topic Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier in Gear Guide

Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

Brandi7dm2 — Wed, 10 Dec 2025 20:05:58 GMT

Hi there, I photograph birds in flight. Currently I am using the canon EF 70-200 1:2.8 L IS USM. I would like to be able to extend my reach, so I am considering the canon EF 100-400mm f/4.5-5.6L IS II USM. My question to you is which is better- to buy the 100-400 lens, or to use a 1.4 magnifier on the 200mm? What are the pros and cons? Thank you.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

deebatman316 — Wed, 10 Dec 2025 20:27:21 GMT

I don’t recommend using teleconverters. For 1 if you use a 1.4x teleconverter you loose 1 stop of light so you go from F/2.8 to F/4. With a 2x Teleconverter you loose 2 stops of light going from F/2.8 to F/5.6. Then the optical quality goes down due to extra glass in the light path. Also the camera and lens’ AF speed slows down. Due to the less amount of light and contrast. Also depending on the DSLR camera being used the amount of AF points that can be used. May be limited to certain AF points or AF may NOT function at all. Also the camera may not be able to achieve AF. Especially older cameras with less AF points. Some cameras have a list of “Lens Groups” that mention different lens and teleconverter combinations. Also IS may work in a degraded form or not at all depending on the camera being used. Canon has had IS since 1995. Certain Teleconverter combinations and lenses may cause IS not to work. But IS will function on older cameras just fine without the teleconverter. Please let us know what camera you have. If it’s an APS-C camera the focal length multiplier of 1.6x will apply. Adding a teleconverter on top of that will make the angle of view even more narrower. Thus making the focal length even longer.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

stevet1 — Wed, 10 Dec 2025 21:35:22 GMT

Brandi7dm2,

From what I've read, the 100-400 is an excellent lens.

Steve Thomas

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

johnrmoyer — Wed, 10 Dec 2025 23:04:00 GMT

You do not say which camera you have. In addition to the downsides mentioned by @deebatman316 , You might get small aperture diffraction blur. If you use Canon DPP software, it knows about the extenders and "digital lens optimizer" will correct small aperture diffraction blur so long as there was enough light to avoid noise. If using Rawtherapee free software, the small aperture diffraction blur is corrected in "capture sharpening".

I use EF100-400mm f/4.5-5.6L IS II USM with extenders frequently and for me it is a less expensive way to get 560mm or 800mm focal length without an expensive long lens.

On my EOS 80D I used EF100-400mm f/4.5-5.6L IS II USM +1.4x III which meant that only the center autofocus point worked really well and birds in flight were still often too far away. In live view mode, autofocus will work no matter the FNumber.

Bald Eagle (Haliaeetus leucocephalus) at Lake Thunderbird State Park in Oklahoma, November 25, 2020

F Number	8.0
ISO	200
Shutter Speed Value	1/790
Focal Length	560.0 mm
Focus Distance Upper	inf
Focus Distance Lower	81.91 m
Lens Model	EF100-400mm f/4.5-5.6L IS II USM +1.4x III

With my EOS R5 I often use EF100-400mm f/4.5-5.6L IS II USM +2x III and in good light it works well. With the dual pixel autofocus nearly the entire sensor is used for autofocus.

Sandhill Crane (Antigone canadensis) at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on November 25, 2025

Camera Model Name	Canon EOS R5
Lens Model	EF100-400mm f/4.5-5.6L IS II USM +2x III
Focal Length	800 mm
Exposure Time	1/800
ISO	1000
F Number	13.0
Camera Temperature	26 C
Measured EV	13.88
Measured EV 2	29.5
Focus Distance Upper	114.01 m
Focus Distance Lower	81.91 m

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

TomRamsey — Wed, 10 Dec 2025 23:41:49 GMT

It's pretty simple in my opinion, you will get more reach out of the 100-400 which is what you want, with a TC and 70-200 you'll get 280mm. With the 1.4 you will also lose a stop of light so the 70-200 won't be that much faster.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

shadowsports — Thu, 11 Dec 2025 01:38:22 GMT

Greetings,

What body is this lens going to be paired with?

I think the Sigma 60-600, 150-600c or Tamron 150=600 G2 should be considered.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

shadowsports — Thu, 11 Dec 2025 03:18:45 GMT

If it's a 7DmkII the recommendations I made above would pair well.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

ebiggs1 — Thu, 11 Dec 2025 15:37:03 GMT

I am a big tel-con hater! 😬 I personally never use one,... anymore. Although I have over a half dozen of them collecting dust in my formerly stop bath stained darkroom converted to storage room. However, I will say the 1.4x does seem to work pretty well on the ef 70-200mm f2.8L. It and the ef 300mm f4L which are the only two lenses that I can, even slightly, recommend a tel-con is OK. (boy that was hard to type). You will notice the two samples above from a guy who normally produces outstanding shots are soft.

I will assume you do have a 7D Mk II, a very nice camera BTW, so my best and the best recommendation is the Tamron SP 150-600mm f/5-6.3 Di VC USD G2. Make sure it is the G2 model. My second choice is the Sigma C model of their 150-600mm super zoom.

My personal and favorite lens of this type is the Sigma 150-600mm f/5-6.3 DG DN OS Sports Lens. But it is very heavy and a little more expensive. It is an outstanding lens. The Tamron G2 was not available when I bought the Siggy S.

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

johnrmoyer — Thu, 11 Dec 2025 16:49:16 GMT

"a bit soft"

It is difficult to overcome 100 meters of air with varying densities, insects, dust, and moisture droplets in post processing. Crop from same photo:

Re: Canon ef 100-400 is II usm vs 200mm with 1.4 magnifier

ebiggs1 — Fri, 12 Dec 2025 15:13:12 GMT

John,

Yeah, I hear ya, it's tough but adding a 1.4x tel-con makes it worse and a 2x makes the problems even more challenging.