Focus - DPChallenge Forums

Pentax DA 18-55mm f/3.5-5.6 AF

05/03/2005 07:26:28 PM · #1

Is there some type of technique or formula to use when trying to get all subjects in focus and also achieve a blurred background?

For example, I shot a couple flowers the other day. One of the flowers was slightly closer to my camera than the other flower. I wanted a blurred background, so I needed a small aperture number (I shoot completely manual). So I couldn't just set the aperture to a large number, because I needed the blur. The result is that only one flower is in sharp focus.

How can I guarantee that I have a shot with both flowers in focus and the background blurred? Is it a matter of exposure bracketing, or the focus point, or both? If it is a matter of focus, where should the focus point be?

I never ran into this issue until that shot. Any ideas would be appreciated.

Message edited by author 2005-05-03 19:28:08.

faidoi

Pentax K10D

05/03/2005 07:34:55 PM · #2

That's the tough part about taking pictures of flowers.

05/03/2005 07:37:04 PM · #3

Originally posted by faidoi:

That's the tough part about taking pictures of flowers.

Well it wouldn't necessarily be flowers. In this case it was. But any photo with multiple subjects to keep in focus would tend to cause this problem.

Message edited by author 2005-05-03 19:37:24.

cpanaioti

Canon EF 70-300mm f/4.5-5.6 DO IS USM

05/03/2005 07:39:07 PM · #4

Distance from your subjects to the background could be an issue. If the background is too close then it's hard to get all of your subjects in focus while still rendering the background with enough blur.

Pentax DA 18-55mm f/3.5-5.6 AF

05/03/2005 07:40:04 PM · #5

You should have a preview button by the base of the lense and it allows you to preview your aperture and the resultant shot as the sensor will see it.

faidoi

Pentax K10D

05/03/2005 07:41:01 PM · #6

Originally posted by nfessel:

Originally posted by faidoi:
That's the tough part about taking pictures of flowers.

Well it wouldn't necessarily be flowers. In this case it was. But any photo with multiple subjects to keep in focus would tend to cause this problem.

I don't have manual focus on any of my cameras so I have to work on blurring in Photoshop.

It would be cool to see an example and the settings that you used for the shot. Don't forget to list the lens while you're at it. This way a better/more specific suggestion can be made.

faidoi

Pentax K10D

Pentax DA 18-55mm f/3.5-5.6 AF

05/03/2005 07:41:27 PM · #7

Originally posted by kawesttex:

You should have a preview button by the base of the lense and it allows you to preview your aperture and the resultant shot as the sensor will see it.

Depth of Field button?

05/03/2005 07:41:39 PM · #8

Originally posted by kawesttex:

You should have a preview button by the base of the lense and it allows you to preview your aperture and the resultant shot as the sensor will see it.

Yeah, sorry, I knew someone would say this. I forgot to mention, I do use the depth of field (aperture) preview, but it's not easy to tell at a glance. I am thinking that I may have to "focus bracket" the shots by using manual focus and changing the focusing for each exposure.

sabphoto

Samsung Galaxy S8/S8+

05/03/2005 07:41:53 PM · #9

check the threads for articles about Depth of Field (DOF) adjusting your f-stop will make your background in focus or not. Don't remember all the info about it but there is tons of info.

cpanaioti

Canon EF 70-300mm f/4.5-5.6 DO IS USM

05/03/2005 07:44:00 PM · #10

If you can control the distance between your subjects and the background then move them further away from it. This will give you more latitude with the depth of field.

05/03/2005 07:44:42 PM · #11

Yes, depth of field. Just to lazy to grab the book and had a brain freeze. :-)

05/03/2005 07:45:39 PM · #12

You haven't mentioned what lense you were using. Zoom?

05/03/2005 07:46:05 PM · #13

Originally posted by cpanaioti:

If you can control the distance between your subjects and the background then move them further away from it. This will give you more latitude with the depth of field.

That's a good point. Only problem there is in this instance, I would have had to rip the flowers out of the ground to distance them from the background. ;)

Message edited by author 2005-05-03 19:46:53.

05/03/2005 07:48:40 PM · #14

Originally posted by kawesttex:

You haven't mentioned what lense you were using. Zoom?

18-35mm kit lens for the eos 20d

05/03/2005 07:50:46 PM · #15

Originally posted by nfessel:

Originally posted by kawesttex:
You haven't mentioned what lense you were using. Zoom?

18-35mm kit lens for the eos 20d

Have you tried all (a few) different focal lengths?

05/03/2005 07:52:14 PM · #16

Originally posted by kawesttex:

Originally posted by nfessel:

Originally posted by kawesttex:
You haven't mentioned what lense you were using. Zoom?

18-35mm kit lens for the eos 20d

Have you tried all (a few) different focal lengths?

No I haven't tried that. It's actually an 18-55mm lens. That is also a good point though. Thanks. These suggestions will help me next time I run into this issue.

cpanaioti

Canon EF 70-300mm f/4.5-5.6 DO IS USM

05/03/2005 07:53:40 PM · #17

Originally posted by nfessel:

Originally posted by cpanaioti:
If you can control the distance between your subjects and the background then move them further away from it. This will give you more latitude with the depth of field.

That's a good point. Only problem there is in this instance, I would have had to rip the flowers out of the ground to distance them from the background. ;)

That's why I said 'if'. That means you need a longer zoom however this will play havoc on the DOF though may make the distance to the background a little less of an issue. ;o)

ganders

Tamron SP AF 28-75mm f/2.8 XR Di for Canon

05/03/2005 08:16:29 PM · #18

The 20D has the 'A-Dep' mode which (according to the manual) will select an aperture to get all the items you want within the focus field.

Can't say I've used it myself but the manual says it's there!

pitsaman

Canon EOS-30D

Canon EF 50mm f/1.8 II

05/03/2005 09:32:11 PM · #19

Lens distance to both flowers must be equal for same focus.

Blured background is good ,but sometimes background texture can add to the quality !

F 3.2

F 14

Message edited by author 2005-05-03 21:56:59.

kirbic

Canon EOS R5

Canon RF 24-70mm f/2.8 L IS

05/03/2005 09:38:10 PM · #20

Remember that for the same subject size in the frame (same subject magnification):
- Longer focal length = less DoF and greater subject distance
- Wider aperture = less DoF and closer subject distance
- Greater ratio of subject to background distance = more background blur
You can play with both focal length and aperture to get just the DoF you need.
Here is a cool little online DoF calculator that should help you to understand how changing some of these variables will change the DoF.