I don't understand what these mean Canon EF 100-400mm f/4.5-5.6L IS II USM Lens

[Far-Out-Dude]

I am not sure that I understand how to use these, I got the lens ordered on Saturday and have been reading the manual but these have me perplexed. Could somebody please help me to understand these direction. Thank you very much. This will be my first lens of this quality and for now will be attached to an eos M50 with the Canon Adapter.

[rs-eos · Accepted solution]

I'll let others speak to Infinity Compentation.

For focus range limiting, that can be very useful to increase the speed of auto focus.  e.g. if you know your subjects will always be 3 meters or further away, set the switch 3m - ∞.   This prevents the lens from trying to focus on subjects less than 3 meters away.

If instead, you are taking images of subjects that will sometimes be closer than 3m, then set the switch to FULL.  With the increased flexibility of capturing subjects at all distances (well, the minimum focusing distance will still apply), focusing can be slower since the lens is being instructed to operate on its full range of focusing distances.

[rs-eos · Accepted solution]

I'll let others speak to Infinity Compentation.

For focus range limiting, that can be very useful to increase the speed of auto focus.  e.g. if you know your subjects will always be 3 meters or further away, set the switch 3m - ∞.   This prevents the lens from trying to focus on subjects less than 3 meters away.

If instead, you are taking images of subjects that will sometimes be closer than 3m, then set the switch to FULL.  With the increased flexibility of capturing subjects at all distances (well, the minimum focusing distance will still apply), focusing can be slower since the lens is being instructed to operate on its full range of focusing distances.

[Far-Out-Dude]

Thank you for the reply. I will be taking pictures of wild turkey which will range from 5 yards to 60 yards so if I understand correctly I will want to set it to full?

[rs-eos]

Since they'll be at least 5 yards away (approx 4.5 meters), you can set the switch to 3m - ∞.  That should improve auto-focus speed.

[Far-Out-Dude]

Thank you very much.

[jrhoffman75 · Accepted solution]

From B&H website:

When it comes to Canon’s autofocus lenses, the EF and EF-S lenses feature the focusing motors inside the lens barrels, not driven by the camera body. These internal motors are designed to be lightweight and power-consumption friendly, and do not provide enough torque to drive the traditional manual-focus helicoid mechanism.

Canon utilizes two different systems for manually focusing an autofocus lens: mechanical and electronic. In both cases, the autofocus drive system is disengaged from the focus system. Canon says that, in general, it is possible to incorporate hard stops into this system, but it would add considerably to the manufacturing cost of the lens for a feature with limited benefits.

For decades, the Canon FD and EF lenses have featured a variable infinity setting. Canon has two reasons for this:

Thermal expansion Allowances for infrared photography

Canon is compensating for thermal expansion in its optics, not the lens body. Optical glass and crystal materials, such as fluorite, are known to expand and contract with ambient temperature changes. These changes are not seen with the naked eye, but can cause refraction of the lens surface and, therefore, change the infinity distance. This is more of a factor in longer focal lengths but, as Canon points out, many of today's wide-angle zooms are simply inverted telephoto designs and they can be affected by temperature changes.

[Far-Out-Dude]

I thank you for the reply but to be honest I think I am far more confused after reading that than I was before I read it.

[shadowsports]

I missed the tail end of John's reply above and also responded to the Infinity Compensation Mark question. 📸

The lens elements are comprised of groups.  Variance in movement can exist depending on ambient temperatures.  This is due to expansion and contraction.  When you zoom you are selecting a FL between 100-400mm.  When you manual focus and set the lens focus to infinity, the focus can vary (enough) so that a subject may not be in the sharpest focus the lens is capable of.  The compensation mark allows you to judge what this might be.  However, you should trust your eyes and look through the VF, EVF or LiveView making final micro adjustment to your focus before releasing the shutter.  This lets the lens focus as sharp as possible at infinity.  

[Far-Out-Dude]

Thank you.

[FloridaDrafter]

---

@Far-Out-Dude wrote:

"I am not sure that I understand how to use these, I got the lens ordered on Saturday and have been reading the manual but these have me perplexed. Could somebody please help me to understand these direction. Thank you very much. This will be my first lens of this quality and for now will be attached to an eos M50 with the Canon Adapter."

---

Everyone has given great answers.

As for the distance panel and the Infinity mark (the L laying on its side), IMHO I would just ignore Infinity Compensation as it is simply a reminder that your lens may not be accurate at infinity and you may need to use manual focus to get the subject as sharp as possible, that is what the caution in the gray box is advising. I will also add that the distance (in general) shown is not accurate and just an approximation, unlike lenses from the manual focus days.

I'm not sure if DPP (or any other post editor) will use that info during processing when you have the lens optimizer enabled. But I've found that depth of field (DOF) will compensate for any infinity error, which I understand is quite small to begin with. FYI, I've used this lens on 4 DSLR's and 3 MILC's, so I've used it extensively.

Newton