Playing with DOF

[ricohcam01]

Hey guys I am trying to figure out why in this image the thumb is out of focus. Can anyone tell me? The focus point was on the top of the middle finger?

[dwterry]

Three important questions: 1) Focal length, 2) Aperture, and 3) Distance to subject

From your post, let's guess that you are using the 50mm 1.8 lens, that you've opened it up all the way to 1.8, and that your distance to subject is 3 feet. If all three of those items are true, then your "Depth of Field" is a mere 0.84 inches. If the hand is closer than 3 feet, then it's even LESS than that. The closer the subject, the shallower the depth of field.

Here is an online Depth of Field Calculator (http://www.dofmaster.com/dofjs.html) for you to play with.

[PEACHMAN]

Hey Mr DWTERRY...the page to the calculator comes up missing on my screen....But I'd love to see it...Thats a pretty close DOF calculation you can do .84" ? man that's a lot tighter than I would have imagined...I need a calculator !

[Andy_T]

Peachman ... works on my PC.


Terry explained it marvellously...
Most likely the DOF was too shallow to get the hand in focus.

When you're very close, the DOF is very short ... as you'll realize when entering the values in the calculator.

Best regards,
Andy

[Curtis N]

I need a calculator !Try this one (http://boonecounty.info/photocalc.htm).

[PEACHMAN]

Hey Mr DWTERRY...the page to the calculator comes up missing on my screen....But I'd love to see it...Thats a pretty close DOF calculation you can do .84" ? man that's a lot tighter than I would have imagined...I need a calculator !

Hey Mr DWTERRY...I can get that page w/ the calculator now ...must have been my server....wow...that's the easiest one I've seen...any idea if this is available to go on a palm pilot or some other portable calculation that is smaller than a laptop ??

[dwterry]

any idea if this is available to go on a palm pilot or some other portable calculation that is smaller than a laptop ??

The top left portion of that page has a link to a Palm version of the calculator. Here's the link (http://www.dofmaster.com/custom3.html).

I personally use a different one on my Dell Axim (Windows CE), but I can't remember where I got it from. I carry it with me everywhere. It helps when I'm doing a group shot to make sure that I have enough DOF to get the entire group.

[PEACHMAN]

The top left portion of that page has a link to a Palm version of the calculator. Here's the link (http://www.dofmaster.com/custom3.html).

I personally use a different one on my Dell Axim (Windows CE), but I can't remember where I got it from. I carry it with me everywhere. It helps when I'm doing a group shot to make sure that I have enough DOF to get the entire group.

Wow, thanks !!:D :D Better day than I expected !!