Nov 24, 2014, 06:58
Hi Ed,
must mention forward or back focus is not a Sigma thing - I had/have Sigma lenses which are superb. The more you push the equipment the more likely manufacturing and design tolerances could be exposed. Also, the fact that Canon and Nikon both include micro focus adjustment on their more advance cameras confirm to me that it is not a 'Fit for Purpose' issue.
Speaking entirely for myself, when i had the 650D I tended to use Program mode, all focusing points, and auto ISO, which worked well most of the time and the computer did most of the work to prevent glaring mistakes on focus and exposure.
As I became more knowledgeable/picky/competent/pedantic (select your own preference) I wanted to do more myself so now tend to use Aperture or Time, single focus point, and either auto or manual ISO as I think best.
Returning to focusing issues, as an example: a 400mm lens at f5.6 (common max aperture of zoom lens), focused at 5m has a depth of field of just 4cms. [see http://www.silverlight.co.uk/resources/dof_calc.html]
It is universally advised by experts (not amateurs like me) that the eyes must be sharp. At that range on a large animal that is less than the difference between the eyes and the nose tip. a 3cm focusing error - human or camera just misses.
Here are 2 of my favourites which I think show what I mean:
full image
7D, Sigma 120-400 at 160mm 1/500 f4 ISO 1000, in shade, single focus point on the eye, hand held, range about 4m so DoF about +/- 6". Note on the 100% crop the eye is sharp as is the ear and whiskers, but see how the back ear is out of focus. Wouldn't look the same if back ear not eye was in focus
Also full image
7D, Sigma 120-400 at 350mm about 10m I recall, 1/500, f8, ISO 3200 hand held, nearly dusk. On the 100% crop the eye is sharp but there is load of noise - not apparent on a 7x5 print but certainly shows up on an A3+
So we pay our money and take our choice I guess, but returning to John's original question and having looked at his flicker pages, there is some pretty impressive stuff there. I particularly liked many of the birds in flight (which I find difficult) and close ups - which just goes to show that expensive kit isn't everything - an eye for a picture, good technique, subject knowledge, patience have a little bit to play also
must mention forward or back focus is not a Sigma thing - I had/have Sigma lenses which are superb. The more you push the equipment the more likely manufacturing and design tolerances could be exposed. Also, the fact that Canon and Nikon both include micro focus adjustment on their more advance cameras confirm to me that it is not a 'Fit for Purpose' issue.
Speaking entirely for myself, when i had the 650D I tended to use Program mode, all focusing points, and auto ISO, which worked well most of the time and the computer did most of the work to prevent glaring mistakes on focus and exposure.
As I became more knowledgeable/picky/competent/pedantic (select your own preference) I wanted to do more myself so now tend to use Aperture or Time, single focus point, and either auto or manual ISO as I think best.
Returning to focusing issues, as an example: a 400mm lens at f5.6 (common max aperture of zoom lens), focused at 5m has a depth of field of just 4cms. [see http://www.silverlight.co.uk/resources/dof_calc.html]
It is universally advised by experts (not amateurs like me) that the eyes must be sharp. At that range on a large animal that is less than the difference between the eyes and the nose tip. a 3cm focusing error - human or camera just misses.
Here are 2 of my favourites which I think show what I mean:
full image
7D, Sigma 120-400 at 160mm 1/500 f4 ISO 1000, in shade, single focus point on the eye, hand held, range about 4m so DoF about +/- 6". Note on the 100% crop the eye is sharp as is the ear and whiskers, but see how the back ear is out of focus. Wouldn't look the same if back ear not eye was in focus
Also full image
7D, Sigma 120-400 at 350mm about 10m I recall, 1/500, f8, ISO 3200 hand held, nearly dusk. On the 100% crop the eye is sharp but there is load of noise - not apparent on a 7x5 print but certainly shows up on an A3+
So we pay our money and take our choice I guess, but returning to John's original question and having looked at his flicker pages, there is some pretty impressive stuff there. I particularly liked many of the birds in flight (which I find difficult) and close ups - which just goes to show that expensive kit isn't everything - an eye for a picture, good technique, subject knowledge, patience have a little bit to play also