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Old Sep 28, 2006, 4:14 PM   #1
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[align=left]Professional, commercial photographer = background. 12 years teaching Digital Photography
and Adobe Photoshop. Multiple camera models used.

The Canon 20D 8.3 megapixel model I use as my current high-end camera has concerned me on many occasions with poor focusing results. I have always blamed myself. However, I have now been using this camera for 13 months, and have come to expect acuity/clarity issues under many different circumstances. I am beginning to suspect the camera.

I photograph for regional lifestyle magazines, and must produce very high-quality, 'slick' photos. Subsequently, I am quite aware of everything which happens through the viewfinder. Yesterday I climbed over 8,000' up Mt. Rainier's south flank to photograph the receding glaciers. I had (2) lenses to work with, my standard 17-85mm and a 70-300mm Canon longrange. I was very carerful to perform exposure compensation in my snow | glacier shots. I also was exceptionally mindful of AF points selected, and did not snap the shutter until I had one or more on my desired distance/subject.

Despite this, nearly 15% of my photos, especially the longrange shots, suffered badly from soft focus or forward focus. This has now aggravated me to the point where I need to know if it IS the camera. Can anyone share similar experiences with me, or perhaps point me to a definitive source online where this very topic might be highlighted? Thank you.
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Old Sep 28, 2006, 7:18 PM   #2
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It's hard to say what the problem is from your description.

What some people interpret as "front focus" is sometimes because the portions of the image closer to the camera have more pixels representing them, because they occupy a greater percentage of the frame. So, you'll see more detail in closer portions.

In other words, it may not have anything to do with focus or depth of field.

You don't have unlimited resolution, and with landscapes, fine detail that is represented by very few pixels because of the small percentage of the frame occupied can look less detailed at larger sizes simply because of resolution limitations. So, a tree that's closer may be fine, and one that in the distant background may appear soft at larger viewing sizes, just because of resolution limitations.

If you use a longer lens (or move closer) so that it appears you're using twice as much optical zoom, you'll have 4 times as many pixels representing your subject (because resolution, like area, is computed by multiplying width x height).

Lin Evans has a very good forum post HERE that you may want to read through discussing how the human brain interprets fine detail in an image and how that illusion can be shattered when viewing/printing at larger sizes.

Focus problems do occur. So, that's not to say you don't have an equipment problem. But, if you're shooting landscapes, it's unlikely, since Depth of Field is usually going to be pretty great for those types of shots.

Were you trying to focus on something closer than infinity, using a Hyperfocal Distance focus point to get more of a scene in focus? If so, perhaps your calculations were off. There is a pretty good Depth of Field calculator at this link (make sure to select your camera model before plugging in a focus distance, focal length and aperture):

http://www.dofmaster.com/dofjs.html

If they're just soft, perhaps you have a lens issue. For example, you're stopping down the aperture too much.

Most lenses are going to be sharpest 2 or 3 stops down from wide open, and most lenses tend to gradually start getting softer once you stop down to much more than around f/11 or so. If you try to go down to very small apertures (for example, f/22), that usually does more harm than good and gives you softer images due to defraction, unless you really need that much DOF for something like macros.

You could also have a shutter speed issue, causing motion blur from camera shake if not using a tripod and cable release, especially at longer focal lengths (I see you mentioned using a 75-300mm lens, too).

If you were not using a tripod, it would be a good idea to make sure your shutter speed was 50% faster than the reciprocal of the focal length using a DSLR with an APS-C size sensor.

For example, if shooting at max zoom a 300mm lens, the traditional "rule of thumb" is that shutter speeds should be 1/300 second or faster to prevent blur from camera shake.

But, because of angle of view differences from a smaller sensor (your lenses will have narrower angle of view/more apparent magnification compared to the same focal length lens on a 35 camera), it's a good idea to go about 50 or 60% faster.

So, I'd try to keep shutter speeds at around 1/500 second at the long end of a lens like your 75-300mm if you are not using a tripod. Otherwise, you're going to risk softer photos due to camera shake if you're not very careful.

Also, most 75-300mm zooms are not the highest quality anyway. Canon's models in this focal range look like they're a bit softer on their longer end compared to their wider end.

http://old.photodo.com/prod/lens/det...-56II-99.shtml

If you were using a tripod and shutter speeds were very slow, you could even be seeing blur from wind in foilage.

And yes, you could have an Autofocus issue. There are a number of failure points that can cause Autofocus Errors (AF Sensor Alignment, Mirror Alignment, etc., and even a lens can be at fault).

Sometimes reflective surfaces (and you mentioned snow) can fool an Autofocus System, too.

There are numerous focus tests you can find "around the net" to see if you could have an equipment issue. Here is one example:

http://photo.net/learn/focustest/

But, I'd probably post an example including the EXIF info that members can look at to see if a camera setting could be causing the issue. If using Photoshop for downsizing, make sure to use "Save As" versus "Save for Web". Otherwise, it will strip out the EXIF. It's a good idea to downsize images to around 640 pixels wide for attaching to forum posts here, and you'll need to make sure the filesize is under about 250,000 bytes.

Illustrated Guide to Posting Images

Or, better yet, post a link to a full size image if you have a web site somewhere that hosts them for you (versus trying to display an image within a forum post, where we may not be able to see enough detail to see what you're referring to with a smaller image).

If you don't already have some web space for this purpose, you can open a trial account at http://www.pbase.com that will give you 10MB of space (enough to post a photo or two).

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Old Sep 28, 2006, 7:24 PM   #3
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P.S.

I moved this thread to our Canon DSLR Forum, where you'll find lots of Canon DSLR owners that may be able to help you get to the bottom of your problem.


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Old Sep 28, 2006, 7:28 PM   #4
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[align=left]Thank you. I believe you may have hit on it with the shutter speed setting and hand-held shots
with the 70mm-300mm lens. This was my first experience using this lens, and I purposelly
left the tripod behind that day because of the grueling climb up Mt. Rainier I knew I faced.
I tried my best to brace the camera, sometimes using a rock, sometimes sitting and using my
knees, but I don't believe my shutter speeds were fast enough, ,and this probably accounts
for the soft quality.

I appreciate this insight. Thank you very much.
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Old Sep 28, 2006, 7:38 PM   #5
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Hopefully, that's the only issue.

More often than not, blur from camera shake is the culprit when someone suspects a focus problem (and camera shake is magnified as focal lengths get longer).

If you check the EXIF for the shutter speed used, and find that the blurry images were using a shutter speed much slower than around 1/focal length, that would be the most likely suspect for the cause of your softer images.

So, if you can't use a tripod, it's a good idea to use a bit higher ISO speed to keep shutter speeds up if you must stop down the aperture. Sometimes, a bit of noise/grain can be preferable to blur.


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Old Sep 28, 2006, 7:49 PM   #6
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P.S.

I forgot the most important thing, since I see this is your first post here.

Welcome to the Forums!


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Old Oct 24, 2006, 9:58 AM   #7
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Thanks for bringing up this problem I have been a loyal canon user since 1974. Havingnow had problems with soft focus on the 10 D and 20 D I am questioning that loyalty.

My problems like yours have occured at long focus distances using the 28-135 mm lense and the 75-300.

How many generations of the D series does it take to makeone that will focus as well and reliablyasthe Panasonic FZ30?

While there are certainly features I will miss, as I do not make my living by photography, Ican and amseriously consideringselling all my Canon gear in favor of keeping up with the advances in the prosumer digitals. I am wearyfrom dissapointing outcomes from once in a life time vacation photos.

Lenses used include 7Canon 75-300 4-5.6 IS,28-135 3.5-5.6, 50mm 1.2 and Sigma17-35mm 2.8-4.



Thanks for any responses.



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Old Oct 24, 2006, 1:11 PM   #8
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I see this thread is about a month old, but I will toss my 2 cents worth in anyway. You didn't mention if you were shooting in RAW or Jpeg. A RAW image will tend to look softer than a jpeg image. But this is to allow more latitude in post processing with the RAW file. You can go into your parameters and set a custom parameter to do more in camera sharping if you like also. Parameter 1 on the 20D has the sharping, contrast and saturation bumped up. Parameter 2 which is the defalt setting on the 20D does not have any addition contrast, sharping or saturation which will result in a softer picture. But if the picture is not in focus, no amount of sharping is going to bring it into focus.
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