Do You Really Need Fast Glass

[RAZKY]

One of those photo words I have no idea what it means. What's a bokeh? Nice photo BTW!

Bokeh - Wikipedia

en.wikipedia.org

 

[Don Fischer]

Bokeh - Wikipedia

en.wikipedia.org

Thank you!

 

[greybeard]

One of those photo words I have no idea what it means. What's a bokeh? Nice photo BTW!

Bokeh is blurry background. Faster glass has a shallower Depth of Focus when you shoot at wider f/stops like f/1.8. so it is easier to blur the background.

 

[RAZKY]

It's that time of the year again when I re-evaluate my equipment and succumb to gas pains. I've been drooling over this one since release, Pentax HD PENTAX-D FA* 85mm f/1.4 ED SDM AW Lens but do I "really" need it???? I already have a pretty full stable at my disposal, some of which encompass the 85mm focal range and of late I'm beginning to even question the need for the fast glass I already have.

Most of my photography uses supplemental light and the high ISO capability of my cameras makes it hard to justify the large cash outlay. Rarely do I shoot wide open, especially on portrait work as I'm not a fan of only partially having the face in focus, Bokeh/OOF blur aren't necessarily an issue if you adjust your distances to achieve the DOF, and raising the ISO eliminates low light problems. Then you get into into the weight factor, like most fast glass this thing weighs in just under 3 lbs, add another 2+ lbs for the body, that's a lot. By comparison the 70-200 f2.8 is just under 4lbs, and from experience I find myself not using it as much, because the the weight is a PITA.

So how many others are questioning the benefits?

Bokeh is blurry background.

With such misinformation as this, little wonder many folks are confused as to what bokeh is! (Please see the Wikipedia article posted above.)

 

[smoke665]

Faster glass has a shallower Depth of Focus when you shoot at wider f/stops like f/1.8.

Shooting at wider apertures decreases the DOF on any lens, not just those that have a wider aperture, and you left out distance to subject as the other determining factor of DOF. If my math is right a 50mm lens focused on an object at 48" at f/1.4 has a DOF of just under 1 1/4". The same lens at f/5.6 focused on an object at 24" has the same DOF. The only difference between the shots is the FOV (Field of view).

Worth noting in addition to Razky's link, Bokeh is the aesthetic quality of all OOF which could be both foreground and background.