Testing lens sharpness

I went out to the reservoir the other day to test my lens for maximum sharpness. After I finished I took a few photos with my 28-135mm lens. This was taken at f/11 and I should have used around f/18 from my test results. Anyway, how can I improve otherwise. I know I was off on my focus point in photo #2.

Just as a heads-up: the sweet spot of a lens in terms of what aperture delivers the sharpest image is generally around f/8. The following is a great website to find out information pertinent to your lens: SLRGEAR.

Now if your aim is to reduce light coming into the camera (long exposure during the day, e.g.) or to increase the depth of field (though between f/8 and f/11 is usually enough) then that's another matter.

#1 seems slightly over-sharpened in post-processing to me. But I'm on a non-trustyworthy display device at the moment..

Testing lens sharpness on a landscape at more than f/11 is an exercise in futility for several reasons...DSLR diffraction begins to set in at about f/11 and going higher won't serve any useful purpose. as Chris pointed out.
Additionally, what were you focused on...it takes contrast for the AF mechanism to lock-on and I don't see much, unless it was the far river bank.
A brick wall shot from an angle is still the best way to test a lens/camera sharpness. Take a series of 1000x1000 pixel crops from various places in your image and view them at full size to judge sharpness.

Christopher Steven b wrote in post #14085671
Just as a heads-up: the sweet spot of a lens in terms of what aperture delivers the sharpest image is generally around f/8. The following is a great website to find out information pertinent to your lens: SLRGEAR.

Now if your aim is to reduce light coming into the camera (long exposure during the day, e.g.) or to increase the depth of field (though between f/8 and f/11 is usually enough) then that's another matter.

#1 seems slightly over-sharpened in post-processing to me. But I'm on a non-trustyworthy display device at the moment..

Thanks very much for your comment Christopher and for the info too. I have a friend that's helping me with image clarity and sharpness. I took a series of photos with different f stops then zoomed into a predetermined area to compare sharpness from one f stop to another. My biggest issue seems to have been my focus area and not using the best f stop. Photo # 1 doesn't look over sharpened to me but my eyes aren't as young as they used to be.

chauncey wrote in post #14089938
Testing lens sharpness on a landscape at more than f/11 is an exercise in futility for several reasons...DSLR diffraction begins to set in at about f/11 and going higher won't serve any useful purpose. as Chris pointed out.
Additionally, what were you focused on...it takes contrast for the AF mechanism to lock-on and I don't see much, unless it was the far river bank.
A brick wall shot from an angle is still the best way to test a lens/camera sharpness. Take a series of 1000x1000 pixel crops from various places in your image and view them at full size to judge sharpness.

Thanks so much for taking the time to comment Chauncey. I have heard about diffraction before and also read about the sweet spot for my lens but my friend wanted me to test it myself. I used manual focus and picked out a rock that was 1/3 from the bottom of the frame. I'll try using a brick wall sometime in the near future at your suggestion.

chauncey wrote in post #14089938
Testing lens sharpness on a landscape at more than f/11 is an exercise in futility for several reasons...DSLR diffraction begins to set in at about f/11 and going higher won't serve any useful purpose. as Chris pointed out.
Additionally, what were you focused on...it takes contrast for the AF mechanism to lock-on and I don't see much, unless it was the far river bank.
A brick wall shot from an angle is still the best way to test a lens/camera sharpness. Take a series of 1000x1000 pixel crops from various places in your image and view them at full size to judge sharpness.

Wow, that's great advice, I never test lens sharpness, but I'll absolutely use the brick wall technique if I do; makes perfect sense.

Lonestarlady61 wrote in post #14090784
Thanks so much for taking the time to comment Chauncey. I have heard about diffraction before and also read about the sweet spot for my lens but my friend wanted me to test it myself. I used manual focus and picked out a rock that was 1/3 from the bottom of the frame. I'll try using a brick wall sometime in the near future at your suggestion.

London Headshots wrote in post #14092658
Wow, that's great advice, I never test lens sharpness, but I'll absolutely use the brick wall technique if I do; makes perfect sense.

Stay away from brick walls...there are usually too many issues (crooked bricks, bricks that jut out of the focus plane, is the brick wall perfectly parallel to the sensor, etc) to consider if you're trying to judge sharpness. A brick wall is the worst thing that you can use.

In general, a lens' sweet spot is typically about two stops from wide open.

argyle wrote in post #14096924
Stay away from brick walls...there are usually too many issues (crooked bricks, bricks that jut out of the focus plane, is the brick wall perfectly parallel to the sensor, etc) to consider if you're trying to judge sharpness. A brick wall is the worst thing that you can use.

In general, a lens' sweet spot is typically about two stops from wide open.

Thanks for your reply Argyle. I know your work and it is excellent. So your advice means a lot. I'll stay away from brick walls I used the pump house at the reservoir to see which aperture seemed to be the sharpest. So if my lens is wide open at 3.5 then what would 2 stops down be? I wouldn't think that f/5.6 would be very sharp.

Why wouldn't f/5.6 be very sharp? You should definitely see an improvement over f/3.5. Two fulls stops would be f/7.1

Using the brick wall shot at an angle can give you some very helpful feedback. It will allow you to see not only changes in sharpness, but also changes in the depth of field. That said, finding a compelling subject is far more beneficial to improving your photography. Even a soft image of an interesting subject is far more interesting than a razor sharp image of nothing.

I took a play with your vertical shot. The original looked a bit underexposed in the foreground...bumped up the foreground rocks a bit (just under one stop) and added a little contrast. These are difficult conditions in which to judge sharpness...underexpos​ure due to foreground/sky lighting variance, atmospheric particulate/dust in the distance, possible filter issues if you happened to be using a so-so filter, etc. Taking these conditions into account, the image seems as sharp as can be expected. If you're going to test a lens for sharpness, you really need to be doing it under ideal conditions.

As far as diffraction goes...don't lose a lot of sleep over it. I have plenty of shots taken at f/22 taken hyperfocally that are sharp from front to back. Is it a concern? Theoretically speaking...possibly, but I honestly think that too much is made of it. Granted, a lot depends on the lens' characteristics but if you need the shot and f/16 or smaller is needed, by all means take the shot at the small aperture. Just be sure to nail the exposure/focus (expose to the right).

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Try not to get too caught up in the "sharpness" and "pixel peeping" mindset, as well as the "focusing one-third in" (it doesn't always work). Another consideration that will affect sharpness is "noise", which can be caused by both overexposure and underexposure. Also, what is your sharpening method? How much is applied and when its applied will have a lot to do with the final look of an image.

When doing edits, I'll usually make them at 50% magnification. To check how things look, I'll zoom out to 25% magnification (25% will approximate what you'll see in a print and would be a good indicator to use). Also, when you have close foreground elements in the frame (such as the rocks in your examples), shooting hyperfocally will be a better option.

Instead of overall sharpening the final image, this should be done in stages during the PP process. Generally, after making initial adjustments in LR (exposure, WB), I'll import into PS for the remainder of the work. My first step in sharpening is to apply a mild "capture sharpen" to counteract the AA filter. Then, if certain areas of the image need a tweak, I'll do a "creative sharpening" adjustment (if not, I'll skip this part). Final sharpening, known as "output sharpening", should not be performed until (1) the image has been set to its final dimensions (whether you resize or not) and (2) is based on the image destination (print, type of print method, web publishing, etc). How it will be used will determine the sharpening amount.

This sounds like a lot to take in, but there's a plug-in called "Photokit Sharpener" that already has these various sharpening algorithms pre-set. Its very simple to use, and is also somewhat inexpensive. First thing, though, is to make sure that you have a properly exposed image to start with.

Also, as I mentioned above, with shots that include distant objects as you have here, you're also contending with atmospheric elements such as airborne dust and moisture that will reduce contrast and sharpness...not a whole lot that you can about this (a CPL can only do so much). Bottom line is...be mindful of the conditions that you are shooting in.

Woolburr wrote in post #14098402
Why wouldn't f/5.6 be very sharp? You should definitely see an improvement over f/3.5. Two fulls stops would be f/7.1

Using the brick wall shot at an angle can give you some very helpful feedback. It will allow you to see not only changes in sharpness, but also changes in the depth of field. That said, finding a compelling subject is far more beneficial to improving your photography. Even a soft image of an interesting subject is far more interesting than a razor sharp image of nothing.

Thanks again Woolburr. I guess that I'm having a little trouble understanding why a smaller aperture isn't sharper. What is the purpose of having f/22-f/32 then? From what I've seen from my earlier test f/11-f/14 works better for landscape mode and f/16-f/18 works better in portrait mode. I do intend to find something with lots of detail to test sharpness again and also look for more compelling landscapes to shoot.

argyle wrote in post #14099118
I took a play with your vertical shot. The original looked a bit underexposed in the foreground...bumped up the foreground rocks a bit (just under one stop) and added a little contrast. These are difficult conditions in which to judge sharpness...underexpos​ure due to foreground/sky lighting variance, atmospheric particulate/dust in the distance, possible filter issues if you happened to be using a so-so filter, etc. Taking these conditions into account, the image seems as sharp as can be expected. If you're going to test a lens for sharpness, you really need to be doing it under ideal conditions.

As far as diffraction goes...don't lose a lot of sleep over it. I have plenty of shots taken at f/22 taken hyperfocally that are sharp from front to back. Is it a concern? Theoretically speaking...possibly, but I honestly think that too much is made of it. Granted, a lot depends on the lens' characteristics but if you need the shot and f/16 or smaller is needed, by all means take the shot at the small aperture. Just be sure to nail the exposure/focus (expose to the right).

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Thanks for taking the time to edit my photo Argyle. I like the results! I'm starting to understand just how much dust, airborne particles etc...can effect my photos. I also need to invest in a higher quality CPL filter. Any suggestions? I have the Cokin GND filter kit and use that for later in the evening or when there is high contrast areas in my photos.

Hi,

Get yourself a copy of this:
http://www.amazon.co.u​k …TF8&qid=1332853​949&sr=8-1

I have read it and after a while it all starts to make sense about f stops etc.

Lonestarlady61 wrote in post #14113230
Thanks again Woolburr. I guess that I'm having a little trouble understanding why a smaller aperture isn't sharper. What is the purpose of having f/22-f/32 then? From what I've seen from my earlier test f/11-f/14 works better for landscape mode and f/16-f/18 works better in portrait mode. I do intend to find something with lots of detail to test sharpness again and also look for more compelling landscapes to shoot.

Once you get to a certain point with the aperture, you introduce a new problem....diffraction​. With many lenses, f/16 is the breaking point, although some lenses begin showing the effects at f/11. Tiny apertures will give you more depth of field, but at the expense of image quality/sharpness.