Thoughts on the RF 24–240mm F4-6.3 is USM lens

[stromy93]

I've got a Canon EOS r100.  I got the EOS R100 RF-S18-45mm F4.5-6.3 IS STM & RF-S55-210mm F5-7.1 IS STM Lens Kit.  I've been looking at the Canon RF 24–240mm F4-6.3 is USM Lens as a way to not have to carry so many lenses.  I've done some research on the 24-240mm lens and have seen that it's received a lot of mixed reviews on Canon, Best Buy, and Amazon websites.  I want to have a good all-around lens that I can take to the mountains, Grand Canyon, or wherever and snap some good pictures.  But am concerned about some of the distortions and other negative reviews.  Anyone has other feed back that might be helpful.  Is the lens worth spending the amount of money for?

[shadowsports]

Greetings,

Can't say I've heard much negative regarding this lens.  Please confirm you understand what happens when you use a full frame lens on an APS-C based camera.

Tronhard (Trevor) has made a few good posts about his 24-240.  His photography is masterful.

Moody Morning the the R6 & RF 24-240 - Canon Community

Trying out the RF 24-240 on Wildlife with the R5 - Canon Community

Take a look.

[stromy93]

Thanks for the information.

[Tronhard]

Hi and a belated welcome to the forum:

Many thanks and humble appreciation to Rick for his generous description of my work.   Indeed, I am a fan of the RF 24-240 IS USM as a single solution, walk-around lens.
As I understand it, the objective is to have one lens that you don't have to swap in the field.  There are several elements at play here and I shall start off by addressing the lens design itself.

Optical and Computational Lens Corrections:
There have been comments about distortion and vignetting at the wide end of the RF 24-240 range, but these generally came out when the lens was first released, before those reviewers appreciated what was going on 'under the hood', or had not got access to the lens correction software for RAW images that all lenses require.
In order to get such a wide focal range, distortion and vignetting are a common risk, and conventional optical design wisdom would have created an extremely expensive and heavy optic: for example the last such lens from Canon was the EF 28-300L f/3.5-5.6 IS USM (2004) - an all-metal, professional grade lens that was very expensive and heavy - I had one for quite a few years.  It was a gorgeous optic, but it was not cheap and certainly not a travel lens for the average person.

In between times, cellphones have pioneered the use of computational photography: that is, using algorithms to manipulate and enhance the performance of lenses and sensors (initially in cell phones) without building large heavy optics.   It's taken a while, but finally that methodology has come to the lenses of dedicated cameras along with other AI features.  For Canon, it appears in a couple of lenses that I have: the RF 24-240 and the RF 14-35L f/4 super wide angle lens which is a pro-grade and not cheap optic - so as a solution it's not inherently a budget feature.

How it works is this.  The lens captures an image somewhat wider than would be achieved with the advertised minimum focal length (i.e. a wider Field of View)  and to which it makes corrections using computational photography to get rid of the vignette and straighten up the sides, rendering the advertised focal range and a great result.   For JPG images, this is done in-camera, while for RAW images that is automatically applied in post-production software like Photoshop, for example.   Now, one can turn it off to see the uncorrected result, but it is beyond me why anyone would actually want to do so unless to pad out their review material.

I actually did a series of comparison tests, using the full-frame R6 (which is significant) with the RF 24-240 against the RF 24-105L f/4 (pro) lens that I also had.  Looking at the corrected results this is what I got - I deliberately chose an inside (Museum) location for the height and width and straight lines: it was also a good test of the lenses in dim light:
RF 24-240@24mm, f/6.3, 1/80sec, ISO-250 24-105 @ 24mm, f/6.3, 1/60sec, ISO-500 RF 24-240@24mm, f/6.3, 1/4sec, ISO-250 Rf24-105@26mm, f/6.3, 1/15sec, ISO-1600RF 24-240@50mm, f/6.3, 1/2sec, ISO-250 RF 24-105@50mm, f/6.3, 1/15sec, ISO-1600

To me, these compare extremely well, especially considering the difference in focal range, and the fact that the RF 24-105 is a significantly more expensive L-series lens.   However, in your case there is another factor to consider:

Understanding Field of View and Sensor Crop Factor:
Most of the tests I have seen and, in fact, conducted myself, have been using a Full-Frame sensor camera which, because of its larger sensor, captures more of what the lens projects towards it.  Your camera is what is called an APS-C crop-sensor camera, because the sensor is smaller and thus captures a smaller area of the light projected onto it by the lens. 
Your existing lenses are RF-S units, that are specifically designed for crop sensors but will not play nicely with Full-Frame cameras.  The RF 24-240 is designed for Full-Frame units, but work perfectly well on your crop-sensor body, but will not capture the full area that it is potentially capable of when used with a FF sensor. The bottom line here is that it will not be recording anything like the material on the edges where an uncorrected image will be obvious, so you should have not issue at all. 

For a full explanation of how sensor size and focal length correlate, see this article I wrote on the subject. 
Focal Length, Field of View, Shutter Speed, Sensor Size & Equivalence 

I hope this provides the information you need, but if not feel free to come back to me.  If it does, please mark this as a solution.

[stromy93]

Thanks Trevor for the input. The distortions and such was what I was worried about. But sounds like that has been fixed. I use JPG anyway. So that correction is done in camera. So no changes in settings I take it? I'm seriously am considering buying one.so thanks a bunch for the information again.

[Tronhard]

Glad this helps! 
I emphasize that the issue was not 'fixed' per se,  it was intended and inherent from the start in the design of 24-240 and 14-35L lenses.  I expect that we will be seeing more of this combination of software and hardware for lenses working seamlessly together in future.  It makes optics that would otherwise be impossible, or very expensive and big able to be marketed for a much reduced price and yet still perform.  If you don't deliberately turn off the corrections they are applied to JPG automatically.
We are used to seeing that mixture of hardware and software in camera bodies for exposure, focusing, tracking etc., this is simply another application of the same principle.
I hate changing lenses in the field, and in the case of Mirrorless Interchangeable Lens Cameras (MILCs), for units such as yours that don't have a conventional mechanical shutter that normally protects the sensor, you don't want to expose the sensor to the world, as they attract dust that will obvious in your photos.  Cameras like the R5, R6 series and R7 have a mechanical shutter but the rest not in the same way.

If you ever have to take off a lens, turn the camera off (a live sensor has a mild charge and thus a dirt magnet), point the body lens downwards to avoid dust falling into the lens mount, and take off the lens.  Put the new one on, and then cap the now redundant lens.

[stromy93]

Thanks again for the help. Much appreciated.

[Tronhard · Accepted solution]

Happy to.  You can do us both a favour and mark my explanation as a solution - that stops everyone trying to fix your issue and sending you lots of notifications when you are sorted. Someone with a similar question can thus find this thread and not go through it all themselves.