Depth of field question.....when I use a wide aperture, I still don't get blurriness in the background?

Question

I have a DSR-like camera and really like shallow depth of field shots. Using a wide aperture (aperture priority, f2.8), I took pictures of a row of cars (at a dealership), focused on one and expected the rest further away to be blurry. It didn't come out right....what could have been my problem?

Here are a few links to the pics.
http://i197.photobucket.com/albums/aa165/macatab/MISC/depthoffield2.jpg

http://i197.photobucket.com/albums/aa165/macatab/MISC/depthoffield3.jpg

the one of the rearview mirror was the look i was aiming for..the second one, i wanted the row of cars become blurrier the farther it went out.

i did zoom a little bit on the mirror..

thanks for all your answers...they were all helpful. Focal length and closeness to the subject were the things I was missing. It's been a great lesson for me.

Answer 1

antoni, he has control of zooming though. :-)

The farther you zoom out, the larger the DOF becomes. This is especially the case with non-SLRs because the sensor size is smaller, making the equivalent length of the lens
(in mm) shorter for the same field of view.

So, essentially, to get the shallowest DOF, set the zoom as long as you can. (zoom in) set the aperture as wide as it will go (f/2.8 etc.) and focus as close as you can.

The second shot, assuming your aperture was still 2.8, You probably zoomed out thereby shortening the lens' focal length, you were also probably standing too far away to get the shallow DOF effect.

If you cant get a shallow enough DOF you can post proscess the blur in on photoshop or similar.

Think about these things next time. When it comes to DOF sometimes you are just limited by fate and your equiptment. When using an SLR and a telephoto sometimes I just can't get the DOF big enough without dropping my shutter speed out of hand holding range or blurring my images with diffration.

Thats just how it goes

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Edit:
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It's a trade off then, you'd lose the composition if you zoomed in more, Sometimes you just have to edit it out of camera for the artistic effect, no shame in that =)

Answer 2

It's going to be darn hard to "de-focus" too much using a digital camera while keeping the main subject in sharp focus. The smaller the sensor, the greater depth of field you will have. Generally speaking, the smaller the camera, the smaller the sensor. Your Panasonic DMC FZ8 has the smallest commonly used sensor (1/2.5"). Most of the pictures you take with a digital camera are quite sharp from near to far distances and there is a reason for that which I will explain.

While we speak in terms of the 35 mm equivalency of digital lenses, don't forget that the digital sensors are usually smaller than a full-format 35 mm frame. Most of the more popular point and shoot cameras (including your Panasonic DMC FZ8) have the smaller sensors. It's only about 5 mm wide and 4 mm high. The lens on required to cover that angle of view is an ACTUAL 6-17 mm zoom lens. At these focal lengths, the background is going to almost always be in pretty sharp focus.

In other words, if you WANT to defocus the background, you are going to have to work pretty hard at it. You would have to zoom to the longer end of the lens and set the aperture open as wide as it will go, if your camera even allows you to control the aperture, and get pretty close to your main subject while having the background a fair distance away. Since you have a "superzoom" camera, you have the advantage of some longer focal lenghts available to you.

Put your subjects quite a distance in front of any background that will be visible in your photo. You could use a garden of flowers and stand your subjects 20 yards or so in front of them. As suggested, try the portrait mode to shift things towards a larger aperture, zoom the lens out all the way, and move YOURSELF backwards or forwards in order to frame the picture as you would like it.

This is why the first shot (the chrome mirror housing) worked. You used a much longer focal length in this image than you did for the row of cars. To do the same with the row of cars, you would have to walk about another 30 yards or more away from the point where you were standing and zoomout enough to get the same composition. This would allow you to blur the more distant cars nicely, as you see in the first shot. Another thing that is happening in the first shot is that you have focused on an object that is very close to the camera. The longer the telephoto and the closer the main subject, the more the background will become blurred.

The bigger the sensor, the easier it will be to achieve pleasing bokeh. This means moving to a dSLR, which all have sensors about 20 times bigger than the typical P&S digicam. If you want to really go for brokeh (very bad pun intended), you can get a Canon 5D and you will get exactly the same effect you are accustomed to in a 35 mm camera, since the sensor is the same size as 35 mm film.

Here is an example with a point and shoot camera, although it does have the larger sensor (1/1.8") that makes it easier to blur the background. Even though this is macro mode and f/2.8, where the background should blur the most, it's not terribly blurry because it's relatively close to the subject.

http://www.flickr.com/photos/samfeinstein/872732755/

Here is an example with a point and shoot camera, so it CAN be done. The background is much farther away, though, and this is the larger sensor size.

http://www.flickr.com/photos/samfeinstein/843563558/

Compare that to this image, though, which has a similar subject-to-background distance. The SLR has the obvious advantage.

http://www.flickr.com/photos/samfeinstein/408446616/

Wikipedia does pretty well on the subject of depth of field. See: http://en.wikipedia.org/wiki/Depth_of_field

See also: http://www.photo.net/learn/optics/dofdigital/

Answer 3

You have part of the equation right by deciding to select a large aperture like f2.8. However your missing out on the second part. The reason why you are finding it difficult to blur out the background is because you are using a relatively wide angle lens. the photo of the rearview mirror is shot with a 25.7mm focal length whereas the row of cars is shot with a 15mm focal length. Try using a large focal length lens perhaps around 100mm or greater if your cameras has that ability.

Answer 4

Simply put - if you want the shallowest depth of field for any aperture setting, go to the longest focal-length.

If you zoom back to a wide angle, then you'll get more depth of field.

If you zoom tightly to the telephoto focal length, then you'll get shallower depth of field.

It's the nature of camera lenses. That's why, on cheaper cameras with "fixed focus", the cameras usually have wider than normal standard lenses. That way, everything far and near is in "focus", kinda.

Do this. Zoom out the the maximum and get further away from your subject(s). As you did correctly before, set your camera for aperture priority and use the largest aperture available. You may need a tripod to minimize movement as this will be exaggerated with the longer focal lengths.

I hope this helps.

Answer 5

The "clue" in your question came out near the end, when you mentioned "zoom."

Telephoto lenses will affect the depth of field. f2.8 might not have been a narrow enough setting, considering the distance you may have been from your subjects. And, I recognize the 2.8 may be the smallest aperture you can get with that lens.

If you have a shorter focal length lens, you might get better results.

Answer 6

you have three factors to consider with depth of field

aperture + focal length of lens + distance focused

it is the combination of these factors which determine your depth of field not just one

for the least depth of field largest aperture+long focal length lens+ focus close

Answer 7

with out manual control (in this case focus) you are at the mercy of the camera

if you can manually focus just infrount of the first object, then those in the background will be blurry, if on auto the camera will attempt to get everything sharp even at 2.8...........it will focus in the center of the image

EDIT: note the mirror is in the center of the image.........


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