Have you ever wondered why, when you look through your viewfinder, it looks blurry? Even when the actual photos you take come out sharp?! The good news is that this is a problem we've seen before, and there is usually an easy fix that will help you quickly bring things back into focus.
Adjust your Diopter
Next to your viewfinder, there is small dial with a plus(+) and minus(-) sign next to it. This is called the diopter and it measures the optical power of the lens. In other words, it is almost like putting a set of glasses on your camera to sharpen what your eye sees through the lens.
This will have no effect on your images (obviously, as you've noticed since your images are still turning out nice and sharp). Just simply adjust this so that what you are seeing comes into focus and you can effectively tell what is in focus and what isn't with your eye alone. This is important if you are doing any manual focus with your lens at any point.
The diopter adjustments are not drastic and most likely will not replace any need you have for wearing glasses. The adjustments are just enough to increase the clarity if it seems a little soft when you look through the camera.
As a little side note, if you are using someone else's camera with diopter adjustments, don't be surprised if you start to get a headache. Your eye is not used to the optical adjustment being made by their diopter. It's just like wearing someone's prescription glasses.
It's just dirty
This might seem a little silly, but every now and again, the viewfinder will get dirty. Some people will use a finger to clean out the viewfinder area, leaving a smudge behind in place of any debris that was found.
The best way to clean your viewfinder is to grab a glass cleaning cloth (the ones used for cleaning eye glasses work great) and wipe out the viewfinder. I always buy this one by MagicFiber on Amazon. I tend to buy them in bulk because I always lose them. You can use a liquid if you wish, but you run the risk of the liquid leaving a residue behind and essentially causing the same problem.
Did you know that you can remove the rubber eye guard? This will help you be able to reach in there to clean the viewfinder as well as behind the guard.
More than the eye can see?
If cleaning the viewfinder and adjusting the diopter doesn't fix the blur, please consider the following:
You might need to consider that your eyes might need a stronger prescription to compensate for the blurriness you're seeing. This might not be the solution you want to hear… Paying for eye-care is the last thing many of us wish for since it can be costly. As photographers, we all know how expensive glass can be. 🙂 But it is worth having your eyes checked out, in case this is the issue.
Through the process of elimination, if you have tried all the above solutions and you are still dealing with a blurry viewfinder, you can reasonably deduct that there might be something wrong inside the camera itself. At this point, if your camera is under warranty, you will be able to send it in and have the problem addressed that way. Having gone through the other suggestions above, you will have a leg to stand on when they ask you if you have done anything to correct the blurry viewfinder.