Why isn't this sharp?

[A/Ox4]

Can anyone help me understand why this photo is not sharper? This is a problem I have, where my photos do not come out as sharp as I think they should.

I'm looking specifically at the "paramedic" patch on the shoulder.

Shot on a D750, Tamron 70-200

1/500th, f/8, ISO 100, 185mm

untitled-1117.jpg

 

[Derrel]

Kind of difficult to tell actually, but the upper left corner, and the EMS guy in the vest look blurred, while the BP cuff and the fellow on the right look adequately sharp. Perhaps it is just that the EMS fellow and the firefighter behind him are simply not within the DOF band? The lens compression makes the EMS guy and the patient appear close to one another in terms of distance, but the long focal length is compressing the scene, and it's clear that the EMS guy in the vest is the closest subject. FOCUS appears to be on the blood pressure cuff, and that looks sharp, while the EMS guy's right arm is clearly out of focus.

Also--this is a significantly down-sized image; I think the down-rezzing and the sharpening applied might not be quite optimal for this image.

There are other possibilities besides a shallow DOF band: decentered lens element, or perhaps a problem with VC being enabled at that fast a shutter speed, or perhaps even a lens mount alignment issue. Let's hope this is just a DOF issue!

Having VR or IS or VC engaged at speeds in the 1/500 and faster range CAN cause softening issues! I know this from very regrettable personal experiences from the early 2000's era.

 

[ronlane]

What Derrel said. It appears to me that the BP cuff was where you focused and that the compression has something to do with the DOF and blurring.

 

[A/Ox4]

I'll open my DOF calculator and see how big my DOF should be. I didn't thing about VC being on, I suppose I could try turning that off. Honestly, lense mount/element issues could be very real. Most of what I do is fireground photography and my equipment gets beat up. They are insured however.

Also, the link in my original post is to flicker where a full size file may be viewed.

Edit: according to a DOF calculator, my DOF may have only been about 6 inches.

 

[astroNikon]

as above

The EMS's guy arm hair is blurred in comparison the the Fireman arm/pressure cuff

What focusing mode were you in ?
do you know your exact focus spot ?

 

[A/Ox4]

as above

The EMS's guy arm hair is blurred in comparison the the Fireman arm/pressure cuff

What focusing mode were you in ?
do you know your exact focus spot ?

Single point spot focus. I don't, but isn't that embedded in the meta data?

 

[wfooshee]

As stated, and as you calculated, that's simply very shallow depth of field. The cuff, the guy on the right's hair, and his shirt are all quite sharp, but his far arm is showing out-of-focus. The other two guys are in front of and behind the depth-of-field region. I don't see this as a lens problem at all. EXIF says Approximate focus distance 5.96. Is that meters, I guess? So less than 20 feet, zoomed almost all the way out, giving you almost the shallowest depth of field you can get, long lens up close.

 

[A/Ox4]

I think I simply overestimated my DOF. I will have to try f11, maybe f16?

 

[weepete]

Yeah, a DoF issue I think. Possibly a little back focusing too, at f8 I'd have expected that to be sharp as well at 185mm. Like was said it's difficult to tell at that resolution.

 

[wfooshee]

Load up the calculator again, see what it says?

 

[A/Ox4]

Yeah, a DoF issue I think. Possibly a little back focusing too, at f8 I'd have expected that to be sharp as well at 185mm. Like was said it's difficult to tell at that resolution.

You can check the high resolution on Flickr, I've provided a link.

Also, my lense is going for repair. its been dropped many a time simply due to the environment I often shoot in.

 

[weepete]

Thanks mate, I missed that first time. The cuff loks pin sharp, the face of the paramedic and his collar looks ok to me just when it goes to the high vis it starts looking a bit oof. Given the distance and bearing in mind that straight on shots look shorter anyway I'd guess that your dof was around 5ft (+ or - one). I'd try f11 first but f16 looks like the one for these shots as you say.