Canon EF 85mm f/1.8 USM

[futureal33]

Originally Posted by gonzogolf

Its not the lenses that are at fault here. Its technique. With that composition your focus point may be larger than the thing you are trying to focus on.

Id agree with you that the technique could potentially cause back focus (ie, focus point at that FL is around the size of her entire head, so it could lock onto something contrasty behind her head) but what I am getting is front focus (consistently at this focal length, but NOT at closer focal length - which doesn't make sense)

[gonzogolf]

Originally Posted by futureal33

Id agree with you that the technique could potentially cause back focus (ie, focus point at that FL is around the size of her entire head, so it could lock onto something contrasty behind her head) but what I am getting is front focus (consistently at this focal length, but NOT at closer focal length - which doesn't make sense)

Yes, it does. At closer focal lengths the things you are focusing on are more magnified. Hence you more accurately focus on them as your likelihood of getting your focus point on the thing you want.

[futureal33]

What technique would you use to do a full length portrait at f1.4 (or similar), where you want the eyes sharp? Perhaps I am doing something wrong, as it has happened with two lenses - so the common theme is me, not the lens! Would appreciate any tips/suggestions

Thanks

[gonzogolf]

Originally Posted by futureal33

What technique would you use to do a full length portrait at f1.4 (or similar), where you want the eyes sharp? Perhaps I am doing something wrong, as it has happened with two lenses - so the common theme is me, not the lens! Would appreciate any tips/suggestions

Thanks

Are you focus recomposing?

[futureal33]

Originally Posted by gonzogolf

Are you focus recomposing?

No, not unless I absolutely cannot help it. I use a 5DmkIII and find that in portrait orientation, the highest row of focus points are right on the subjects eye when doing a full length body portrait - worst case scenario is focus with top row of points, then recompose a few mm. I rarely use the middle focus point and then recompose that much.

[gonzogolf]

Originally Posted by futureal33

No, not unless I absolutely cannot help it. I use a 5DmkIII and find that in portrait orientation, the highest row of focus points are right on the subjects eye when doing a full length body portrait - worst case scenario is focus with top row of points, then recompose a few mm. I rarely use the middle focus point and then recompose that much.

Next time you are out, try focusing on something that will serve as substitute for the eye. At full body crop size the eye is much smaller than the focus point (the point is larger than the red square in some cases) which means you might be focusing on the nose or forehead instead of the eye. At 1.8 you have precious little margin for error. Maybe move down a bit and hit the cheek, sometimes the neck will be on the same plane as the eye depending on the pose.

[vinmunoz]

^^^good tip. thanks...

[futureal33]

Thats a great tip - thank you.
Must admit, at full length body portrait crop, the DOF at 1.8 should be sufficient to get a sharp whole head in I would have thought - need to check DOFmaster to confirm

[gonzogolf]

Originally Posted by futureal33

Thats a great tip - thank you.
Must admit, at full length body portrait crop, the DOF at 1.8 should be sufficient to get a sharp whole head in I would have thought - need to check DOFmaster to confirm

DOfmaster will give you the range of acceptable sharpness, but if you are looking for tack sharp eyes you still have to nail the focus. Have you micro adjusted the lens in question?

[futureal33]

Originally Posted by gonzogolf

DOfmaster will give you the range of acceptable sharpness, but if you are looking for tack sharp eyes you still have to nail the focus. Have you micro adjusted the lens in question?

There lies the issue... at close range focus is fine - it needs no micro adjust... however at longer range I am experiencing problems.

[BB Snapshots]

Lou by Brian.Buckler, on Flickr


183/366 - Golden (Week 26 - Weigh-in) - Halfway Point! by Brian.Buckler, on Flickr

[AnnieMacD]

3-shot pano.


The Cloud by AnnieMacD, on Flickr

[ericm678]

Loving this lens!

[rpolitsr]

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Canon EF 85mm f/1.8 USM (II)
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