)

[sraulers]

Thanks for your replies...

John: Yes, the window was open, though I have to admit it occurred to me also. I took a couple of shots of the neighbor's dog on my return from the Nature Center. This one has the same effect with the dog standing in the open and no sunlight filtering through trees:



Color me still confused...

PictureCow: Thanks for the link... I'll have to study up on CoC. Unfortunately I didn't get a chance to shoot any photos today using that lens. I'll have to give it a shot tomorrow.

Thanks again for taking time to reply... much appreciated!

- Steve R.

[Roy]

I've never seen that effect but I'd like to know what's causing it as well. Is the problem just when using the Tamron lens? Hope you get it figured out and keep us updated.

If it's not some freek thing causing that effect, I'd be on the phone with Tamron first thing Monday morning.

[Norm]

What iso was dog shot?

Were you using a filter on either shot?

Have you tried another lens and a lower iso?

Doesn't look good.

[sraulers]

Norm: The dog was shot at ISO 640... another Auto Exposure shot. The shutter speed was 1/500s and the aperture was f5.6. No flash; AntiShake was on. He was also shot at 300mm.

Roy: As far as I know it's just the Tamron, but I'm planning to do some testing tomorrow to see for sure. I'll report back then...

Here's a shot of the family cat, taken after the Nature Center and just before the dog. Settings were 1/200s @ f5.6, ISO 800. Same effect...



Oh, well! Guess I'll sleep on it tonight and check it out tomorrow...

Thanks guys!

- Steve R.

[Norm]

From these small pics, it doesn't seem that the focus is very sharp either.

[engstrom]

Steve, please let us know the results of tests with other lenses. Now you have my curiosity up!

[DEMDeepEllumMusic]

Curious, was the car running at the time that you were shooting through the window? Could be caused by very small vibrations of the car running.
Put the lens on a tripod outside, get the cat to co-operate or go grab a garden gnome or the spouse and try a shot similar to that of the cat and see if the same problem occurs.

[srwatters]

It appears to me to be the effect known as banding. Certain pattern and electronics combinations can cause the software in the camera to produce this anomaly.

Earlier in this thread the concept of CoC or circle of confusion was brought up. While a very technical concept, the web page referenced does NOT do a very good job of describing what it means for the photographer. First it is not a bad thing or an effect that happens to some images. All images are dependent on the CoC that is created by the lens/aperture/focal distance/media that are used. I don't have a great place to point you to, but maybe John Engstrom can help John?

[engstrom]

This is a website that talks abou aperture, focal plane, CoC and how they affect the depth of field in the picture:
http://dspace.dial.pipex.com/town/pi.../DOF%20how.htm

Unfortunately I haven't found a website that goes into all the technical details of focal length, aperture, distance to subject, sensor size, ISO and how all those things affect the CoC (and thus DOF) and exposure but I do know of a plan by a talented photographer to put together a series of essays covering those topics.

[PictureCow]

I still vote for CoC! Have your tried shooting other focal lengths and apatures yet? Curious minds want to know!

[Redmouse]

The pattern seems consistent. Kinda like the motion blur that I typically get shooting at at slow speeds. The Minolta 5D looks like it has an anti-shake built in. It looks like you are shooting at speeds fast enough that you dont need it. Have you tried to disable it when you're shooting?

[krodgers]

i would take the same lens out and try varying all the setting (iso, fstop, shutterspeed, AS) might even do your test on a constant back ground such as a sheet and if it does same on all take the lens back and get another, or even if it does it just on one particular setup still take it back.