The Basics of Lenses- Zoom

Before I get into all the complicated stuff about the lenses you need to buy, I need to help you understand what a lens is. Today's topic is

ZOOM

Have you ever zoomed in with your cell phone? When you took the picture did it turn out really bad? Have you ever wondered why?  That is why it's called

Digital Zoom

This is my son's stuffed animal, Pukey. If you look closely his edges look a little weird, this is an effect of digital zoom.  Essentially your phone is taking a picture and then zooming in on a certain point...

The black box is a picture taken without zoom. It has 18,000,000 pixels, the blue square is digital zoom. Lets say it is 1/8 the size of the big picture, that means it has 2,250,000 pixels. 

A few camera companies will ramp up that 2.25MP back up to it 18MP. This is done by interpolating the missing pixels. I don't know if my phone does it and I don't care. I give this advice a lot to my wife and family but DON'T ZOOM WITH YOUR PHONE.

Conclusion Digital zoom=Crappy zoom

Optical Zoom

Now there is a reason you see these huge lenses on cameras. That is because they don't use digital zoom they use optical zoom. Optical zoom  is the same technology that telescopes are based on.  Lenses create magic that make things look closer then they actually are. I use the words magic because this isn't a blog on space you don't really need to know how it works just know it does.

 You might not be able to tell from the picture but I was standing way farther back from Pukey for this picture. 

Optical zoom doesn't take a picture then crop it down to zoom in. The elements (lenses) in your lens move to change light so that an object appears closer, and doesn't loose any of it's clarity.  As far as your camera is concerned you have teleported 50ft forward and you are taking the picture there.

So their is a lot of complicated stuff I could get into about optical zoom.  But there are only a few things that are important

• All lenses, even prime lenses, that "Don't Zoom" Zoom. It is just in their nature to zoom, a prime lens' zoom just can't be changed, it is a fixed zoom.
• "Zoom" lenses are also know as telephoto lenses by people that want to sound smarter. 

Canon Zoom Lens EF 28-70mm 1:2.8 L
These things mean...
Canon = Brand of lens
Zoom = I don't really know why they feel they must tell us that but its a zoom lens
EF = The lens Mount (remember EF can be used on Cropped and Full Frame sensors)
28-70mm = The amount of zoom a lens has 28 is reasonably wide and 70 is not very zoomy. This is not a great lens for sports but it is my go to lenses for weddings and portraits
1:2.8 = Aperture we will get into this more in another blog but 2.8 is the best a zoom lens can get
L= Canon's luxury brand

mm

 Zoom is measuered in mm or milometers. The lower the number, the less zoom, the higher the number the great the zoom.

Now if you remember from previous blog posts the zoom of a lenses is effected by the sensor. So in the case of a 50mm prime lens a cropped lens will not be a true 50mm lens. The zoom factor is usually 1.4x with most crop lenses so the 50mm is actually a 70mm

I would go into the science of why they measure in mm and what that means but I don't think it is relevant...

The lens you want for sports is somewhere around 70-200 mm.

And the lens you want taking pictures of your family where you can get off your butt and move is 18-70mm.

I will make recommendations at a later date with more specific lens suggestions.