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canon xsi kit lens softness

A

alpineranger

Senior member
I recently got the canon xsi with the 18-55 and 55-250 kit lenses. While looking at the pictures I have taken so far, I notice that every single picture I have taken is much softer than I would prefer. It doesn't matter what the shot is, even shots taken from a tripod of static objects and other portraiture aren't clear. In comparison to the canon sd870 I also have, the sharpness of the xsi is markedly inferior.

I am wondering if this is a problem endemic to some specific dsl bodies or lenses models or whether I just got a bum unit.
 
could be the demozaicing. the sd870 applies a ton of sharpening after demozaicing while the rebel doesn't apply much if anything by default.
 
I have the same problem too, but I am not sure if it's user error, body problem, or lens problem.
Seattle has been pretty very cloudy lately, so I will take a few shots when it gets sunnier.

Maybe you can try taking three different shots of the same scene (maybe with tripod):

1. With autofocus
2. With manual focus
3. With live screen using both modes

And also post the original images that are soft...
 
manual focus with 1:1 magnified live view should guarantee the best focus that you can get.

I haven't heard of any focus shifting after stopping down issues with the 18-55 kit lenses from any manufacturers.
 
I have an XSI with the 18-55mm IS and 55-250mm IS lenses. Both are very sharp (the 55-250 *extremely so*). Actually, sharper than my 50mm f1.8 is until it's stopped down to 2.8 or so. My copy of the "nifty 250" is even razor sharp at 250mm wide open...

You could try taking a photo with a tripod and the IS off just to see....or if you have a friend have him try your lenses and you try his. I've tried a friend's snazzy L lens and honestly the focusing was quicker and quieter but it wasn't really any sharper than my 55-250.
 
Originally posted by: extra
I have an XSI with the 18-55mm IS and 55-250mm IS lenses. Both are very sharp (the 55-250 *extremely so*). Actually, sharper than my 50mm f1.8 is until it's stopped down to 2.8 or so. My copy of the "nifty 250" is even razor sharp at 250mm wide open...

You could try taking a photo with a tripod and the IS off just to see....or if you have a friend have him try your lenses and you try his. I've tried a friend's snazzy L lens and honestly the focusing was quicker and quieter but it wasn't really any sharper than my 55-250.
Click to expand...

For the 18-55mm IS kit lens, what focal length and f-stop seemed sharpest to you? The picture mode can also be important, since built-in camera sharpness is changed for different modes.

How exactly do you determine if your pictures are sharp? Is it done at 100%, 50%, ???
 
Apples and oranges - the comparison between your SD870 and the xsi.

Canon DSLR's in general - apply MUCH less sharpening than a point and shoot. Here's why - a DSLR user is going to add sharpening in post-processing. A point and shoot user is much less likely to add their own sharpening.

Are you shooting in RAW? If so note that NO sharpening at all is done by the camera in that case. Your P&S likely adds sharpening to the tune of a radius 2.5 pixel 0, 100% USM in photoshop, or more.


Also note that the aperture value is inCREDIBLY more responsive in a dslr - your P&S might "say" f/2.8-f/7.1 but in reality due to the sensor size it's an effective aperture of like f/13-f/64. MUCH more depth of field than you have at a similarly number f/stop on the dslr.

I think the problem is that the OP doesn't understand how to use the camera, isn't compensating for factors such as camera shake, long focal length, low light, etc.

Also note that on a tripod you should have the IS feature OFF (if you have one).


"I am wondering if this is a problem endemic to some specific dsl bodies or lenses models or whether I just got a bum unit. " - Neither - as above its most likely user error.
 
I have been busy so I hadn't gotten time to take some shots for y'all, but now I have something (exif data intact). Unfortunately I didn't have a tripod or the canon p&s with me. here:
http://pics.bbzzdd.com/users/invaliddata/IMG_1068.JPG

I don't shoot in raw because I don't have the patience to process pictures that much (I've been meaning to use the jpeg+raw setting but haven't done so yet).

bobdole - the point about the effective aperture of the p&s being smaller was one I haven't considered, but makes sense.


 
If you aren't going to be doing post processing and you like your pictures over-sharpened (like a point-and-shoot camera), you'll need to set the sharpening on the XSi as high as it will go. I wouldn't personally want it that way since you can't "tune" the shots during processing, but it will give a result closer to a point-and-shoot.


You also might need to adjust the exposure to brighten up the pictures. It's hard to say for sure with just one example, but the picture you posted is too dark for me. Using something other than Spot Metering for a landscape photo will also help since you want the metering balanced throughout the shot instead of just on the center.


Max out the sharpening on the camera and increase the exposure a bit (maybe +1 EV if Parial or Center-Weight metering don't give results you like) and your pictures will look more like this straight out of the camera. Again, this isn't ideal since post-processing is part of the workflow for creating great photos, and I'm sure other people can make additional/better adjustment suggestions, but it's decent when using the SLR as a point-and-shoot.
 
I've actually found that the camera overexposes shots, so I usually use -1/3 to -1 EV compensation, with spot or center weighted metering. With this camera I normally take pictures of people rather than landscapes and left spot metering on by mistake. I'd rather the shots come out a little underexposed as the results come out better if the levels aren't clipping. There are a lot of problems with the picture, but the point was that the lighting was good, the lens was stopped down, and it still feels a bit soft to me (I don't want sharpness just for sharpness sake, with the processing artifacts that go along with it).
 
Exif IFD0

* Camera Make = Canon
* Camera Model = Canon EOS DIGITAL REBEL XSi
* Picture Orientation = normal (1)
* X-Resolution = 72/1 = 72
* Y-Resolution = 72/1 = 72
* X/Y-Resolution Unit = inch (2)
* Last Modified Date/Time = 2009:01:11 15:13:17
* Y/Cb/Cr Positioning (Subsampling) = co-sited / datum point (2)

Exif Sub IFD

* Exposure Time (1 / Shutter Speed) = 1/800 second = 0.00125 second
* Lens F-Number/F-Stop = 10/1 = F10
* Exposure Program = normal program (2)
* ISO Speed Ratings = 200
* Exif Version = 0221
* Original Date/Time = 2009:01:11 15:13:17
* Digitization Date/Time = 2009:01:11 15:13:17
* Components Configuration = 0x01,0x02,0x03,0x00 / YCbCr
* Shutter Speed Value (APEX) = 630784/65536
Shutter Speed (Exposure Time) = 1/789.61 second
* Aperture Value (APEX) = 434176/65536
Aperture = F9.93
* Exposure Bias (EV) = 0/1 = 0
* Metering Mode = spot (3)
* Flash = Flash did not fire, compulsory flash mode
* Focal Length = 250/1 mm = 250 mm
* User Comment Character Code = not defined
* Last Modified Subsecond Time = 31
* Original Subsecond Time = 31
* Digitized Subsecond Time = 31
* FlashPix Version = 0100
* Colour Space = sRGB (1)
* Image Width = 4272 pixels
* Image Height = 2848 pixels
* Focal Plane X-Resolution = 4272000/878 = 4865.6
* Focal Plane Y-Resolution = 2848000/584 = 4876.71
* Focal Plane X/Y-Resolution Unit = inch (2)
* Custom Rendered = normal process (0)
* Exposure Mode = auto exposure (0)
* White Balance = auto (0)
* Scene Capture Type = standard (0)

I snipped out some irrelevant hex in your post because it was making the page too wide.

- Moderator fuzzybabybunny
 
Important bits:

f-stop - f/10
shutter - 1/800
focal length - 250mm

As a dslr user - you are going to have to do some post-processing.

That 55-250 isn't the sharpest lens on the block. It's a consumer lens so this is not too shabby. I also own that lens and I've found it is sharpest (as all dslr or SLR - or barrel-type camera lenses in general) - 1-2 stops down from wide open. Wide-open on this lens is f/4 - so f/8-f/12. Looks like you are right on.

I also see you shot at 1/800 WELL over 1/250 (following the rule - shoot at a shutter speed greater than your focal length.) Looks right on.

I've found the 55-250 is sharpest between 55 - 80 or so mm. It's sharpness decreases rapidly above 100mm - and at 250mm is very soft. This lens is very capable of incredibly sharp pictures, but it is far from L glass. If you want very sharp pictures at long focal lengths you are going to pay for it.

Have a peek at: http://www.flickr.com/photos/d...cs/3195235645/sizes/l/ which was taken at 250mm. I did very little post with this one, just brightened it and corrected WB. This lens can get VERY sharp.

I suspect in that photo you were not focused properly. It looks to be focused to infinity, which can happen if you just focus at the horizon. Longer focal length lenses aren't really designed for large depth of field. The compression effect sort of cancels it out. For very good landscapes that are razor sharp throughout - use a wide angle lens, like your 18-55 at 18MM.

So the 2 things working against you in this:

1. Using a lens at its greatest focal length = reduced sharpness
2. Using a long focal length lens attempting to capture a wide depth of field.

Great job on the basics (aperture and shutter speed correct) - but I think the softness comes from the above 2 factors.

Try this: Take a photo of a clear subject (fire hydrant, car, etc) about 25 feet out. Use f/6.3 or f/7.1 and shutter 1/250 or faster in daylight.

Carefully focus and use focal length 250mm. You should see a very sharp picture.

Now take a landscape at f/8 - it'll be much softer.

In reality you really can't get a good wide depth of field with the 55-250mm.




 
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