shooting foreground/background

jokerstone · Aug 18, 2007

hey there

i was just wondering, when shooting photos where u want the backgorund blurred and the subject clear in the foreground what settings need to be enabled on the camera? im using a canon a80

also is there a way IN CAM to make the subject in the foregraound appear in color but the backgorund blurred and in b/w?

thanks

Tolyk · Aug 18, 2007

Aperture priority will solve your first question. Shoot with a shallow depth of field and the background will blur out. The closer you are to the subject the more blurred the background will get. Easier to accomplish with telephoto lenses.

As for the second, not to my knowledge. There are cameras with built-in colour select options, but unless your foreground is one solid colour and nothing in the background is that colour, that wouldn't even help.

JaJaPumBA · Aug 18, 2007

I do the color object and b/w background through photo shop...I use Microsoft digital image 2006 edition, It only cost me about 50 bucks...has most the things you need for basic photo editing....and very easy to learn!!

Iron Flatline · Aug 18, 2007

Every camera has two core features - the aperture and the shutter speed. In order to get a proper image, the sensor or film needs to get the right amount of light on it. The aperture is the size of the hole through which the light travels. The shutter speed determines how long it stays open. The bigger the hole, the less time is required to keep the shutter open.

If you shoot with a big aperture (which is defined by a lower number f-stop, like f/2.8) the less time you'll need to keep the shutter open. A big aperture like this results in a shallow Depth-of-Field, which means that most things in front or behind the subject will be out of focus. If you wanted everything in focus (both near and far) then you'd want to shoot with a smaller aperture (like f/16 or f/22 ~ bigger numbers, weird, I know.)

No you cannot do "Selective Coloring" in the camera. You will need an editing application like Photoshop to do that. It's easy, but no camera can do that.

Tolyk · Aug 18, 2007

The Canon S3 has built in selective colouring actually.. it wasn't nearly as useful as doing it in photoshop though.

PhotoMommy · Nov 13, 2007

i love going over old threads.. you learn soo much

dermit · Nov 13, 2007

What has been said so far is true. But. It is all relative as far as aperture and DOF. If you have tried your widest open aperture and still are not seeing much difference in the DOF here is why...

An aperture number represents a size relative to the actual focal length of the lens. So, for example, if your lens is 100mm then an aperture of f/2 would have a physical size of 50mm (100/2). This is why the smaller numbers are the larger sizes.

Now, when you see a point and shoot like the a80 they list the lens as a 38mm to 114mm (3X zoom) What this actually means is the actual field of view (FOV) is equivalent to a 38mm to 114mm lens. It 'sees' the same amount of an image as the actual 38 to 114 lenses on an SLR camera. It's quite obvious that the a80 does NOT have an actual 114mm lens, it would be far larger than the whole camera body. OK, so what does this mean in terms of aperture. It means that the actual focal length of the lens might be something like 10mm. Now take an f/stop like f/2 and the actual physical size of the opening is 5mm. That would physically be the equivalent size of the opening on a 200mm lens at f/40.... if it even had an f/40! F/40 would give us very, very deep DOF indeed.

So we see that since point and shoot lenses tend to be quite small it only stands to reason that the max aperture will also be very small. It is because of this physical limitation that you will rearely see any images made with these cameras show a shallow DOF. Maybe in the future they might be able to simulate this electronically, or maybe they already do, but for now just keep in mind that you might not be able to get there with that camera.

nikonkev · Nov 13, 2007

dermit said:
What has been said so far is true. But. It is all relative as far as aperture and DOF. If you have tried your widest open aperture and still are not seeing much difference in the DOF here is why...

An aperture number represents a size relative to the actual focal length of the lens. So, for example, if your lens is 100mm then an aperture of f/2 would have a physical size of 50mm (100/2). This is why the smaller numbers are the larger sizes.

Now, when you see a point and shoot like the a80 they list the lens as a 38mm to 114mm (3X zoom) What this actually means is the actual field of view (FOV) is equivalent to a 38mm to 114mm lens. It 'sees' the same amount of an image as the actual 38 to 100 lenses on an SLR camera. It's quite obvious that the a80 does NOT have an actual 114mm lens, it would be far larger than the whole camera body. OK, so what does this mean in terms of aperture. It means that the actual focal length of the lens might be something like 10mm. Now take an f/stop like f/2 and the actual physical size of the opening is 5mm. That would physically be the equivalent size of the opening on a 200mm lens at f/40.... if it even had an f/40! F/40 would give us very, very deep DOF indeed.

So we see that since point and shoot lenses tend to be quite small it only stands to reason that the max aperture will also be very small. It is because of this physical limitation that you will rearely see any images made with these cameras show a shallow DOF. Maybe in the future they might be able to simulate this electronically, or maybe they already do, but for now just keep in mind that you might not be able to get there with that camera.

I didn't know this about point-and-shoot cameras. Hmmm.

dermit · Nov 13, 2007

nikonkev said:
I didn't know this about point-and-shoot cameras. Hmmm.

Most people don't. What you should realize about apertures is that they are designed to represent a fraction of the focal length because this relationship represents a consistant way to transmit light. All lenses at the same f/stop transmit the same amount of light. So if I set up my 5D with a 200mm lens at f/2.8 and you set up an XTi with a 28mm at f/2.8 and we point at the same scene with the same amount of available light and the ISO settings the same then they will both require the same shutter speed to make a proper exposure.

A longer focal length needs a bigger aperture to transmit the same amount of light as a shorter lens and a physically smaller aperture because the light has to travel longer down the dark tube that is the lens.

So, although this works great and all for light transmission it does NOT translate to the same DOF for the same aperture. DOF is defined by focal length and actual physical size of the aperture itself. And since we know that the physical sizes of a 10mm vs a 200mm lens at f/2.8 are no where near the same size it is no surprise that the DOF is also not the same.

The shallow DOF capabilities of an SLR is probably the second most popular reason people jump to an SLR. The number one reason is probably shutter lag.