How do I?

[poppy]

I can't figure out where exactly to put this questions. I'm sorry if it is in the wrong place. I am trying to take a photo with the background and foreground blurred, but the subject in focus. How do I do that? Part of the assignment for this online photography class is I have to take it all in manual. I kind of feel like I am cheating, but I am so stumped. HELP!!!!

[klam]

The way I would do it is to open up my aperature all the way so I would get a shallow depth of field. Then adjust my shutter speed to get the correct exposure

[kencaleno]

If you don't have a Fast (F1.4;1.8;2.8) lens,then in photoshop:

Faux F1.8 D.O.F.

1. Ctrl+J ; Add a layer mask-Using Pen tool, draw a path around subject, Edit> fill Black 100%
2. Selection> save selection, save to new channel
3. Select gradient tool, black to white, linear
4. From the area you want in focus, draw a line vertically downwards (1/3 in front;
5. Using gradient tool again, layer mode Screen, drawing a line upwards 2/3ds behind)
6. Channels-click on saved mask Ctrl+ click-select gradient mask, mask only
7. Set background color to black. Ctrl+ backspace
8. Click on original duplicated layer with its mask-name it “Gaussian Blur”
9. Now select image-not mask.-Lock Transparency. click little chequerboard, at top of layer palette
10. Filter> Blur> Gaussian blur 40-50 pixels
11. Repeat step 8,but name layer “Lens Blur”-Filter> blur> lens blur, and in the dialogue box:
12. “faster”, depth map source “layer mask” Blur focal distance-adjust to suit
13. Set iris shape to number of diaphragm blades of your lens. Radius 100%
14. Don’t play with “blade curvature or rotation” Brightness 2;Threshold 180
15. Click Ok-Flatten and save

[Samanax]

Originally Posted by poppy

I can't figure out where exactly to put this questions. I'm sorry if it is in the wrong place. I am trying to take a photo with the background and foreground blurred, but the subject in focus. How do I do that? Part of the assignment for this online photography class is I have to take it all in manual. I kind of feel like I am cheating, but I am so stumped. HELP!!!!

Which lens do you have for that XSi? Need to know the exact model with f/stop info.

What you want to do is set your aperture to the biggest opening it's got (small f/stop number), set the ISO to 100 if shooting in bright light or ISO 200 if shooting in good light (not bright sunlight) and then set the shutter speed to the speed that puts the light meter at 0 or a little higher (+1/3 or +2/3). Then you want to zoom your lens out all the way (long focal length reduces the depth of field). Now you need to get fairly close to your subject and get focus. Make sure the subject is not close to the background...it needs some space between it and the background in order to get the blur effect.

In short you want the following...

Wide open aperture
Zoom the lens all the way out (long focal length)
Get close to the subject
Make sure subject is not next to the background

Examples For Understanding Depth Of Field

Understanding Depth Of Field In Photography

[Darth Marty]

On the same subject, please advise me too, I have the anon Eos 1000d and a 18-55mm lens, I too want that shallow depth of field but as far as I can see it the lowest F setting I can get is 5.6, I have used a 70-300mm lens from a friend and even then I can only get it to f4!

How do I get it to f2 which is apparently when you get the best blurry vs sharp contrast, what sort of lens would I need for that?!

Thanks in advance.

[OsmosisStudios]

The 18-55 will actually go down to 3.5 (at 18mm) and 5.6 (at 55mm).

A lens must be built to open up to those apertures: most "consumer" lenses dont. For Canon users there's a sub-$100 (US) lens that is invaluable: the Canon EF 50mm f/1.8. That will get you down to f1.8.

[Samanax]

Originally Posted by Darth Marty

On the same subject, please advise me too, I have the anon Eos 1000d and a 18-55mm lens, I too want that shallow depth of field but as far as I can see it the lowest F setting I can get is 5.6, I have used a 70-300mm lens from a friend and even then I can only get it to f4!

How do I get it to f2 which is apparently when you get the best blurry vs sharp contrast, what sort of lens would I need for that?!

Shallow DOF isn't only dependent on the size of the aperture, there are other factors to consider as well. Read my previous post.