Moderators: richierich, ua900, PanAm_DC10, hOMSaR

 
ATAIndy
Topic Author
Posts: 653
Joined: Sat May 15, 2004 11:05 am

Lens Focus Question

Wed May 27, 2015 11:57 pm

I have a question regarding image focus that I've seen come up in my photos many times.

In the photo linked, you will notice that the "American" titles are pretty blurry yet the registration and tail look to be in focus. What is causing this change in focus across the length of the aircraft?

https://www.flickr.com/photos/ataindy/17554844984/

I've tried changing the aperture and shutter speed, but neither seem to make a difference. For more info, this particular photo was shot at f/8.0 at 1/640 and ISO 200.

Any info or advice is greatly appreciated. Thanks!
Boiler up!
 
mjgbtv
Posts: 1034
Joined: Mon Jan 28, 2008 2:18 am

RE: Lens Focus Question

Thu May 28, 2015 1:10 am

Some sort of distortion in the lens maybe? Everything on the left side of the image looks more blurry. It doesn't seem like you would have DOF issues with a side-on shot at f/8.0.
 
ATAIndy
Topic Author
Posts: 653
Joined: Sat May 15, 2004 11:05 am

RE: Lens Focus Question

Thu May 28, 2015 1:24 am

Quoting mjgbtv (Reply 1):
It doesn't seem like you would have DOF issues with a side-on shot at f/8.0.

I wouldn't think so either. I took several shots of the plane departing and had others where the entire aircraft is in focus, so I'm not sure its lens distortion.
Boiler up!
 
vikkyvik
Posts: 12573
Joined: Thu Jul 31, 2003 1:58 pm

RE: Lens Focus Question

Thu May 28, 2015 4:26 am

Is this cropped in at all, or is it the full crop?

Definitely looks like a lens issue. I've seen similar with my 70-200, though only sporadically (aka not enough for me to do something about it).

Is yours the 70-200 F4L?

Quoting ATAIndy (Thread starter):
For more info, this particular photo was shot at f/8.0 at 1/640 and ISO 200.

To be nitpicky, the EXIF shows ISO800, not 200. I thought it looked a bit noisy for 200.  
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
ATAIndy
Topic Author
Posts: 653
Joined: Sat May 15, 2004 11:05 am

RE: Lens Focus Question

Thu May 28, 2015 10:59 am

Quoting vikkyvik (Reply 3):
Is this cropped in at all, or is it the full crop?

Yes, it is cropped in slightly.

Quoting vikkyvik (Reply 3):
Definitely looks like a lens issue. I've seen similar with my 70-200, though only sporadically (aka not enough for me to do something about it).

Is yours the 70-200 F4L?

I'm using the Sigma f/2.8 70-200. Great lens that auto-focuses quickly, except for this issue.

Quoting vikkyvik (Reply 3):
To be nitpicky, the EXIF shows ISO800, not 200. I thought it looked a bit noisy for 200.

My mistake! Definitely not sunny enough for 200 that morning.
Boiler up!
 
dendrobatid
Posts: 1647
Joined: Sat Nov 06, 2004 3:40 pm

RE: Lens Focus Question

Thu May 28, 2015 12:37 pm

I would suggest uneven panning, even though you are at a reasonable shutter speed, the background is quite blurred as you would expect from a far lower shutter speed. This could explain why some images are ok, others not.
Panning takes practice and it is important to start with your hips parallel to the movement as any even slight inbalance can cause uneveness.

Mick Bajcar
 
User avatar
scbriml
Posts: 19029
Joined: Wed Jul 02, 2003 10:37 pm

RE: Lens Focus Question

Thu May 28, 2015 1:19 pm

Does this lens exhibit the same behaviour when shooting static planes at the same focal length? If not, then as Mick suggested, almost certainly down to panning technique.
Time flies like an arrow. Fruit flies like a banana!
There are 10 types of people in the World - those that understand binary and those that don't.
 
angad84
Posts: 2077
Joined: Mon Nov 05, 2012 3:04 pm

RE: Lens Focus Question

Thu May 28, 2015 3:09 pm

Quoting vikkyvik (Reply 3):
Definitely looks like a lens issue. I've seen similar with my 70-200, though only sporadically (aka not enough for me to do something about it).

This. I'm not sure it's down to the panning technique, as it looks like a softness/focus issue to one side of the frame, rather than blur.

I have experienced it with my 70-200 (F4L IS version) as well, but like Vik, only now and again, so not frequently enough to really be bothered.

Cheers
Angad
 
ATAIndy
Topic Author
Posts: 653
Joined: Sat May 15, 2004 11:05 am

RE: Lens Focus Question

Thu May 28, 2015 4:20 pm

Quoting scbriml (Reply 6):
Does this lens exhibit the same behaviour when shooting static planes at the same focal length? If not, then as Mick suggested, almost certainly down to panning technique.

No it doesn't, which suggests improper panning.

However... that usually results in soft/blurry areas that all streak in the motion I'm panning right? This just looks soft without motion blur. I may have to do some more concentrated research to root out the cause.

Thanks for the input everyone!
Boiler up!
 
vikkyvik
Posts: 12573
Joined: Thu Jul 31, 2003 1:58 pm

RE: Lens Focus Question

Thu May 28, 2015 6:24 pm

Quoting ATAIndy (Reply 8):
However... that usually results in soft/blurry areas that all streak in the motion I'm panning right? This just looks soft without motion blur.

That, and 1/640 is a pretty high shutter speed. You have to be doing something very wrong to get such a drastic difference from one side of the frame to the other.

Quoting angad84 (Reply 7):
I'm not sure it's down to the panning technique, as it looks like a softness/focus issue to one side of the frame, rather than blur.

Agreed.

Quoting ATAIndy (Reply 8):
No it doesn't, which suggests improper panning.

Not necessarily. It could be that the act of panning is causing lens elements to shift. Or something. That's just an untested hypothesis.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
angad84
Posts: 2077
Joined: Mon Nov 05, 2012 3:04 pm

RE: Lens Focus Question

Thu May 28, 2015 6:52 pm

Quoting vikkyvik (Reply 9):
Not necessarily. It could be that the act of panning is causing lens elements to shift. Or something. That's just an untested hypothesis.

Untested but likely - could be a stabilisation vs panning issue if it's an OS lens.

But if I recall correctly, your 70-200 is unstabilised, isn't it? Maybe it's just a combination of the focus motor, the focus element(s) and the motion of panning causing this issue.

Cheers
A
 
dendrobatid
Posts: 1647
Joined: Sat Nov 06, 2004 3:40 pm

RE: Lens Focus Question

Thu May 28, 2015 8:14 pm

I still suspect poor panning and it can be blur in more than one plane, up and down as well as side to side. However I think we also foget the camera as it is so easy to blame the lens. The position of the sensor is highly critical and if it is even very slightly out, a few microns, one side can be sharp, the other not - it could be slightly loose perhaps.

Some checks are needed with the camera on a tripod and a fixed object I think - try a newspaper fixed to a wall far enough away to fill the frame

Mick
 
vikkyvik
Posts: 12573
Joined: Thu Jul 31, 2003 1:58 pm

RE: Lens Focus Question

Thu May 28, 2015 9:55 pm

Quoting angad84 (Reply 10):
But if I recall correctly, your 70-200 is unstabilised, isn't it? Maybe it's just a combination of the focus motor, the focus element(s) and the motion of panning causing this issue.

Indeed, mine is unstabilized.

Quoting dendrobatid (Reply 11):
The position of the sensor is highly critical and if it is even very slightly out, a few microns, one side can be sharp, the other not - it could be slightly loose perhaps.

True, though I would think the lens could be calibrated to address this.
I'm watching Jeopardy. The category is worst Madonna songs. "This one from 1987 is terrible".
 
ATAIndy
Topic Author
Posts: 653
Joined: Sat May 15, 2004 11:05 am

RE: Lens Focus Question

Fri May 29, 2015 12:07 am

Quoting angad84 (Reply 10):
But if I recall correctly, your 70-200 is unstabilised, isn't it? Maybe it's just a combination of the focus motor, the focus element(s) and the motion of panning causing this issue.

Correct, it is unstabilized.

Quoting dendrobatid (Reply 11):
Some checks are needed with the camera on a tripod and a fixed object I think - try a newspaper fixed to a wall far enough away to fill the frame

I will have to try this, I guess there are many possibilities here. For reference, here is another shot at the 200mm focal length that looks just fine. https://www.flickr.com/photos/ataindy/16556053390

Again, I appreciate all the feedback, very helpful.
Boiler up!

Who is online

Users browsing this forum: qf789 and 10 guests

Popular Searches On Airliners.net

Top Photos of Last:   24 Hours  •  48 Hours  •  7 Days  •  30 Days  •  180 Days  •  365 Days  •  All Time

Military Aircraft Every type from fighters to helicopters from air forces around the globe

Classic Airliners Props and jets from the good old days

Flight Decks Views from inside the cockpit

Aircraft Cabins Passenger cabin shots showing seat arrangements as well as cargo aircraft interior

Cargo Aircraft Pictures of great freighter aircraft

Government Aircraft Aircraft flying government officials

Helicopters Our large helicopter section. Both military and civil versions

Blimps / Airships Everything from the Goodyear blimp to the Zeppelin

Night Photos Beautiful shots taken while the sun is below the horizon

Accidents Accident, incident and crash related photos

Air to Air Photos taken by airborne photographers of airborne aircraft

Special Paint Schemes Aircraft painted in beautiful and original liveries

Airport Overviews Airport overviews from the air or ground

Tails and Winglets Tail and Winglet closeups with beautiful airline logos