So, everyone recommended the 50mm f/1.8 lens because they said this lens is “the best lens and it’s cheap!”. You got the lens and now you are wondering what they were thinking. “This lens in horrible. How is this supposed to be a ‘low light lens’ when all my photos are blurry?” you ask yourself.
Well, I hope to educate you on how best to use this lens and other lenses that have similar characteristics.
What is the 50mm f/1.8?
The 50mm f/1.8 (or its ‘faster‘ sibling, the f/1.4 ) are prime lenses that have been made for a standard in photography for many years and will probably be around for a long time. The term “prime” means it’s not a zoom lens. The lens’ focal length does not change. To “zoom” in and out with this lens, you must physically move forwards or backwards, otherwise known as “sneaker zoom”.
For many years, prime lenses have been of superior image quality (IQ) than their co-habitat zoom lens. This has been true until the last 5 or so years, when zoom IQ has greatly increased. These zoom lenses, such as the Nikon 24-70mm 2.8G, may have caught with the IQ of primes, but nothing can touch the small size and fast ‘speed’ of prime lenses.
Why use the 50mm f/1.8?
When a lens is referred to as a “fast” lens, they are talking about the large aperture of the lens. The large aperture allows more light to enter the front of the lens and then enter the viewfinder / sensor. Since there is more light, the shutter speed will be faster. Hence, a fast lens.
As a fast lens, the 50mm is great for low light. Your friends were right about that… but there is some compromising you need to do with a “low light lens”. This is where the problem lies.
Problem with using the 50 mm lens in low light.
When you understand the problem and know how to control it, this problem turns into a feature and this feature will help you enhance your photos.
So now you know that the large aperture of the 50mm f/1.8 (or f/1.4) lens is great for low light situations. Fantastic! But why are you still getting blurry photos when the shutter is faster? This is because the larger aperture of fast lenses keep less in focus when shooting at the larger aperture (i.e. f/1.8). You know those creative photos where the background (or foreground) is out of focus (OOF)? This is why… one of the few contributing factors that control what is called Depth of Field (DOF). We’ll keep the other factors for another post.
So now you’re indoors with your low light lens and taking photos of children running around at f/1.8 because, you know, that’s what the lens if for. So why are your photos blurry?
Wait, are they blurry or are they out of focus? Here is how to tell:
Blurry photos tend to have been taken with a slow shutter speed which causes blur. Either this blur is your subject moving or camera shake. (I’m assuming your caffeine fix wore off from the morning and this isn’t causing more camera shake.)
A shutter speed value that is too slow to hand hold successfully depends on the sensor size, focal length your lens is at, and how well you can hold the camera still. A standard guideline for a cropped sensor like the Nikon DX or Canon APS-C bodies is 1/(2 x Focal Length). For example, say this is a 50mm 1.8 you have. I would try to shoot 1/100th of a second or faster. Could you use a slower shutter like 1/60 sec? Sure, but it’s now your job to hold help eliminate the camera shake. Also with slower shutter speeds, if your subject is moving fast, they might appear as blurred.
Out of focus photos are those where the plane of focus has fallen outside where you intended. These photos usually have one or more of the following explanations for being out of focus.
- Miss focus – You or the camera didn’t focus on the right subject. Yes, sometimes you can’t blame the equipment. For example, when two people are standing next to each other, there is a space in between them, and your focus point is in the middle. Woops, you just focused on something behind them.
- VERY Shallow DOF – This is where the DOF of focus is so shallow that when you focus on the eyes, the nose, ears, and hair are out of focus. Some people like this sort of shot, but some people will complain the entire face isn’t in focus.
- Moved from Plane of Focus – This is the biggie. The#1 reason this lens, and others, are cursed out loud and sometimes in multiple languages. When focusing on a subject and using a large aperture (lets say f/1.8), the plane of focus is pretty shallow. If the subject moves out of that plane it will be come out of focus. Also, if you move the camera forward or backward, this plane moves with the camera so the subject could become out of focus due to you moving the plane. Example #1 below shows a center film canister that is in focus. You can see the small plane of focus by looking at the small area of carpet that is sharp. If this canister grew legs and moved towards (or away from) the camera, it would leave this plane of focus and become out of focus.
Example #1 – Film @ f/1.8
I hope this tutorial helped you understand fast lenses like the 50mm 1.8. If you have any questions or concerns please leave a comment below or email us at firstname.lastname@example.org.