Understanding the Differences Between Canon’s EF and EF-S Lenses

It’s been a while since I posted this article the first time so I thought it time to clear up a little misinformation I’ve seen floating around the web lately.

What is this Field of View Crop Factor (1.6x FOVCF) everyone keeps talking about and how does this affect my lens choices for the Canon DSLR cameras?

As you know the sensor in the new Rebels, EOS 60D and EOS 7D are much smaller than the full frame sensor found in Canon’s high-end DSLRs like the EOS 5D Mark II and 1D Mark IV. The physical focal length is a optical measurement of a lens and does not change just because you mount it on a 1.6x FOVCF camera like the 60D or 7D, but the field of view the lens exhibits certainly does.

For example, if you are looking for a field of view that a 50mm lens provides on a full-frame DSLR body like the 5D Mark II, you’ll probably want a 35mm lens on your 60D since 1.6 x 35mm = 56mm. The lens is still a 35mm lens, but the final image captured by your 60D will only include a crop of the lens’ complete image.

Wildlife photographers really love the benefit of using high crop factor (1.6x) DSLRs like the 60D or 7D since they can achieve tight subject framing from a greater distance or from the same distance with a shorter, less expensive lens. Using an EF 500mm f/4 L IS USM telephoto lens on a 60D yields the same field of view as an 800mm f/4 IS USM lens would on a 5D Mark II.

So where does the EF-S lens fit in this?

Canon developed the EF-S series lenses (the “S” stands for short back focus) with the rear element of the lens closer to the image sensor than on the EF series lenses. They also matched the image circle of these lenses to the APS-C sensor size. This design enables EF-S lenses to be made smaller, lighter and less expensive. A perfect match for their consumer and prosumer grade DSLR cameras.

Comparing Canon's EF and EF-S Lenses

Canon EF-S lenses are designed specifically for the 1.6x FOVCF DSLR bodies but still require the same 1.6x crop factor to be applied as the standard Canon EF Lenses to get the equivalent field of view comparison. Again, this is because the physical focal length of the lens is the same, regardless of which camera it’s mounted on.

The Canon EF-S 10-22mm f/3.5-4.5 USM is a great example of a well designed EF-S series lens. It provides a field of view similar to what Canon’s popular EF 16-35mm f/2.8 L II USM and EF 17-40mm f/4.0 L USM do on a full frame camera like the 5D Mark II.

Understanding Canon’s EF-S Lenses

I’ve been meaning to write this post for over a year now and finally got around to it after reading so much misinformation on the subject.

What is this Field of View Crop Factor (1.6x FOVCF) everyone keeps talking about and how does this affect my lens choices for the 50D?

As you know the sensor in an EOS 50D is much smaller than the full frame sensor in the new EOS 5D Mark II camera. The physical focal length is a optical measurement of a lens and does not change just because you mount it on a 1.6x FOVCF camera like the 50D, but the field of view the lens exhibits certainly does.

For example, if you are looking for a field of view that a 50mm lens provides on a full-frame DSLR body like the 5D Mark II, you’ll probably want a 35mm lens on your 50D since 1.6 x 35mm = 56mm. The lens is still a 35mm lens, but the final image captured by your 50D will only include a crop of the lens’ complete image.

Bird photographers like me really love the benefit of using high crop factor (1.6x) DSLRs like the 50D since we can achieve tight subject framing from a greater distance or from the same distance with a shorter, less expensive lens. Using an EF 500mm f/4 L IS USM telephoto lens on a 50D yields the same field of view as an 800mm f/4 IS USM lens would on a 5D Mark II.

So where does the EF-S lens fit in this?

Canon developed the EF-S series lenses (the “S” stands for short back focus) with the rear element of the lens closer to the image sensor than on the EF series lenses. They also matched the image circle of these lenses to the APS-C sensor size. This design enables EF-S lenses to be made smaller, lighter and less expensive. A perfect match for their consumer and prosumer grade DSLR cameras.

ef_vs_efs

Canon EF-S lenses are designed specifically for the 1.6x FOVCF DSLR bodies but still require the same 1.6x crop factor to be applied as the standard Canon EF Lenses to get the equivalent field of view comparison. Again, this is because the physical focal length of the lens is the same, regardless of which camera it’s mounted on.

The EF-S 10-22mm f/3.5-4.5 USM is a great example of a well designed EF-S series lens. It provides a field of view similar to what Canon’s popular EF 16-35mm f/2.8 L II USM and EF 17-40mm f/4.0 L USM do on a full frame camera like the 5D Mark II.

Shooting with Canon’s Best Walk Around Lens!

Here’s another image to prove just how well the Canon EF-S 17-85mm f/4-5.6 IS USM performs in the real world. This time with no HDR “slight of hand”, just a single hand-held exposure at 85mm, f/ll for 1/45th of a second.

In the past I would have said this exposure (85mm at 1/45th second) would have been impossible without a tripod but the image stabilization in this lens is superb! Will I throw out my main landscape lens (EF 17-40mm f/4 L USM) and tripod? No, but I may not bring them along hiking anymore and the savings in weight alone (bless my aching back) is substantial.

David Ziser was right. This really is an all around great lens!

Bridge Bound for Nowhere

Bridge Bound for Nowhere
Copyright © 2008 Jeff Lynch Photography
Shot taken with a Canon 40D hand-held, EF-S 17-85mm f/4-5.6 IS USM at 85mm, f/11 for 1/45th of a second at ISO 100 on SanDisk digital film. All post capture processing was done in Lightroom 2 and in Photoshop Elements using Nik’s Color Efex Pro filters. Click on the image above for a larger version.

And yes, that is the color of the water slowly flowing down the Colorado river in East Texas.

Canon Instant Lens Rebates

It’s that time of year again and Canon USA has announced their fall instant rebates good from October 19, 2008 till January 17, 2009. More details on Canon’s Current Promotions page.

  • EF-S 10-22mm f/3.5-4.5 USM $50
  • EF-S 17-55 f/2.8 IS USM $70
  • EF-S 18-200mm f/3.5-5.6 IS $50
  • EF-S 60mm f/2.8 Macro USM $30
  • EF 16-35mm f/2.8L II USM $100
  • EF 17-40mm f/4L USM $50
  • EF 24-70mm f/2.8L USM $80
  • EF 70-200mm f/2.8L USM $80
  • EF 70-200mm f/2.8L IS USM $125
  • EF 70-200mm f/4L IS USM $75
  • EF 70-300mm f/4-5.6 IS USM $50
  • EF 100mm f/2.8 Macro USM $35
  • EF 100-400mm f/4.5-5.6L IS USM $100
  • EF 300mm f/4L IS USM $85
  • Extender EF 1.4x II $25
  • Extender EF 2x II $25

My picks in Red.

Common Sense Lens Selection

I’m a big fan of David Ziser’s DigitalProTalk blog, even though I’m not a wedding photographer nor have that much interest in wedding photography. What makes Dave’s blog really stand out for me is his down-to-earth, common sense approach to photography, lighting and photographic gear.

Take his recent review of Canon’s EF-S 17-85mm f/4-5.6 IS USM lens for example. Rather than get bogged down in all the technical details and comparisons between this lens and Canon’s L Series glass, Dave gets right to the heart of the matter. He gives seven great reasons why this lens works so well for him and tops it off with an incredible portrait image he’s taken using this lens hand-held in very low light.

I regularly shoot with an EF 17-40mm f/4L USM lens (Canon’s least expensive L Series wide-angle zoom) tripod-mounted for most of my landscape work, but I’ve been looking for a good “walk around” lens with image stabilization that doesn’t cost a small fortune. I’ve done plenty of research and compared all my Canon and non-Canon options but couldn’t make up my mind until I read Dave’s review.

No matter what anyone says, cost is always a big factor when selecting a lens and the EF-S 17-85mm f/4-5.6 IS USM is a great bargain. This lens uses Canon’s second generation image stabilization and a fast, quiet ring-type USM that provides full time manual focus capability. For a lens costing less than $500 (USD) that’s quite a deal. My lens arrived from Adorama this morning and I’m looking forward to shooting with it at the Wings Over Houston air show next week.