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Old Dec 20, 2006, 12:13 AM   #1
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I'm getting mixed results with the kit lens that comes with the Rebel XT. Some shots are sharp and well-focussed. But several of the outdoor shots, with plenty of light came out soft, out of focus and/or washed out. I shot most of these in the Av mode, and they were shot at many different aperture settings, so it's not an issue particular to the extremes. I did use a UV filter and a circular polarizer on top of the UV filter, both made by Quantaray. I can't decide if the issues are related to my skills, the lens or the filters. If it's the filters I can quite easily validate that by removing them and shooting the same scenes, which I might be able to do in a few more days. But I suspect it's not the filters.

Here's an example...
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Old Dec 20, 2006, 12:13 AM   #2
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And another example...

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Old Dec 21, 2006, 6:09 PM   #3
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Really not sure about the first one as it all looks slightly soft (as you mention) with no particular focused point, however the 2nd looks to be due to the focus being near infinity but as the aperture is f5 then this is causing the foreground to be less sharp. As you say some are sharp and some aren't then I would say it is probably not filters. I initially thought that it would be motion due to slowish shutter speeds but these are both high enough. OK so I have not been very helpful, when you shoot do you use multipoint focus or single point? Have you got any examples when you have shot at say f8 or f11 so we can see how they have come out?
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Old Dec 23, 2006, 11:54 PM   #4
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Mark, thanks for your response. I use multi-point focus (or whatever the default on the XT is). Yes, I have a few at smaller apertures (around 9) and they're indeed sharper. But it's quite limiting to go to such small apertures to get decent shots, isn't it?
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Old Dec 24, 2006, 12:12 AM   #5
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All this quantary stuff leaves me wonder.

However, if you want a really sharp shot, consider the following:

- pick a shutter speed of at least 1/125th and that should cancel out a little bit of "unsteady hand" phenomena.

- Pick an aperture of at least F8 or higher.

- Set the ISO (sensitivity) so that you can shoot the above settings and still get a decent exposure (ie bright enough picture).

-- Terry
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Old Dec 24, 2006, 5:26 AM   #6
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Quote:
Mark, thanks for your response. I use multi-point focus (or whatever the default on the XT is). Yes, I have a few at smaller apertures (around 9) and they're indeed sharper. But it's quite limiting to go to such small apertures to get decent shots, isn't it?
OK, we need to go back a couple of steps.

You are confusing depth-of-field with sharpness.

A lens for a SLR camera focuses in one plane only. The area in front and behind that plane gets progressively less sharp as the distance from the plane increases.

Wider apertures make that "sharpness" disappear more quickly.

To be unkind one might say that it's not the fault of the equipment you simply don't understand the fundamentals of this sort of photography. But it is also true that at some point all photographers don't understand the fundamentals, so you just need to learn how these things work.

There are lots of good places to learn about those fundamentals, any decent book on learning photography will help.

Here's a link that might help with the specific issue you are struggling with at the moment.

http://en.wikipedia.org/wiki/Depth_of_field

Examine this picture at the top right of the page and then think about the second picture you posted and your comment.

You could also do yourself a favour and realise that the equipment you own now is better than half of the world's great photographers ever used. If you are not getting good results on prints up to A4 size then it would be reasonable to assume that it is most likely that the problem is behind the camera rather than in front.

There are lots of good reasons to buy better equipment, and if you have the money you don't need any reason at all. One big advantage of having professional grade equipment is that you know for sure it's not the fault of the camera or lens if your pictures aren't any good.

The camera and lenses are only tools, part of any craft is to learn to use your tools to their best effect. It's quite amazing how my lenses seem to get better and better as I practice more with them.
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Old Dec 24, 2006, 6:51 AM   #7
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Peri,

I think you hit the nail on the head regarding sharpness versus depth of field.

However, some of those older photographers actually had pretty good equipment ie. medium format "press" cameras, half plate and full plate camera's etc.

(just busting your chops a little).

Probably the owner of the rebel xt could also up the in camera sharpness a little to give it more that P&S sharpness look.
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Old Dec 24, 2006, 7:16 AM   #8
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In my opinion the poster could have the classic Single-Shot AF vs the AI-Servo AF problem

It does not hurt to check it out... If the camera is set in any of the AI-servo modes and the user press the shutter button too quickly the camera will release the shutter anyway even before focus has been achieved- This is just how the AI modeworks because it set the camera on shutter-priority!

Single-Shot AF on the other hand is focus-priority: The camera will not release unless one of the AF point has lock on something



BTW I agree with peripatetic:
"You could also do yourself a favour and realise that the equipment you own now is better than half of the world's great photographers ever used"


Sadly but true :-)
-> Even the "el cheapo" digital only lenses are now sharper than what most Masters have experienced

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Old Dec 24, 2006, 9:24 AM   #9
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Peripatetic,

I do understand the concept of DoF. I've used Canon's film SLR for years and I can recall very few photos that didn't have obvious focus or shutter speed issues that had issues like this.

In the first photo I can't find any point that's focussed, except perhaps the sky (and even that we won't know for sure). Given that the hill should cover most of the AF points, I'd have expected the camera to focus on at least one of its points, preferably the centre. But that's not the case. So either the camera focussed on the sky or the lens is simply not sharp at wide apertures.

NHL, could you please elaborate on the single shot AF vs AI servo AF problem?
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