lenses and focus adjustment

everydaylife · 09-03-2014, 06:35 PM

I was reading about the FA*85 f1.4 at this site Stan's Pentax Photography and there is the opinion that the this particular lens was designed so that when the lens is focused the subject is at the back edge of the zone of focus so that the DOF extends to well in front of the subject focused on thus making background as blurred as possible.

With cameras now having in body focus adjustment is incorporating this design in a lens redundant. Does this mean that individuals could using in body AF adjustment adjust there lenses to have this effect. I would think that setting a lens up to slightly front focus would have the same effect. Am I correct?

fgaudet · 09-03-2014, 07:59 PM

Originally posted by everydaylife

this particular lens was designed so that when the lens is focused the subject is at the back edge of the zone

Well, wait... what?

Originally posted by everydaylife

I would think that setting a lens up to slightly front focus would have the same effect. Am I correct?

If you set your lens to front focus, well, your subject won't be in focus... I doubt that a few microns adjustment will have any effect on perceived blur... But it will have an effect on subject sharpness...

Use your feet and move a bit closer to your subject or get your subject to distance itself (if possible) from the background... It's a much better and simpler way of increasing the blur...

SpecialK · 09-03-2014, 09:38 PM

Originally posted by everydaylife

I was reading about the FA*85 f1.4 at this site Stan's Pentax Photography and there is the opinion that the this particular lens was designed...

"In close to mid distance shooting, the 85 f1.8 puts the subject in focus more towards the middle of depth of field than the f1.4 version, which appears to somehow put it more towards the back edge."

The guy (in 1999) did not say he thought it was designed that way, but that the lens did something particular. Hopefully he has A) come to his senses, B) gotten his lens fixed, or C) gotten a body with AF calibration in the last 15 years. If you manually focus (don't all portrait artists do that with a thin DOF, anyway) how is the lens going to change the focus point on you?

09-03-2014, 06:35 PM	#1
everydaylife Senior Member Join Date: Sep 2011 Photos: Gallery \| Albums Posts: 268	lenses and focus adjustment I was reading about the FA*85 f1.4 at this site Stan's Pentax Photography and there is the opinion that the this particular lens was designed so that when the lens is focused the subject is at the back edge of the zone of focus so that the DOF extends to well in front of the subject focused on thus making background as blurred as possible. With cameras now having in body focus adjustment is incorporating this design in a lens redundant. Does this mean that individuals could using in body AF adjustment adjust there lenses to have this effect. I would think that setting a lens up to slightly front focus would have the same effect. Am I correct?

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09-03-2014, 07:59 PM	#2
fgaudet Veteran Member Join Date: Oct 2013 Location: Ontario Posts: 726	Originally posted by everydaylife this particular lens was designed so that when the lens is focused the subject is at the back edge of the zone Well, wait... what? Originally posted by everydaylife I would think that setting a lens up to slightly front focus would have the same effect. Am I correct? If you set your lens to front focus, well, your subject won't be in focus... I doubt that a few microns adjustment will have any effect on perceived blur... But it will have an effect on subject sharpness... Use your feet and move a bit closer to your subject or get your subject to distance itself (if possible) from the background... It's a much better and simpler way of increasing the blur...

09-03-2014, 09:38 PM	#3
SpecialK Pentaxian Join Date: Dec 2006 Location: So California Photos: Gallery Posts: 16,480	Originally posted by everydaylife I was reading about the FA*85 f1.4 at this site Stan's Pentax Photography and there is the opinion that the this particular lens was designed... "In close to mid distance shooting, the 85 f1.8 puts the subject in focus more towards the middle of depth of field than the f1.4 version, which appears to somehow put it more towards the back edge." The guy (in 1999) did not say he thought it was designed that way, but that the lens did something particular. Hopefully he has A) come to his senses, B) gotten his lens fixed, or C) gotten a body with AF calibration in the last 15 years. If you manually focus (don't all portrait artists do that with a thin DOF, anyway) how is the lens going to change the focus point on you?