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Focus issues - what am I doing wrong???

maiast
Apprentice

Hello to this wise group! I am serious photo hobbyist and have a solid understanding of how aperture, shutter speed, one shot vs. al servo focusing, focusing points and all those key elements work together, but I still keep messing up with my focus! I primarily use a 5D Mark III and Tamron SP AF 28-75mm f/2.8, no flash (working on that!). I think sometimes when using one-shot I don't grab my subject's eyes with my center focus point, so I'm working on that. But when zoomed out to 70mm, at least 15 feet away, shouldn't my depth of field be enough that even if I am focused on my subject's chest, I would still have a crisp face with f4? What about f5.6? Most of you portrait photographers seem to be able to get both nose and eyes in focus with an 2.8 100mm or greater, even standing close enough to just capture head and shoulders! I even see wedding pictures shot at 1.4 or 2.8 and both bride and groom seem to be crisp. I do a lot of low-light work (like the dance team in the school gym) so I need to figure out how to use my wider apertures more successfully. 

 

I'm hoping that you would look at these three un-retouched shots and help me understand. Pic of favor bags shot at 75mm ISO 400 1/250 f4. I'm surprised that I don't have enough depth of field for both the center bags to have crisp lettering. It's clearly focused on the bag that's right of center, and the bag that's left of center is blurry although it's only maybe an inch closer to lens. Prom one was an experiment with ISO 1250 1/400 f8 and to my eye, while my daughter's flowers pop (I must have focused there) their faces are relatively soft - at f8!! I would chalk it up to noise from the high ISO except that to me her flowers do look really sharp. Last one 75mm ISO 2000 f5 1/320 - I don't get this one at all! Maybe sharp on a patch of my daughter's hair on the left, maybe the shoe at the bottom, but nowhere else. I've been using silly high ISOs out of fear that I was losing sharpness to slow shutter speeds.

 

HELP! What am I overlooking? Or is it just time to upgrade my lens? So grateful for your insights.

 

Maia

https://www.dropbox.com/s/c8an3fjkqodubv5/1Y9A2075%20%281%29.jpg?dl=0

 

7 REPLIES 7

cicopo
Elite

This may help decide if it's a DOF problem or a lens issue.

 

http://www.dofmaster.com/dofjs.html

"A skill is developed through constant practice with a passion to improve, not bought."

Thank you so much for your reply! I have been referring to that quite a bit and it leads me to believe it's my lens, but I thought that perhaps I wasn't being accurate in my guesstimates of how far I was from my subject, or how many inches there are on the plane between someone's chest and eyes. It also seems like I don't have the problem as much in brighter light and lower ISOs. I may try renting a better lens to see if I have the same problem. I appreciate the suggestion! 


@maiast wrote:

Thank you so much for your reply! I have been referring to that quite a bit and it leads me to believe it's my lens, but I thought that perhaps I wasn't being accurate in my guesstimates of how far I was from my subject, or how many inches there are on the plane between someone's chest and eyes. It also seems like I don't have the problem as much in brighter light and lower ISOs. I may try renting a better lens to see if I have the same problem. I appreciate the suggestion! 


Have you checked your autofocus microadjustment? If it's off, it could make your DOF seem shallower than it actually is. The 5D3 lets you set AFMA at both ends of the zoom range, providing greater accuracy than most older cameras allow.

Bob
Philadelphia, Pennsylvania USA

Thank you - I have not yet checked that so I'll look into it!


@cicopo wrote:

This may help decide if it's a DOF problem or a lens issue.

 

http://www.dofmaster.com/dofjs.html


I have found that to be a surprisingly useful site.  I prefer the tabular format, over the form that you posted.

 

http://www.dofmaster.com/doftable.html

 

Using my old tape measure from my track and field officiating days, I can get some pretty accurate measurements.

--------------------------------------------------------
"The right mouse button is your friend."

One of these days I'll modernize but I still use a cell phone that isn't much more than a phone & regular computers / laptops so no looking on a tablet I don't yet own. I did get my wife a tablet for Christmas primarily so she can show off the photos of the grandkids. It's basic & uses the internet via my router but not via call towers.

"A skill is developed through constant practice with a passion to improve, not bought."


@cicopo wrote:

One of these days I'll modernize but I still use a cell phone that isn't much more than a phone & regular computers / laptops so no looking on a tablet I don't yet own. I did get my wife a tablet for Christmas primarily so she can show off the photos of the grandkids. It's basic & uses the internet via my router but not via call towers.


We're in the same boat, you and I.  Just last year, my son cheered when I finally had to retire my cell phone, which had a "green screen", in favor a smart phone with a hi-res color display.  I only use it as an emergency car phone, just like the old one.

 

I, too, recently bought a 2-in-1 tablet that ran Windows 8, which I later upgraded to Windows 10.  It fits in my camera bag much better than my laptop.  I think the last time I turned it on was last fall.  The display is too small for aging eyes, and my bologna fingers don't do the gesture dances very well.  Gimme a mouse, a keyboard, and a monitor, man!

--------------------------------------------------------
"The right mouse button is your friend."
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