Newbie Focus & Depth of Field Question

Lets say I have a row of 10 flowers in a garden and I want only the middle three to be in focus. How can I accomplish that? I've had some good luck figuring out aperture for blurring backgrounds and foregrounds but I haven't figured out how to keep the middle section of a shot in focus and everything else out of focus.

Set the smallest aperture you can, manually set the autofocus point so that the camera will focus on the center flower(s), and shoot. If you are limited to f/3 or 4, you might have to space the flowers a little farther apart to get the effect you want.
What lens are you using?

I have an S5 IS

Ah, it's not an SLR? I know nothing about the operation of P&S camera's. I suspect you can not do what you are trying with it though. Good luck!

c71clark wrote in post #4103711
Set the smallest aperture you can,

So that we don't all confuse each other with inconsistent use of terminology...

a 'small aperture', by convention, refers to the OPENING SIZE, not the numerical value of the f/number

So f/2 is a 'large aperture' but f/22 is not.

kev, search the web for a Depth of Field program, like f/Calc and others. It will help you to determine what f/stop is required in order to accomplish the goal you are asking about. The accomplishment of your stated goal is dependent upon
A) what aperture
B) what focal length of lens
C) what shooting distance
D) how far apart the nearest and farthest flowers are from each other which need to be in focus

I'm guessing you CAN accomplish what you'd like with your S5 since it has manual control. Set the aperture to the smallest f-number you can to give it the largest opening and, therefore, the shallowest depth of field. Play around with bumping up the ISO to say 400 since that should allow the lens to open up all the way. You want to hit the lowest f stop allowable by that lens.

Then compose your shot focusing on the middle flowers and shoot. The result will be the shallowest depth of field allowable by your camera. You can then use PP software of your choosing, like Picasa, to further blur out the remainder.

Alex

Let us assume that the center three flowers are 12" apart, and your distance from camera to the center one is 5'...

If 50mm lens on APS-C camera, at f/4 you can't get all three in focus...DOF = 4.8 - 5.2' !
If an 18mm lens, at f/4 you can get all three in focus...DOF = 3.9 - 7.0'

With the 50mm lens if you moved to 12' shooting distance you can get all three in focus...DOF = 11.0 - 13.2'

With a 50mm lens at 5' and f/11, you still cannot get all in focus...DOF = 4.5 - 5.6'

See how a DOF program comes in handy?...it proves that merely changing aperture is NOT going to necessarily have the desired effect!

Do the standards apply to lens' that cannot be removed? With a tiny sensor and much smaller lens-to-sensor distance, I would think the SLR method of calculating DOF would not apply.

The rules of DOF are universal...if they did not apply, you must be from a parallel dimension!

The parameters of DOF calculation are differerent for different sized formats (e.g. APS vs. 35mm vs. medium format). But the rule's equation is the same.

And, contrary to your question, lens-to-sensor is not the variable in DOF calculation, sensor-to-subject and FL and f/stop are the variables.


Unstated in most DOF calculations is the assumption that an 8x10 print at 'normal viewing distance' is inferred...but in truth, changing to a larger/smaller print size and changing the viewing distance to that print is important in actual DOF calculations for all situations that deviated from "8x10 print at 'normal viewing distance' "

Wilt wrote in post #4105685
The rules of DOF are universal...if they did not apply, you must be from a parallel dimension!

The parameters of DOF calculation are differerent for different sized formats (e.g. APS vs. 35mm vs. medium format). But the rule's equation is the same.

And, contrary to your question, lens-to-sensor is not the variable in DOF calculation, sensor-to-subject and FL and f/stop are the variables.

Unstated in most DOF calculations is the assumption that an 8x10 print at 'normal viewing distance' is inferred...but in truth, changing to a larger/smaller print size and changing the viewing distance to that print is important in actual DOF calculations for all situations that deviated from "8x10 print at 'normal viewing distance' "

OK so the reason the P&S have a larger DoF then 35ish mm is because of the size of their sensor not because of the distance of the sensor to the lens. Correct?

New Hobby wrote in post #4106052
OK so the reason the P&S have a larger DoF then 35ish mm is because of the size of their sensor not because of the distance of the sensor to the lens. Correct?

Correct! Size of sensor drives the FL of lens for a particular AOV, and together they drive the COC (by virtue of different magnification to achieve 8x10 final print) and the DOF

Here is a link to a DOF calculator.

The OP did not state that the flowers is going to lined up front to back or side to side.

With the G5 you're going to need to get as close as posible to the subject and set the lens to the widest focal length and largest aperature available to achieve desire blur, if the flowers are aligned front to back. The distance of the flower that you ant OOF must be far apart as well.

Thanks so much for the tips everyone! I guess I'll just have to go out and practice some of the suggestions you gave.