topic Re: wide angle converter in EF & RF Lenses

wide angle converter

qqqavi — Thu, 15 Feb 2018 15:07:00 GMT

Hi everyone,

Can anyone recommend me a wide angle converter with decent quality of x0.43 or x0.5x for a canon lens with 52 or 58 filter diameter? I know a lot of them are very soft .

Thank you.

Re: wide angle converter

ebiggs1 — Thu, 15 Feb 2018 16:23:30 GMT

"Can anyone recommend me a wide angle converter with decent quality..."

Simple, quick answer,... NO ! Don't waste your money.

Re: wide angle converter

kvbarkley — Thu, 15 Feb 2018 16:29:22 GMT

Rather than convert your existing lens, it would be much better to get an EF-S 10-18 lens, you can probably get a good deal on a refurbished one:

https://shop.usa.canon.com/shop/en/catalog/ef-s-10-18mm-f45-56-is-stm-refurbished

for $240.

Re: wide angle converter

qqqavi — Thu, 15 Feb 2018 16:44:32 GMT

Let's say I want to convert a 50 mm lens to a 21.5 mm lens (0.43x) and take advantage of the shallow depth of field.

Re: wide angle converter

ebiggs1 — Thu, 15 Feb 2018 16:55:27 GMT

Same answer. Simple, quick ,... NO !

"Don't waste your money."

Re: wide angle converter

qqqavi — Thu, 15 Feb 2018 17:23:10 GMT

ok. Thank you.

Re: wide angle converter

kvbarkley — Thu, 15 Feb 2018 17:55:02 GMT

You can't get a wide DOF with a wide angle lens.

I used a depth of field calculator.

An f/1.8 50 mm lens with a subject at 3 m has a DOF of 2.8 - 3.2 m

An f/1.8 21 mm lens with a subject at 3 m has a DOF of 2.3 to 4.3 m

Even if you got one of those expensive anti-Teleconvertors that *increase* the aperture number with a wider fov, if the resultant 21 mm lens had an f/1.0 aperture, the DOF would still be 2.6 to 3.6 m.

Re: wide angle converter

qqqavi — Thu, 15 Feb 2018 18:13:37 GMT

I think you mean a shallow DOF not "wide".

Correct me if I'm wrong, but I think that by mounting a WA converter in front of a 50 mm lens (let's say at aperture 1.8), I'll get only a wide angle of view not a deep depth of field. Think of an anamorphic lens.

Best.

Re: wide angle converter

kvbarkley — Thu, 15 Feb 2018 19:18:12 GMT

I think you only get that with something like a Metabones Speedbooster*, not a wide-angle attachment.

*But that has to attach between the lens and the body.

Re: wide angle converter

kvbarkley — Thu, 15 Feb 2018 19:19:50 GMT

Maybe you can try something like this:

http://ryanbrenizer.com/2011/05/brenizer-method-instructions/

Re: wide angle converter

ebiggs1 — Thu, 15 Feb 2018 21:30:32 GMT

" An f/1.8 50 mm lens with a subject at 3 m has a DOF of 2.8 - 3.2 m

An f/1.8 21 mm lens with a subject at 3 m has a DOF of 2.3 to 4.3 m"

= 1.6 meter

"I used a depth of field calculator."

Not correctly it seems! Because the DOF is increased with the shorter FL. A 20mm lens at f1.8 and a subject 3 meters away has a DOF of 1.6 meters. A 50mm lens at f1.8 and a subject 3 meters away has a DOF of only .7 meter.

Re: wide angle converter

kvbarkley — Thu, 15 Feb 2018 22:18:52 GMT

I just checked with another DOF calculator:

http://www.dofmaster.com/dofjs.html

For an APS-C at f/1.8 and a subject distance of 3m:

50 mm DOF is .24 (I had .32)

21mm DOF is 1.45 (I had 2.01)

I certainly had the increased DOF at shorter focal lengths* in there, so I am not sure what your beef is.

*Though I misstated it in the text.

Re: wide angle converter

TCampbell — Fri, 16 Feb 2018 02:04:41 GMT

The whole point of an interchangeable lens camera is that you can change the whole lens... and there are many benefits from doing so.

When you put a focal length multiplier/reducer on a lens, you can create a lot of problems. Not least... is that the camera doesn’t know you put this on the front of the lens. It alters the focal ratio of the lens so there’s no free lunch (you no longer get the DoF of a 50mm lens when you put a reducer on it). But since the lens is going to report what it is (and doesn’t know about the focal length reducer/multiplier) it can screw up it’s notion of metering and focus. And of course the optics aren’t optimized for it.

MUCH better idea to get a lens with the focal length and focal ratios you need for the type of photography you want to do. That’s why the lenses are removeable.

Re: wide angle converter

RobertTheFat — Fri, 16 Feb 2018 03:18:42 GMT

@TCampbell wrote:
The whole point of an interchangeable lens camera is that you can change the whole lens... and there are many benefits from doing so.

When you put a focal length multiplier/reducer on a lens, you can create a lot of problems. Not least... is that the camera doesn’t know you put this on the front of the lens. It alters the focal ratio of the lens so there’s no free lunch (you no longer get the DoF of a 50mm lens when you put a reducer on it). But since the lens is going to report what it is (and doesn’t know about the focal length reducer/multiplier) it can screw up it’s notion of metering and focus. And of course the optics aren’t optimized for it.

MUCH better idea to get a lens with the focal length and focal ratios you need for the type of photography you want to do. That’s why the lenses are removeable.

Those adapters are relics of a time when zoom lenses were mediocre and relatively expensive. The adapter was a cheaper alternative that didn't cost you all that much in image quality.

Zoom lenses are still relatively expensive, but now range from good to excellent in quality. Adapters are still a cheaper alternative, but usually cost you dearly in image quality. And as Tim pointed out, the modern symbiotic interactions between camera and lens are not supported by the adapters. (Note that their purveyors are fond of calling the adapters "lenses", but that's really inconsistent with the current meaning of the term.) Tim, Ernie, and others have advised against their use, and that advice is best heeded.

Re: wide angle converter

ebiggs1 — Fri, 16 Feb 2018 15:15:58 GMT

"I certainly had the increased DOF at shorter focal lengths* in there, so I am not sure what your beef is."

There is no "beef" ! I simply reacted to this statement.

"You can't get a wide DOF with a wide angle lens."

Obviously you can. I certainly had no intention to offend you.