Help with aperture

lacied · 09-14-2010, 07:51 PM

Hello,
I am confused. I took the picture below at F/7.1 which I thought meant that the whole picture would be in focus. I can't even tell what IS in focus, but to me this looks more like a F/2.0 photo. I am new to this so excuse if my terminology is wrong or if I am totally backwards in my thinking, but I would really appreciate any help to clarify this for me. Thanks so much!
Taken with 18-55mm II kit lens at 47.5mm, ISO 400, f/7.1, 1/25 sec

Attached Images

KxBlaze · 09-14-2010, 08:14 PM

You focal length has to do with DOF too. The more you zoom in the less DOF you will have. Try taking that same pic but at 25mm or less and with 7.1 the entire pic should be in focus.

As for the pic not being in focus that is probably due to the 1/25 shutter speed. That is pretty slow and a little hard to hand hold.

So try the pic at 1/50 or faster and 20mm or less.

imtheguy · 09-14-2010, 08:42 PM

It also looks like you were very close which greatly impacts the DOF. If that shot was 24" away, the DOF for 50mm at f8 is only 4.7cm, less than 2 inches. If you have never done so, play with the online calculator linked below to get a feel for the relationships.

Depth of Field: Optical: Glossary: Learn: Digital Photography Review

lacied · 09-14-2010, 08:52 PM

Thanks so much for the information. Yes, I was very close to the subject but did not understand that it would make that much of a difference if the aperture was that high. I will check out that link also, thank you for that!

JeffJS · 09-14-2010, 10:22 PM

I was just going to say, I think you are too close to whatever you're taking a picture of. The closer you are, the more shallow your DOF, regardless of the lens itself. Here is a shot at f11 (with a macro lens).

The lens front is about 2 inches from the flowers.

Same lens and situation at f32

Same lens, f6.3

Peeper version

http://farm5.static.flickr.com/4108/4991801687_30a27a9f57_o.jpg

Completely different from your particular situation but I hope it demonstrates the point of Aperture vs Distance.

lacied · 09-15-2010, 08:29 AM

Thanks so much for the examples Jeff, beautiful photos! Seeing the different pictures with the info really helps!

Thanks again.

Marc Sabatella · 09-16-2010, 06:46 PM

f/7.1 is not particularly high. Closeup/macro photography is often done at f/16 or more.

09-14-2010, 07:51 PM	#1
lacied Inactive Account Join Date: Jan 2009 Location: Lafayette, LA Posts: 10	Help with aperture Hello, I am confused. I took the picture below at F/7.1 which I thought meant that the whole picture would be in focus. I can't even tell what IS in focus, but to me this looks more like a F/2.0 photo. I am new to this so excuse if my terminology is wrong or if I am totally backwards in my thinking, but I would really appreciate any help to clarify this for me. Thanks so much! Taken with 18-55mm II kit lens at 47.5mm, ISO 400, f/7.1, 1/25 sec Attached Images

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09-14-2010, 08:14 PM	#2
KxBlaze Veteran Member Join Date: Feb 2010 Location: California Photos: Gallery Posts: 1,602	You focal length has to do with DOF too. The more you zoom in the less DOF you will have. Try taking that same pic but at 25mm or less and with 7.1 the entire pic should be in focus. As for the pic not being in focus that is probably due to the 1/25 shutter speed. That is pretty slow and a little hard to hand hold. So try the pic at 1/50 or faster and 20mm or less.

09-14-2010, 08:42 PM	#3
imtheguy Site Supporter Join Date: Mar 2009 Location: Virginia Beach Photos: Gallery \| Albums Posts: 2,950	It also looks like you were very close which greatly impacts the DOF. If that shot was 24" away, the DOF for 50mm at f8 is only 4.7cm, less than 2 inches. If you have never done so, play with the online calculator linked below to get a feel for the relationships. Depth of Field: Optical: Glossary: Learn: Digital Photography Review

09-14-2010, 08:52 PM	#4
lacied Inactive Account Join Date: Jan 2009 Location: Lafayette, LA Posts: 10 Original Poster	Thanks so much for the information. Yes, I was very close to the subject but did not understand that it would make that much of a difference if the aperture was that high. I will check out that link also, thank you for that!

09-14-2010, 10:22 PM	#5
JeffJS Inactive Account Join Date: Aug 2008 Location: Michigan, USA Photos: Gallery \| Albums Posts: 7,484	I was just going to say, I think you are too close to whatever you're taking a picture of. The closer you are, the more shallow your DOF, regardless of the lens itself. Here is a shot at f11 (with a macro lens). The lens front is about 2 inches from the flowers. Same lens and situation at f32 Same lens, f6.3 Peeper version http://farm5.static.flickr.com/4108/4991801687_30a27a9f57_o.jpg Completely different from your particular situation but I hope it demonstrates the point of Aperture vs Distance.

09-15-2010, 08:29 AM	#6
lacied Inactive Account Join Date: Jan 2009 Location: Lafayette, LA Posts: 10 Original Poster	Thanks so much for the examples Jeff, beautiful photos! Seeing the different pictures with the info really helps! Thanks again.

09-16-2010, 06:46 PM	#7
Marc Sabatella Veteran Member Join Date: Sep 2006 Location: Denver, CO Photos: Gallery Posts: 10,685	f/7.1 is not particularly high. Closeup/macro photography is often done at f/16 or more.