How to fix “pictures not sharp” issue with lens.

I often see people claiming their pictures aren’t coming out sharp enough. It’s amazing how often this ends up being some weird issue and not actually a problem with the lens. For the most part lenses seem to come off the assembly line really sharp these days. So the first way to “fix” your lens sharpness issue is to check that the following items are not the source of your problems.

Aperture related softness

While many lenses are very sharp when stopped down, far fewer are very sharp wide open. For the most part lenses that are sharp wide open were made pretty recently, probably in the last 30 years or so at most. Even in the modern day with the latest lenses from major companies a lot of lenses are going to be ever so slightly soft wide open. Why this is I couldn’t tell you. Suffice to say it just seems to be the way people think about camera lenses.

Because of all that it’s a general rule that if you want “insanely sharp” pictures you’ll need to stop the lens down. This is the first cure, make sure you are taking your pictures stopped down at least one full stop from wide open. If your lens starts at an aperture of f/4, stop it down to at least f/5.6. Most (not all) lens designs will keep getting sharper as you stop down, but you’ll eventually run into an issue doing that. While many lenses would be razor sharp at say f/16, another optical effect is going to prevent the projected image from being sharp and that is diffraction.

IBIS/IS can soften images

While IBIS and IS have improved drastically of late, the tolerances are so high these tools can occasionally induce a small amount of softness. The goal of IBIS and IS isn’t necessarily to keep pictures razor sharp. That would be nice I guess but it’s not how IBIS systems are rated. The goal is to keep pictures USABLE. This is yet another thing to check on in your quest to determine image sharpness. Even the very best IBIS/IS can show the tiniest bit of softness. If you’re just absolutely obsessed with getting a razor sharp image, turn off IBIS, put your camera on a tripod, and then take your picture. It’s the only way to be sure.

High ISO noise reduction can cause image softness

Noise reduction is one of those things that has barely improved in most cameras and in software like Adobe Lightroom. Across the board high levels of noise reduction cause images to appear soft. Look at it this way, noise is essentially a loss of resolution, therefore, noise is a form of image softness. Fine details will be obscured by large amounts of noise in the image, and when the noise is removed what is left behind? Mushy looking pictures. Avoid the very highest ISO settings if you want the sharpest possible pictures.

Monitor’s can induce image softness

Yet another source of image softness can be caused by the computer monitor. A major source of soft looking images can come from screens that employ any type of image scaling. Examples of screens that use image scaling are the iPhone, iPad, all modern cellphones, all modern tablets, 4k or higher laptops, and 4k-8k desktop monitors. Image scaling is displaying content at a different scale than a perfect 1:1, pixel to pixel relationship between the image and the monitor. This is why I do not have a 4k monitor. I have a 2560 x 1440 monitor that has pixels big enough to maintain a 1:1 relationship between the screen and the content. That means that when I zoom in to 100% in Lightroom, the image pixels match up to my monitor perfectly producing a nice crisp looking 100% view.

On the other hand, on a screen that employs image scaling, such as most 4k laptops, when you zoom in to 100% view, the image pixels are displayed across the “real” pixels of the monitor. Similar to the anti-alias filter over the camera sensor the image might then be blurred slightly in order to avoid inducing an interference pattern. It’s just a weird reality of a pixel based system. You can’t view 1 pixel at a size greater than the size of 1 real pixel but in fact that is what many modern screens are attempting to do.

Another issue could be using a non-native resolution on an LCD screen. For the same reason as before, if you try to load a 1920×1080 desktop onto a 2560×1440 LCD screen, the monitor must attempt to make fewer image pixels line up somehow with a non-divisible number of pixels in the monitor. The solution is again to blur the pixels and spread them as evenly as possible across the screen.

If your monitor isn’t right, you can’t see the truth, you need to get your monitor right before acting like 100% pixel view means something to you.

The lens needs to be serviced

Yes, your lens may need to be serviced, in this case there’s really nothing left to do but contact the manufacturer of the lens. I recently had a Canon 16-35mm L mk III roll off my desk and hit the floor in an uninterrupted free fall. I immediately went to test the lens and found that it was showing coma in the center of frame wide open. I had to send it in for repair. Cost me $600 and took two trips to the shop to get it right but it is working as good as new now.

You can pretty much forget about servicing any modern lens yourself. The one thing that is often doable is replacing the front element. That one single repair is usually doable. But if there are issues further down inside the lens, or god forbid the USM motor has failed, you’re pretty much up a creek without a paddle if you try to DIY the repair. Although it would be more like being up a creek with a paddle and no boat, because you’re literally just going to ruin the lens 99 times out of 100.

While you may find that taking it apart and putting it back together isn’t so bad, ensuring that everything still works afterward can be surprisingly difficult. This is because the lens elements are not always simply popped into place like Lego pieces. Sometimes they’re positioned very carefully with a series of shims which adjust various aspects of the alignment. They may also be rotated to specific positions. You will need a tuned optical test bed for every major step of the optical assembly. Each group is assembled and tested individually before being placed into the lens. You won’t know any of the tolerances, and you won’t have a way of testing it. At best a very knowledgeable lens repair person could take a nice sharp copy, carefully take it apart, measure the various groups extensively and use those numbers to perform a repair on a broken lens. But they won’t really know if that lens is center of range or near to out of range, or if some groups are compensating for others. It’s not an impossible puzzle its just a really annoying one. And while doing all this yourself you’ll probably get dust in the lens and a month later that dust will magically stick itself right to the center of an element and annoy you for all time. Don’t say I didn’t warn you!

It’s not always the lens, some cameras are sharper than others

Camera’s are often designed differently with different sensor technologies. Every sensor has a resolution limit, but depending on what optical technologies your camera employs there may be varying degrees of resolution with similar megapixel sensors due to the design.

Final thoughts

As you can see there could be a lot of reasons why your pictures look soft when you view them on your computer at 100% view. In fact, it may be the case that due to your particular monitor or resolution settings it’s not possible to view pictures “razor sharp” at 100% view.

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