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Old Aug 12, 2008, 1:37 AM   #1
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So I have been trying to learn all the new settings and soaking up all the advice I can get from people on here and friends that have experience with slr's...I was playing with the shutter speed (S) mode at a motorcycle race today and Im kinda getting that down, but I was also trying to play with the aperture priority mode to get that blurred background effect. I was told to set it to a low aperture so I set it to the lowest (3.5) but I couldn't get a blurred background, Everything would be in focus...Is there something else I need to do or something different I could try? Maybe I'm just doing it wrong???

Any advice/suggestions?

its the A300 with the kit (18-70) lens.
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Old Aug 12, 2008, 7:23 AM   #2
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An aperture of f/3.5 isn't very large, and the only way to get it with the kit lens is to go wide (use a short focal length) which will make a blurred background hard to see.

To see the effect, you need to use a longer focal length. At the long end of the kit lens (70mm)the maximum aperture is f/5.6. At the minimum focusing distance of 38cm, the depth of field is only 5mm. Anything closer or further away will be out of focus, which will give you the effect I think you want.

So, with the kit lens, keep the focal length long, the aperture large, and the focus close, and you should be able to see the effect of a shallow depth of field.

See http://dofmaster.com/dofjs.htmlfor more info.

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Old Aug 12, 2008, 12:32 PM   #3
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To add to TCav's response:

whether or not you'll be able to see the affect will depend on your subject size as well. For instance if it's a full size adult person by the time you get the entire person in the frame - you will no longer have a blurred background. But if you took a picture of something much smaller at 70mm and 5.6 you could absolutely have a blurred background.

In general if you set to max aperture and use longest focal length (70mm) - if you set your distance to your subject such that your subject is filling the entire frame (assuming of course you're beyond minimum focus distance - i.e. this wouldn't work for a fly for instance) you'll get the maximum affect your equipment can produce.

Now - having said that, there is one other aspect to consder - how much distance there is between the subject and the background. If your depth-of-field (DOF) is 10 feet and the background is a wall. If the wall is 5 feet away it will be pretty much in focus. If the wall is 100 feet away it will NOT be in focus. So, even though your equipment may not be ideal for shallow-dof work - by changing your position or your subject's position you can get better results.
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Old Aug 12, 2008, 12:48 PM   #4
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Great, thanks both of you, I will play around with that today and see what I come up with.

What lens would be better for this than the kit lens. Are zoom lenses going to work better?
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Old Aug 12, 2008, 1:37 PM   #5
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firstascent wrote:
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What lens would be better for this than the kit lens. Are zoom lenses going to work better?
Actually, the largest aperture available in a zoom lens is f/2.8 (or thereabouts), and that's not great. If you really want to experiment with shallow depths of field, you should get a lens with a larger aperture.

Sony has the 50mm f/1.4, but it's $350! There are a lot of used Minolta 50mm f/1.7 lenses that would be almost as good as the Sony, a lot better than the kit lens, and go for about $100 on eBay or KEH.com.

50mm also happens to be a pretty good focal length on an APS-C dSLRfor portraits too, btw.
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Old Aug 12, 2008, 1:38 PM   #6
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firstascent wrote:
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What lens would be better for this than the kit lens. Are zoom lenses going to work better?
It has nothing to do with whether a lens is zoom or not. Three factors contribute to depth-of-field for a specific camera:

1. Focal length of the lens

2. Aperture value used (and max available aperture is also an attribute of the lens)

3. Distance from you to your subject

So a 200mm 5.6 prime lens and a 70-200mm zoom lens set at 200mm 5.6 would have the same depth-of-field (assuming same distance to subject).

So - assuming the same subject size, and assuming you can fill the frame with your subject there are 2 ways you can DECREASE dof - use longer focal length (forcing you to move back further to keep your subject filling the frame) and/or use a wider aperture (smaller f-number). The dof calculator TCAV linked to can be played with - you can enter different values for focal length, aperture and distance and see what happens to DOF. The TOUGH part is that if you want the same subject in the frame, when you change the focal length you MUST change the distance. That calculator won't tell you what the distance would have to change TO in order to accomplish your goal. So for instance, if your subject is a 6' tall human. The distance to subject to fill the frame with a 50mm lens vs. a 400mm lens is very different. So, while it is easy to say a 200mm 5.6 lens will give you shallower dof than a 50mm 5.6 lens it is NOT so easy to say will a 200mm 5.6 lens taking a shot of that 6' tall human have shallower or deeper dof than a 50mm 1.4 lens without knowing how far away with each lens you have to be to fill the frame with a 6' tall subject.
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Old Aug 12, 2008, 2:17 PM   #7
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There's probably no way you're going to get the impact you want with that kind of lens, shooting something as large a motorcycle, especially if you're not close enough to "fill the frame" well with it.

One technique you see used pretty often for more impact (blurred background), is to use a slower shutter speed and pan with the action.

That way, your panning will help to decrease any blur from subject movement (since the camera is following the moving rider), with the background blurred because shutter speed is too slow to freeze it (since it's going by too fast from your panning).

That will take practice to master (it's difficult to pan with the action and keep your subject sharp at slower shutter speeds). You'd need to practice. ;-)

If you look at some of the racing photos in our Sports & Action Photos forum, you can find some examples of that technique. Here's one thread... If you look at the EXIF for the images (which shows information like shutter speed, aperture and more), a number of those photos were taken at very slow shutter speeds (around 1/30 second). Shutter speeds that slow were accomplished by stopping down the aperture (higher f/stop numbers), and keeping ISO speed set low. Look at the 4th photo down in this thread for a good example of how that can work. The cars wheels are still blurry, as is the background, because the shutter speed was very slow.

http://forums.steves-digicams.com/fo...mp;forum_id=82

The faster you're panning, the better than kind of approach can work (which is why the impact is greater when the subject is moving from left to right across the frame, versus coming at you head on). In most cases, you wouldn't need shutter speeds that slow for the desired impact with a rapidly moving car or motorcycle (around 1/100 or so would probably achieve the desired result, if the bike was moving directly across the frame).


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Old Aug 12, 2008, 2:50 PM   #8
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JimC wrote:
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One technique you see used pretty often for more impact (blurred background), is to use a slower shutter speed and pan with the action.
Case in point:
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Old Aug 13, 2008, 1:06 AM   #9
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as for the blurred background with a moving subject I was working on that while at the races a few days ago, it will definitely take some work. I did get a few good pics although a zoom lens would have helped get some better close shots but I for sure need a lot more work with panning with the subject and getting the subject crisp and clear. most of my shots I was using a shutter speed of 1/250.

JimC, thanks for that link, I really like the 4th photo down as you mentioned and even more the 5th photo down. that is amazing! I would love to take photos like that. like you said, just need practice! Oh and on the link you sent, for that 5th pic down how just the front of the car is clear and the back half is out of focus, is that just how the photographer took the pic and the settings he used? I really like it.

TCav, the 50mm you recommended, that is a "prime" lens right? which basically means it doesn't zoom in or out? sorry, new to a lot of this. Do those take a little more practice to get used to since you can't zoom in/out to get the photo you want?
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Old Aug 13, 2008, 7:09 AM   #10
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firstascent wrote:
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TCav, the 50mm you recommended, that is a "prime" lens right? which basically means it doesn't zoom in or out? sorry, new to a lot of this. Do those take a little more practice to get used to since you can't zoom in/out to get the photo you want?
Yes, that is a fixed focal length, or 'prime', lens. But 'prime' is a term that gets used for different things. For instance, when using a teleconverter, the lens that is attached to the teleconverter is referred to as the 'prime' lens, whether it is a fixed focal length lens or not. So the term 'prime' is inexact and I avoid using it, but it is part of the lexicon for photography. Within the context of your question, a fixed focal length lens is a'prime' lens.

And yes, using one takes a lot of practice with a technique commonly referred to as "zooming with your feet." [suB]:-)[/suB]
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