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Hey, how’s it going? I’m Andy Jones and this is episode 133 of the Photography  Side Hustle podcast.

This week’s episode comes to you courtesy of a guy I was chatting to in a pet food store. He had a Nikon hanging around his neck and said he was trying to learn how to use it. So I said, he should listen to the Photography Side Hustle podcast. He said he would and then out of the blue, he asked “What is fast glass?” 

Ten minutes later I left the store. If you are that man, I’m sorry I can’t remember your name.

If you think I sound a little different this week it’s because I upgraded my recording equipment. 

Okay so …

What is Fast Glass?

Fast glass is any lens that lets in lots of light and allows the camera to have a fast autofocus system. The term glass refers to any lens.

An example of a fast lens is a 70-200 f/2.8, or an 85 f/1.2. These are constant aperture lenses. 

An example of a slow lens is an 18-55 f/3.5-5.6 or a 100-400 f/5.6-8 these are variable aperture lenses.

Just a quick note here. Constant aperture zoom lenses allow you to use say f/2.8 at any focal length. When you zoom in it stays at the aperture you set it to. Variable aperture lenses change the aperture as you zoom in and out.

The F-number on the side of the lens doesn’t mean that it is the only aperture available. All apertures are available on every lens above the maximum aperture.

Fast lenses are the lenses that professionals use in most cases. I’ll talk more about that later.

Next, let’s go over …


Maximum Aperture

Now the term maximum aperture refers to the widest opening the aperture blades inside the lens can open. If you’re not sure what they are do a Google search for “Aperture Blades” or hold a lens up to a light and you should be able to see them.

When you set the aperture to f/16 the opening is very small, and that doesn’t let much light in. But, when you set the aperture to the lens’s maximum aperture the opening is bigger. 

So let’s say we have a 50mm f/1.4 lens. The maximum aperture for this lens is f/1.4 and it lets lots of light on to the sensor.

Now if we had an 18-55mm f/3.5-5.6 kit lens the maximum aperture would be f/3.5 at 18mm, but at 55mm it would be f/5.6. This lens has a variable aperture.

Light is measured in stops. Each of the 3 settings that we use Aperture, Shutter Speed, and ISO, are divided into stops.

The aperture stops are, 1 – 1.4 – 2 – 2.8 – 4 – 5.6 – 8 – 11 – 16.  Each of these stops starting at f/1 lets in twice as much light as the next stop with a higher number. So each step doubles or halves the amount of light coming through the lens.

There are 4 stops from 1.4 to 5.6 and each step doubles. That means that f/1.4 lets in 16x more light than f/5.6, and that is a massive difference.

Why You Need a Fast Lens

Not every genre of photography needs a fast lens. f/2.8 zoom lenses aren’t needed to shoot landscapes. You can get excellent results using f/4 lenses. Landscape photographers generally use apertures in the f/8 to f/16 range. 

The photographers that need fast lenses are sports, wedding, and portrait shooters. They need to control the depth of field using the aperture setting.

Sports photographers capture fast action and need to use very fast shutter speeds. An aperture of f/2.8 will allow them to do that. If the best they could use was f/5.6, they would have to use a high ISO setting and that would cause the images to be grainy.

Wedding photographers use apertures of 1.2 to 2.8 to get photos in dimly lit churches and reception halls.

Portrait photographers control the depth of field so that the background is out of focus. An aperture of 1.8 to 2.8 will keep the subject in focus and everything else out of focus.

If you presently have an entry-level camera with a kit lens the best thing you can do is buy a fast lens. The step up in quality is massive, even if it’s an inexpensive 50mm 1.8 lens. Being able to take tack-sharp photos in low-light situations, like a dimly lit room will open up a whole new world of creativity.


Why are they so Expensive?

They are expensive because of the technology that is in them. 

Take the latest Canon 70-200 2.8 for example. It has 17 elements in it, that is 17 lenses that change position as you zoom in and out. Some of those elements have a special fluorine coating to give the perfect results. 

A lot of lenses have Image Stabilization built in, so that if you move as you take the photo the lens still captures a sharp image.


The autofocus motors are incredible. The speed they focus on a subject is incredible, it feels almost instant. You will miss far fewer images if the autofocus is of professional quality. 

Ask any sports photographer how important autofocus is. They rely on it.


Today with the advances in technology even some of the variable aperture lenses are excellent. But, you will pay a lot of money for anything that is worth owning. There are a few lenses that won’t break the bank, and those are the f/1.8 prime lenses. The 50mm 1.8 is normally the cheapest, followed by the 24, 35, and 85 1.8 lenses. 

Now you know what fast glass is, you can move forward and get yourself some good lenses.



It’s apology time. Two weeks ago I did an episode on Choosing the right camera body. Well, I just discovered an audio message from Mike Carroll, asking about upgrading his camera body that he sent 2 weeks before that episode. I normally check every week, but I didn’t on this occasion.

So this is his question.

*** AUDIO ***

Okay, so he has a Canon SL3 and wants to upgrade to a full-frame body.

Now you can either stay with a DSLR body or get a mirrorless one. 

If you choose DSLR you have the 6D Mark2 which is 26 MP for $1400 ($1800 CND). The 5D MK4 is amazing but costs $2700 ($3100 CDN).

If you look at mirrorless bodies you have the R8 which is a slightly scaled-down version of the R6 mk2 and is $1000 cheaper. At $1300 ($1800 CDN) it is an awesome camera. 

Right, I’m all waffled out now. 

I’ll put the transcript for this episode up at The links for the products I mentioned in last week’s episode will be there too.

I have just set an account up with “Buy Me a Coffee” so that you can support the show if you are interested. There is a link at

The Facebook group is there if you need questions answered, and if you would like me to check out your portfolio or website you can get in touch through Messenger.

I’ll be back next week, talk to you soon, bye.