Images can seem blurred even when f stop is at F22

[amatula]

I bought the Canon SL1 with the standard 18-55mm IS lens . I am having some issues with focus. I cannot attach the photo to this post to show you.. But here is a description: the bottom section seems a little blurry; in fact the rest of the photo does too (but mainly if I zoom many many times do I notice it). Image Stabilization is turned on. The mountain view snow photo is F22, speed 80 (hand-held) ISO 100. With that F stop, I would expect 100% focus. It was not windy. Even when I do use a tripod and speed is faster (125+) I can have this issue to varying degrees. What could be causing this? I would appreciate any thoughts! I realize without seeing the photos you might not be able to assist me but thought I'd try! Thank you and happy holidays, Annie

[jrhoffman75]

Try the same setup at f/8. At very small f-stops diffraction can cause loss of sharpness. 

A small f-stop gives large depth of field, but not necessarily greater sharpness. 

[ScottyP]

By the bottom you probably mean the foreground in a landscape shot.  This is tough without a photo. 

The point about diffraction at tiny apertures is one possibility.

Another is the sharpness limits of the kit zoom.

Yet another is the slow shutter speed you were using, thereby relying on image stabilization and good technique.  

But you mention a tripod too. Note that an inexpensive tripod can shake. Also even on a good tripod you can impart vibration by pressing the shutter button so setting a 2 second delay or using a remote trigger is best.  Also be sure to DISABLE image stabilization when on tripod or the IS can create blur. 

But it if the foreground is all that is blurry you just do not have as much depth of field as you are expecting. You will never get sharp focus from the tip of the lens to infinity, but you can maximize your DOF by focusing on a point 1/3 of the distance into the scene you want to capture, or you can be more precise and look up the hyper focal distance for the aperture and lens and scene you are shooting. 

See if you can post some sample images and the advice quality will increase. 😉

Good luck. 

[TTMartin]

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@ScottyP wrote:

By the bottom you probably mean the foreground in a landscape shot.  This is tough without a photo. 

The point about diffraction at tiny apertures is one possibility.

Another is the sharpness limits of the kit zoom.

Yet another is the slow shutter speed you were using, thereby relying on image stabilization and good technique.  

But you mention a tripod too. Note that an inexpensive tripod can shake. Also even on a good tripod you can impart vibration by pressing the shutter button so setting a 2 second delay or using a remote trigger is best.  Also be sure to DISABLE image stabilization when on tripod or the IS can create blur. 

But it if the foreground is all that is blurry you just do not have as much depth of field as you are expecting. You will never get sharp focus from the tip of the lens to infinity, but you can maximize your DOF by focusing on a point 1/3 of the distance into the scene you want to capture, or you can be more precise and look up the hyper focal distance for the aperture and lens and scene you are shooting. 

See if you can post some sample images and the advice quality will increase. 😉

Good luck. 

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Very good advice, but, I don't think we can blame the kit lens.

At least in the US the SL1 is sold with the STM version of the EF-S 18-55, That is the second sharpest EF-S lens to the EF-S 17-55 f/2.8 IS. The 18-55 STM is actually as sharp as the often praised 15-85 IS.

[amatula]

Thank you! This is all very helpful.

I just figured out how to post images.:)  Here are two. To note: with both I used an older Sunpack UV filter. Both were hand-held.
Settings were:

Barn: ISO 200  F16  125 Manual mode

Other snow scene ISO 100 F22 80  Manual mode  (wind was not blowing but note that the snow on the bottom of the photo appears blurred)

Metering for both -- center weighed

Picture style: standard

Image quality set to Large/Fine

I have other photos without the filter that have the same issue with not total sharpness throughout the photo.

With all photos I have the camera set to 18 mm

I am thinking of purchasing the 2.8 lens or an 1.8 but just want to be sure I can successfully photograph with this lens first.

Again, I really appreciate the help -- I do not recall these issues with my old Nikon film SLRs; so it is a new learning experience for me!

Annie

]

[TTMartin · Accepted solution]

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@amatula wrote:

Thank you! This is all very helpful.

I just figured out how to post images.:)  Here are two. To note: with both I used an older Sunpack UV filter. Both were hand-held.
Settings were:

Barn: ISO 200  F16  125 Manual mode

Other snow scene ISO 100 F22 80  Manual mode  (wind was not blowing but note that the snow on the bottom of the photo appears blurred)

Metering for both -- center weighed

Picture style: standard

Image quality set to Large/Fine

I have other photos without the filter that have the same issue with not total sharpness throughout the photo.

With all photos I have the camera set to 18 mm

I am thinking of purchasing the 2.8 lens or an 1.8 but just want to be sure I can successfully photograph with this lens first.

Again, I really appreciate the help -- I do not recall these issues with my old Nikon film SLRs; so it is a new learning experience for me!

Annie

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Buying an f/1.8 or f/2.8 lens will do nothing to help your images as the issue is you are using too small of an aperture (too high f/number).

One thing coming from a film camera to an APS-C digital camera that you have to understand is that all of the apertures you are use to using shift by one f/stop. So f/16 on your digital Rebel will give you the same depth of field as using f/22 on a film camera. And the same applies to diffraction so f/22 on your Rebel gives you the same amount of  diffraction as using f/32 on your film camera.

Diffraction sets in early when using an APS-C sesnor. Optimum sharpness with your lens at 18mm is at f/5.6 and the further you stop down past that the more diffraction impacts the photo and the less sharp your image becomes. So it becomes a balancing act between maximum sharpness and adequate depth of field.

At wider angles lenses have a very large depth of field. I would suggest at 18mm you try using f/8. This still gives you a very large depth of field from about 4 ft to infinity, and will reduce diffraction as a factor in your image sharpness. 

You also might want to try using the 'Landscape' picture style as this gives a little more sharpening.

 edit: I would also try to bracket the distance of your focus point until you get more comfortable with the performance of your new gear. (i.e. bracket 5 shots with the focus varying between 5 feet and 1/3 of the way into the photo) Unlike with film this doesn't cost you anything, but, time.

[TTMartin]

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@amatula wrote:

One of the other things that is different with digital photography is that you have substantial latitude in post processing even with JPGs and if you shoot RAW you have even more. The above is with some quick adjustments in Lightroom. A slight exposure adjustment, raising the white point and lowering the black point, adding some clarity and vibrance, and then some sharpening.

[RobertTheFat]

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@TTMartin wrote:

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@amatula wrote:

One of the other things that is different with digital photography is that you have substantial latitude in post processing even with JPGs and if you shoot RAW you have even more. The above is with some quick adjustments in Lightroom. A slight exposure adjustment, raising the white point and lowering the black point, adding some clarity and vibrance, and then some sharpening.

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IOW, you made it stop snowing. Whether that's good or bad depends, I suppose, on your point of view (and possibly on what the original scene actually looked like).

To me the shed looks oversharpened. But maybe that's why I have to wear trifocal glasses.

[TTMartin]

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@RobertTheFat wrote:

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@TTMartin wrote:

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@amatula wrote:

One of the other things that is different with digital photography is that you have substantial latitude in post processing even with JPGs and if you shoot RAW you have even more. The above is with some quick adjustments in Lightroom. A slight exposure adjustment, raising the white point and lowering the black point, adding some clarity and vibrance, and then some sharpening.

---

IOW, you made it stop snowing. Whether that's good or bad depends, I suppose, on your point of view (and possibly on what the original scene actually looked like).

To me the shed looks oversharpened. But maybe that's why I have to wear trifocal glasses.

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Yes, post processing is a very personal thing, especially when it comes to sharpening and noise reduction. 

The point of the photo was to show the OP that the JPG that comes out of the camera is not an end product.

[ebiggs1]

Annie, my daughter-in-law's name, BTW,

This is good advice ....

"But it if the foreground is all that is blurry you just do not have as much depth of field as you are expecting. You will never get sharp focus from the tip of the lens to infinity, but you can maximize your DOF by focusing on a point 1/3 of the distance into the scene you want to capture, or you can be more precise and look up the hyper focal distance for the aperture and lens and scene you are shooting. " 

However, the advice about the aperture size is bogus. Sensor size has a relationship with depth of field (on a crop body), but nothing to do with aperture. The f-ratio is a factor between two parameters of a given lens and is totally independent of sensor size, IE an SL-1.  A lens is a lens is a lens, period.  It can not change once it is manufactured.  It is true that larger format cameras can get away with smaller apertures but the lens is always what it is.

My thoughts are, one, you missed your focus point.  If you want the foreground in focus, you must focus on something in the foreground.  You can then re-compose your shot.  Make sense?  The distance will be in reasonable focus.

And secondly, get rid of the filter.  It is not helping and is hurting. Which does bring us to the last part you must face.  This is likely all the better the kit lens will deliver.  It doesn't need any filter that can diminish its IQ.

A word about lens diffraction limits.  A perfect lens will be perfect wide open.  But we all now that ain't gonna happen!  Right?
Diffraction starts the second the lens is stopped down.  There is diffraction at the first f-stop of any lens.
The problem is most lenses need to be stopped down to improve their other optical faults.   So like most things in life there is no free lunch.  You give to get.  In your case and certainly in most cases you will get the most from your lens at f8.  It seems that f8 is the magic f-stop for most lenses.

A lot of settings that are on a camera are for the, "I need this shot more than I need the utmost in quality", photographer.

 All cameras and lens combo's have their sweet spot when all is in harmony.

About you old Nikon film camera, your DSLR is not going to be as sharp as it was.  Digital isn't quite there yet unless you have top of the line gear.  But one other suggestion that will make your photography better is to use RAW at the highest setting and post process you shots.  You got free software from Canon to do just that.  I urge you to make use of it or buy one of the commerical editors on the market.