EF vs EF-S Focal length

Hi,
I'm thinking of getting the Sigma 50-150 for my 40D. Would the 50mm end of the SIgma 50-150 on the 40D equal the same field of view if I had a 50mm prime on a full frame?


Thanks for any help!

Unless I'm misunderstanding the question, no.

50mm on a full frame camera is 50mm regardless of whether it's on a prime or a zoom lens. On a 1.6 crop sensor camera such as the 40d, 50mm is equivalent to 80mm on a full frame camera (50mm x 1.6 = 80mm). Again, it doesn't matter if the 50mm on the 40d comes from a prime or zoom lens. The key is that the camera body is a crop sensor so you have to multiply the 50mm by the crop factor which is 1.6 in this case.

50mm is 50mm is 50mm.

Which camera you put it on will change how much of the 50mm you'll see - a 40D you'll see the middle section and not the edges, a 1D you'll see a bit more of the edges, a full frame camera you'll see all the way out to the full 50mm field of view.

So 50mm will have a narrower field of view on a 40D than on a full frame camera... it'll appear to be wider on a FF camera. Nothing in the lens changes, however.

Dmab wrote in post #6911084
Hi,
I'm thinking of getting the Sigma 50-150 for my 40D. Would the 50mm end of the SIgma 50-150 on the 40D equal the same field of view if I had a 50mm prime on a full frame?

Thanks for any help!

No. It's a telephoto zoom on a 40D. It's a useful range on a 1.6x format camera -- provided that you also have a lens that covers the everyday focal lengths that are usually included in a normal zoom lens. For that you would need a zoom that started at 24mm or wider.

To state it precisely: a given focal length simply has a different Field of View depending upon the size of the format body. 50mm on APS-C has same FOV as 80mm on FF, but 50mm FL is 50mm FL, period.

Wilt wrote in post #6911214
To state it precisely: a given focal length simply has a different Field of View depending upon the size of the format body. 50mm on APS-C has same FOV as 80mm on FF, but 50mm FL is 50mm FL, period.

you are correct, but is it SUCH A BIG deal that people who don't get it no matter how many times you tell them that the 50mm is a 50mm no matter what body its on. But that it will FRAME like a 80mm on FF?

The 50-150mm approximates the framing (FOV) of 80-240mm which is close to the classic 70-200mm range that the 70-200mm's were designed for so long ago in the film era.

The Siggy is probably a decent lens, but I haven't read anything about it. Lately Sigma has been making some good lenses (as long as you get a good copy, their quality controls need to step it up a notch).

-Alan

Dmab wrote in post #6911084
Hi,
I'm thinking of getting the Sigma 50-150 for my 40D. Would the 50mm end of the SIgma 50-150 on the 40D equal the same field of view if I had a 50mm prime on a full frame?

Thanks for any help!

If you're looking for the equal of a 50mm prime on a crop body, there are 3 close approximations (mind you that aren't L-lenses). Canon 28mm f/1.8 (approximates 45mm FOV of FF), Sigma 30 f/1.4 (approximates 48mm FOV of FF), and Canon 35mm f/2 (approximates 56mm of FF).

50mm on crop is going to give you the FOV of an 80mm lens on FF/Film. It will be a short-telephoto/portrait lens.

-Alan

Thanks everyone for the feedback, I get the 50mm = 50mm, etc...

I guess what confuses me is when a lens is designated as "digital only", i.e. the EF-S lens, or Sigma's "DC" designation. They are engineered to take advantage of the smaller sensor, correct? That's why you can't use them on a FF body...

So with that in mind, if I look through the viewfinder of a 40D with the Sigma 50-150 (which is DC designated) at 50mm, would I see the same "image" or field of view as if I were looking through a 5D with a 50mm 1.4?

^No, you wouldn't.

On the 5D, you would see a "true" 50mm because it has a FF sensor.

On you 40D, at 50mm you would see is the FF equivalent of 80mm because of the 1.6x crop factor.

Even if the lens is designated for the smaller sensor?

Dmab wrote in post #6911592
Even if the lens is designated for the smaller sensor?

Lenses designed for smaller sensors typically just have a smaller projected image circle; an EF-S 50mm would be a 50mm with a smaller image circle, not an 80mm lens. Again, 50mm is 50mm is 50mm.

Dmab wrote in post #6911560
Thanks everyone for the feedback, I get the 50mm = 50mm, etc...

I guess what confuses me is when a lens is designated as "digital only", i.e. the EF-S lens, or Sigma's "DC" designation. They are engineered to take advantage of the smaller sensor, correct? That's why you can't use them on a FF body...

So with that in mind, if I look through the viewfinder of a 40D with the Sigma 50-150 (which is DC designated) at 50mm, would I see the same "image" or field of view as if I were looking through a 5D with a 50mm 1.4?

No, even though they don't work on the full frame cameras , they still give you the same field of view as if they would work on FF cameras. like a Sigma DC lens 50mm FOV = 80mm on FF FOV no matter what.
A friend of mine and I got bored and checked it on his Sigma 30mm f/1.4 which I think is a DC lens as well.

It doesn't matter what sensor the lens is designated for.

The crop factor for any given camera will "effectively" change the field-of-view you get with any given lens.

Take a Canon EF 24-70 f/2.8L -> A lens compatible with FF, APS-H, and APS-C sensors.

On a FF sensor @ 24 mm -> you get the 24mm FOV
On an APS-H sensor @ 24mm -> you get the FF equivalent of 31.2mm because of the 1.3x crop factor
On an APS-C sensor @ 24mm -> you get the FF equivalent of 38.4mm because of the 1.6x crop factor

The piece of equipment that will change the effective FOV is the camera because of given crop factors, not the lens.

Edit:

Maybe this picture will help explain.

Lets just say that the image below is taken @ 24mm. The image contained inside the red rectangle is what you would see with @ 24mm with a FF camera. The image contained inside the yellow rectangle is what you would see with your 40D @ 24mm because of the 1.6x crop factor.

Dmab wrote in post #6911560
I guess what confuses me is when a lens is designated as "digital only", i.e. the EF-S lens, or Sigma's "DC" designation. They are engineered to take advantage of the smaller sensor, correct? That's why you can't use them on a FF body...

So with that in mind, if I look through the viewfinder of a 40D with the Sigma 50-150 (which is DC designated) at 50mm, would I see the same "image" or field of view as if I were looking through a 5D with a 50mm 1.4?

The confusion of 'digital only' comes about because that term is used in multiple ways by the manufacturers! Some mean 'for APS-C sensor', while others mean 'designed to emit light rays that are closer to 90 degrees to the sensor surface, to avoid CA' Not sure what Sigma means...gotta read the marketing hype they publish.

[edit] OK, here is the Sigma hype from their web site:

"This ultra-wide zoom lens has a wide angle of view from 102.4 - 63.8 degrees (when Sigma mount is used) and it is exclusive to digital SLR cameras. SLD glass elements effectively compensate color aberration. Aspherical lenses provide maximum correction for distortion and various aberrations; high image quality is displayed throughout the entire zoom range. The HSM equipped models makes fast AF speeds and quiet shooting a reality, and it is also capable of full-time manual focus. It has a minimum focusing distance of 9.4" (24cm) at all focal lengths. It is also equipped with an integral Petal-type hood to block out extraneous light.

Ultra-wide zoom lens
10-20mm F4-5.6 EX DC HSM lens allows enjoyment of super wide-angle photography and it is a very powerful tool for indoor shooting and landscape photography with APS-C size image sensors of digital SLR cameras. Wide angle of view 102.4-63.8 degrees (for Sigma mount) offers the photographer greater freedom of expression.

Most Appropriate Coating for Digital SLR Cameras
The new multi layer lens coating and lens design reduce flare and ghost, which is a common problem with digital cameras and also creates an optimum color balance through the entire zoom range.

The best possible correction of aberrations
Three SLD (Special Low Dispersion) glass elements are employed for effective compensation of color aberration, which is a common problem with super-wide angle lenses. One piece of glass mold and two hybrid aspherical lenses, offer excellent correction for distortion, as well as all types of aberration.

Inner focus system
This lens incorporates an internal focusing system, which eliminates front lens rotation allowing the use of a Petal-type Hood and also minimize fluctuation of aberration caused by focusing system.

HSM (Hyper Sonic Motor)
The HSM equipped models ensure a silent, high-speed AF function as well as full-time manual focusing capability for Sigma, Canon, and Nikon-D mount lenses.

Minimum focusing distance of 9.4" (24cm) at all focal lengths
This lens has a minimum focusing distance of 9.4" (24cm) throughout the entire zoom range.

Sigma 10-20mm F4-5.6 EX DC HSM is awarded TIPA best consumer lens in Europe 2006
Sigma 10-20mm F4-5.6 EX DC HSM super wide-angle zoom lens, exclusively designed for digital SLR, wins "TIPA (Technical Image Press Association) best consumer lens in Europe, 2006" prize. Currently, 31 publications from 12 countries are members of TIPA (Technical Image Press Association) organization and chief editors and technical editors of these publications constitute this organization. Since 1991, TIPA has presented many awards in several sectors, including imaging. TIPA has stated that with a versatile range of wide-angle focal lengths, a good optical performance and a budget price, the Sigma 10-20mm is an excellent investment for owners of DSLRs with APS-C format sensors. Its sharpness remains constant throughout the zoom range, and its compact size makes it an ideal companion for shooting travel, landscapes or architectural photography.

* Vignetting will occur if the lens is used with digital cameras with image sensors larger than APS-C size or 35mm SLR cameras.

Dmab wrote in post #6911560
Thanks everyone for the feedback, I get the 50mm = 50mm, etc...

I guess what confuses me is when a lens is designated as "digital only", i.e. the EF-S lens, or Sigma's "DC" designation. They are engineered to take advantage of the smaller sensor, correct? That's why you can't use them on a FF body...

So with that in mind, if I look through the viewfinder of a 40D with the Sigma 50-150 (which is DC designated) at 50mm, would I see the same "image" or field of view as if I were looking through a 5D with a 50mm 1.4?

No, you would not.

The if they every created an EF-S 50mm it would still be 80mm equivalent FOV of film. EF-S is just a difference in mount which protrudes deeper into the body and mounts only to a 1.6x crop body with a 1.6x crop body's smaller mirror. The Sigma DC lenses (and DI on Tamron, and pretty much ALL Tokina) will mount to any EF-mount body, but their smaller image circle means that on a FF body they will vignette.

In order for them to have a "true" 50mm on crop, they would need to create an EF-S 31.25mm (31.25mm X 1.6 = 50mm). Sigma basically did this with their 30mm f/1.4 DC. If Canon ever released an EF-S 31.25 f/1.4 IS USM, it would be a hot seller. I know I'd buy one, and I refuse to buy "digital" lenses.

-Alan