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Old Jul 4, 2007, 1:22 AM   #1
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Hi everyone,

I'm using an EOS400D at the moment with the f/4-5.6 IS 17-85mm lens. I was taking a few pics of the Harbour Bridge in Sydney at night, using a tripod, enabled the mirror lockup, used the self-timer feature and used a very small aperture (f/22 I think) to get a crisp shot of the bridge. The only catch is I was using ISO200 to keep noise to a minimum, but to my surprise, all the pics were very blurry (seemed like it was out of focus) when I viewed them on my laptop.

Can anyone help? I thought reducing the aperture and increasing the depth of field woud make my image look sharper.
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Old Jul 4, 2007, 4:03 AM   #2
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If you have an example that would help us to try and work out the cause however when you are stopped right down to f22 although you are getting more dof you are also reducing the sharpness of the lens. At all focal lengths this lens gets softer after f11 and when used wider is gets softer after about f8 so f22 is extreme. Assuming you are shooting at 24mm for arguments sake then here are some figures for what will and won't be in focus if say you have focused at 100m.

24mm f22

Subjectdistance

100m

Depthoffield

Nearlimit
1.32m

Farlimit
Infinity

Total
Infinite

Infrontofsubject
98.7m

Behindsubject
Infinite





24mm f11

Subjectdistance
100m

Depthoffield

Nearlimit
2.61m

Farlimit
Infinity

Total
Infinite


Infrontofsubject
97.4m

Behindsubject
Infinite

As you can see that is not going to make much difference at all to your results however in the focus plane however it will mean you are using the lens where it is at about its sharpest.

Also by making the aperture wider you will reduce exposure time as another possibility is that there was some movement for whatever reason (wind is common) making it soft.

Lastly if you used manual focus then you might have gone beyond infinity to a position where the lens just can't focus.

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Old Jul 4, 2007, 9:45 AM   #3
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An example of the picture would help a lot. My guess is that the camera just wasn't able to focus correctly in the dark. Next time maybe try manual focus to make sure that once you get it focused, it stays there (otherwise it might hunt and not focuswhen you take the picture). You can take test shots at shorter speeds and just look at bright lights and see if they are focused or have a halo.

I would agree with Mark1616 that an aperture around f/8 would be better to use. That's usually the average target aperture to get a lens to perform best - at the same time keeping your shutter speed a tad shorter.


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Old Jul 4, 2007, 9:33 PM   #4
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Thanks Mark,

Yes it was quite windy, although I did try to stabilise it with a tripod.

I might have to dig up the RAW image since I deleted the converted TIF file a few days ago (due to extreme disappointment), but I remember that the subject which is the harbour bridge, was approximately 600-800 metres away as it was across the water from where I was, and yes, probably zoomed in somewhere around 24mm or higher to get the whole span of the bridge.

I guess what I was trying to do, is to take a shot of the scenery where the noise is minimal and the waterhas acalm look due to a longer exposure. Is it possible to come up with a nice sharp image despite the longer exposure? Silly me thought minimising the aperture would do this.
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Old Jul 5, 2007, 3:40 AM   #5
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Also, you will get blurry shots if you have the image stabiliser turned on mounted to a tripod.
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Old Jul 5, 2007, 9:45 AM   #6
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TTfoto wrote:
Quote:
Also, you will get blurry shots if you have the image stabiliser turned on mounted to a tripod.
wow, is this really true
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Old Jul 5, 2007, 10:02 AM   #7
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Ok, here is first example but not with the minimum aperture (I did that one later)

ISO100

f/10

20 seconds
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Old Jul 5, 2007, 10:09 AM   #8
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Here is the other one

ISO200

f/22

30 seconds
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Old Jul 5, 2007, 12:37 PM   #9
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hi there
your settings look ok.
I think what is causing that blur effect is a camera movements while taking the photograph. Somehow, you camera is shaking.
How is your tripod......is it really strong to support the weight of your camera?
I used to have the same problem with a lighter tripod....then i used a manfrotto one, same settings, same place and the photos were great.
Just look at the lights in the first photo. they "moved".
Do you have a remote control? Because when you press the shutter the camera starts shaking a little.....maybe after the timer shoots the photo, the camera still be shaking.

Hope it helps...and you understand what i mean. :|
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Old Jul 5, 2007, 1:13 PM   #10
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My guess is the tripod is to blame. What kind are you using? The first shot looks like a definite camera shake situation.
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