Technical "Can I do this?"

[Westy27]

Hi Guys

First post... There is a bucket load of information on this site. Credit to all i guess.

I am researching the ability to put an 2x extender between my Canon 600D and my 55 - 250mm EF-S lens. I understand that the Canon extender will mount my camera body but the lens will not mount the extender. But what if I did this?

Canon 600D -----> 2x Canon Extender -----> Canon EF mount adapter -----> 55 - 250mm EF-S lens

Will that work?

Cheers

Rob

 

[Gavjenks]

What is a "canon EF mount adapter?"
Are you referring to an M-EOS adapter?
If so no, you can't just throw air in between the lens and where it is supposed to be. If you do, you have made yourself a macro tube -- it would probably physically fit, but you wouldn't be able to focus on anything further than about 6 inches in front of the lens, and everything would be super magnified.

Also, incredibly dark, since you're starting with a dark-ish lens, and then taking 2 stops away from it from the teleconverter, and another 1+ stops from the "adapter." Meaning your lens would have a maximum aperture of something like f/16... not terribly useful sounding. Plus autofocus would utterly not work with that little light.

PLUS the optics of the extender aren't designed to be optimized for that craziness anyway. They're supposed to be next to the lens. Putting air in between would probably do something bizarre, like for instance not being able to focus on anything at all, or having crazy distortions.





I believe Sigma or Tamron make teleextenders that are designed to fit normal lenses, not just L lenses. That's what you would want (although always consider the option of just a longer lens)

 

[gsgary]

Dont waist your money there is a reason the 2x will not fit that lens, it is not good enough

Sent from my GT-I9100P using Tapatalk 2

 

[Gavjenks]

Yes even then, your lens may be too slow for a tele-extender. At best you would only be able to use it in very bright sunlight, etc.

 

[bratkinson]

I'm not 'extender savvy', but I recall reading that a 1.4x extender will drop your maximum aperture by 1 full stop, and a 2x extender, by 2 stops. That being the case, your f4.0-5.6 EF-s 55-250 lens becomes f5.6-f8.0 with a 1.4x extender, and f8.0-f11 with a 2x.

What those smaller size max apertures will do is prevent your camera from achieving auto-focus due to insufficient light reaching the focusing sensors. That's probably why Canon limits their extenders to most L lenses with wide maximum apertures.

 

[Gavjenks]

I'm not 'extender savvy', but I recall reading that a 1.4x extender will drop your maximum aperture by 1 full stop, and a 2x extender, by 2 stops. That being the case, your f4.0-5.6 EF-s 55-250 lens becomes f5.6-f8.0 with a 1.4x extender, and f8.0-f11 with a 2x.

What those smaller size max apertures will do is prevent your camera from achieving auto-focus due to insufficient light reaching the focusing sensors. That's probably why Canon limits their extenders to most L lenses with wide maximum apertures.

And then the weird tube he's sticking on it is another stop at least, making it f/11-f/16.
The reason they limit the lenses is for that reason yes.
And on top of large apertures, it also has to be certain exact lenses, because stuff sticks out of the front of the tele extender, and only certain lenses are designed with hollow space in the back to allow that. Other lenses, even if wide enough aperture, will crash into the extender and damage the glass on both when zoomed out.

HOWEVER,
Autofocus totally works just fine up to like f/8 at least, I don't care what they say. Often higher. And in live view mode, it works almost indefinitely, I've autofocused correctly at the darkness equivalent wide open aperture of about f/300 before (as in huge amounts of ND filter at night time)
And in some cases, you may be able to put on other lenses not technically "allowed" but have them fit, IF they are zoomed all the way out. If you look at the back of your lens and zoom it out and it seems like the back moves forward a decent amount, it may be possible. It's an expensive mistake though if you're wrong. Or if you hit something and push the lens back accidentally...

 

[Overread]

Teleconverters work by magnifying the lenses results; because of this if you magnify the results from a weaker lens you will show up far more aberrations and weaknesses in the glass. This results in a much softer photo. A 50-250mm is already going to be getting a touch softer at the 250mm end; doubling it to 500mm is going to be very soft.

The loss of two stops of aperture from the lens also means that you've much less light to work with, which makes getting a good exposure (esp of anything that might be moving and thus requiring a faster shutter speed) much harder. This is even more the case since no lens is sharpest wide open (at its maximum aperture) and as such you'd ideally stop down one stop to get some sharpness back from using the TC - however if you're already at f11 that's taking you even further into tiny apertures and even less light.

I'm not sure what the EF adaptor is that you'd be using here, I know that there are EF mount adaptors for fitting other lenses or old canon FD lenses to canon camera bodies, but they'd have a different mount on the front (ergo an EFs lens wouldn't fit).
The only attachment I know that you could use is an extension tube; however using an extension tube will remove your infinity focus from the lens and the result is that you might only be able to focus a few feet away at best and likely only a few inches away from the lens in most cases (how far varies depending on the lens and the amount of extension tube added).

 

[Westy27]

Thanks for all the information people. I'm just a guy with a very small budget who wants to take longer shots of water sports and wildlife. I don't think the body I have is conducive to taking super long shots...

Cheers

 

[robbins.photo]

Thanks for all the information people. I'm just a guy with a very small budget who wants to take longer shots of water sports and wildlife. I don't think the body I have is conducive to taking super long shots...

Cheers

Well by the time you get done buying the teleconverter and adapters, etc.. have you considered maybe an older telephoto lens?

Tamron AF LD 200 400mm F5 6 Lens for Canon  | eBay

Now granted it's not going to be anywhere near L glass in IQ but if you stop it down a bit, use a good fast shutter speed and maybe clean up the shots a bit in post it might be workable.

I'm not recommending you purchase that particular lens from that seller of course but if you poke around a bit and see if maybe you can find one like it that might do the trick, merely included the link to get you started.

 

[Overread]

There's nothing wrong with the Canon 600D for wildlife. The key problem is the lens. Sadly wildlife is one of the more expensive areas to get into because unless your Steve Irwin good at getting close to wildlife you'll need long lenses- and they sadly cost. There are some cheaper options on the market but a good long reaching lens is where you'll find the quality dramatically improves.

 

[robbins.photo]

There's nothing wrong with the Canon 600D for wildlife. The key problem is the lens. Sadly wildlife is one of the more expensive areas to get into because unless your Steve Irwin good at getting close to wildlife you'll need long lenses- and they sadly cost. There are some cheaper options on the market but a good long reaching lens is where you'll find the quality dramatically improves.

No argument there - if you really want to get serious about shooting wildlife the lenses you really need are going to be expensive, there just aren't a lot of cheap options. But given the nature of the OP's question I got the impression they are trying to do this on a pretty limited budget so I thought I'd suggest that as an option. I can't imagine the results would be worse than trying to slap a 2x teleconvertor on a 250 mm zoom.

 

[Gavjenks]

I'm not sure what the EF adaptor is that you'd be using here

I'm fairly confident he was referring to the EOS lens --> Canon M mirrorless camera adapter.
Which is basically nothing more than an extension tube that happens to be the exact length of the difference between a Canon EOS and a Canon M flange to focal distance.


Yeah I can't think of any budget wildlife lens options.
If you don't mind donut bokeh (which is a really big if), there are some fairly affordable mirror lenses you can buy at around 500mm f/8 fixed. There's also some really ****ty ones, so carefully read reviews if so.

The Rokinon 500mm f/6.3 mirror is probably okay, @$143. They are at least a real lens company i've heard of, not a hamburger packaging place that happens to sell mirror lenses like some of the other bizarre brands probably are.
Even so, though, this is manual focus, and no image stabilization, and no aperture control. In exchange for the cheapness you are getting stone age technology, here (and donut bokeh - i.e. out of focus points of lights look like distracting donuts) You'd need a ROCK SOLID tripod or very nice beanbag for a car door, or similar, and nerves of steel with your fine adjustment manual focus.