Can photos from a mediocre zoom be made as sharp as a prime lens in post-production?

Question

I use Canon 7D with a 18-135 kit lens. Though the image is in focus, it is not that sharp. I wonder if we can have a sharp image — something equivalent to primes — with post production.

What I have tried:

1. I have manually increased the sharpness in photoshop/lightroom and got a bit of noise here and there. So I do know increasing sharpness gives noise.

2. Increased the sharpness in camera setting.

What I would want in answer: A proper experimented exposure setting which helps me to get an image (in a well lit environment) on which I can increase the sharpness in post production with minimal noise. Resulting in a prime quality image (atleast near.. I do understand its practically impossible but we can at least try it.)

Ask me in comments if you got any doubt and you need me to be still more clear.

Answer 1

The answer to the title question is "well, no." Any post-production that can be done to help a mediocre zoom can also be applied to a prime lens. DxO Optics is raw conversion software that's designed to do exactly that, and while it has more proportionate effect on weaker lenses, even the best get a bit better.

"What I would want in answer: A proper experimented exposure setting which helps me to get an image (in a well lit environment) on which I can increase the sharpness in post production with minimal noise. Resulting in a prime quality image (atleast near.. I do understand its practically impossible but we can at least try it.)"

The key to this is to not stress the lens. Stop the aperture down one or two stops from wide open, and don't depend on the ends of its zoom range. Don't shoot directly into the light if you can avoid it, and don't use a cheap UV filter. Work at the lowest iso setting that will still give you a sharp subject – motion blur is worse than noise – use raw capture to preserve as much information as possible until you can make decisions on a bigger monitor, and consider downloading the free trial of DxO Optics to see if its specialized processing brings you closer to your goal.

Answer 2

There are a few things you can do that make the apparent sharpness go up, though they always come at a cost to the image quality.

You can reduce the size of the image. This allows for multiple pixels to be used to produce one pixel and thus algorithmically the image can be made more sharp based on the level of contrast between the pixels. This trades the total amount of information in the picture for sharpness.

You can also use a sharpening filter. This does basically the same thing, however it tries to produce values for every pixel based on the neighboring pixels. This works up to a point, but it amplifies not just the real edges, but also finds edges that are the result of noise in the image. The image becomes apparently sharper however noise is also increased, so again, the sharpness gained isn't actually identifying smaller details, it is just artificially boosting the edge contrast but is actually less detailed since the impact of noise is increased.

Real lens sharpness on the other hand will produce more image data as it is able to actually resolve detail more clearly. Since this information is not captured with a lens that is less sharp, there is no way to recover this detail in post production because it was never captured in the first place.

Answer 3

That lens is known to be pretty soft. But even the expensive L lenses look pretty soft on a crop camera. On top of that 7D is known to be pretty soft, too, compared to other crop cameras. Digital sharpening (in post on computer or in camera, same thing) is useful and to a raw there should be some degree of it, but it will introduce artifacts that can be visible if you are not careful (dont you just hate tree branches and hairs that are all white and jagged due to this?). The best way is to change viewing size - downscale with a good algorithm (lightroom is very good, and lanczos in software that allows you to choose it). As a rule of thumb you need to resize to at least 50% (gives you a guideline how much you can crop), but in most cases you will be able to resize to 25% for screen. Standard print sizes will give you the same amount of sizing, but if you print to poster/canvas size you might be pushing it. But then you are not supposed to put your nose into it and look for sharpness, but you will stand 2-3 meters away, effectively "resizing" the image with an analogue algorithm.

The trouble is that these sharpening effects only work on the details you managed to catch. Textures gets lost in a soft camera system and they will never come back. The best way for you to catch textures is to magnify the scene as much you can. Fill the sensor , get in close. Dont shoot with intention to crop. Avoid cropping like the plague. Even if most your pics are for screen, shoot with intent to resize (as explained above), that way you maximize textures. The softer the lens, the more you need to "oversample" to get it into the final image, even if it is just a 1 megapixel image in the end. Fill the entire 18MP image with the details and resize it to 1MP yourself (dont let the viewer do it). IF you then get a better lens (like 24-70mm 2.8L II) you can get a bit more freedom, how much magnification you need to get a really good 1MP image, or you can fill the frame to get a rewally good 2-4MP image.

Answer 4

Some things that you would think of to increase the ability to sharpen the image in post processing:

• Use as low ISO setting as possible, to reduce the noise. That allows you to sharpen the image more before the noise gets too visible.

• Add as little sharpening as possible in the camera, you have better options for sharpening in the software.

• Use a lens hood if the light source is not behind you, to reduce light that would lower the contrast in the image.

• Try to find the sweet spot of the lens, where it gives the sharpest images. Usually that is by avoiding the largest and the smallest apertures, and for an all-purpose lens like that it's usually somewhere in the middle of the zoom range.