60-600mm lens + 3 extenders = Total focal length?

[Okimar]

I'm a novice and completely confused after researching this question

Can anyone please tell me what the combined mm and magnification this with this arrangement on my Canon R?

 

 

[Tronhard]

Hi and welcome to the forum:

Hmmm...   I have the Sigma 60-600mm myself and your arrangement is not a construct I would recommend.  I assume you are keen to increase the size of an image within your photos.  But, to answer your question, there are several aspects to consider here.  The effective focal range of the lens, the impact on the aperture range, and its ability to gain focus and get an exposure reading.  Not to mention structural integrity and weather sealing.

Native focal range of Sigma is 60-600mm f/ 4.5-6.3.  Its performance in this configuration is excellent and can use all focusing and exposure modes of the camera to which it is connected.  It has good image stabilization.

Attaching an extender will have several impacts on the lens performance.
Adding a 1.4 extender will increase the effective focal length by a factor of 1.4 but also reduces the effective aperture performance by at least a stop.  That results in a focal range of 84-840, f/6-8 at best.
Adding a further 2x extender doubles the focal length again but loses you a further two stops of aperture
so, 168-1680 f/9-f11 (at best).  It is likely this will adversely effect focus and image stabilization.
But it's not as simple as that.  Depending on the version of each extender (and the one closest to the body appears to be old) camera and lens to which it is attached, will cause the number of effective focal points to be reduced to basically ONE and focus will be pedestrian at best.  Given this is not a native Canon lens, Canon does not support or predict how the lens will behave, and I doubt Sigma would be too keen to make any comments with the extenders and the EF-RF adapter added in the mix.
Finally, you are compromising the structural integrity and certainly any weather sealing with so many mechanical joints, each of which adds a risk factor.

So, the bottom line is this.  If you really want to get up and close with a subject, I would strongly advise to use the lens in its native format.  The quality of the image will be better, it will focus quickly and accurately and perform as advertised.  I use this lens frequently and it is a great unit with both DSLR and R-series MILCs.
The more stuff you attach, the more the performance and image quality will suffer, and the more the lens will be hard to hold steady, and to focus.  The light performance of all that stuff will likely be that close to a blind person in all but the brightest light.

With all this in mind, exactly what subjects do you want to shoot and what do you want to produce?  The EOS R has a 30MP sensor, so if you are producing images for social media, digital display or even moderate size prints, you can crop the image to contract the Field of Capture.

The following examples were taken by the Sigma 60-600, sans extenders, and shot on the Canon EOS 6D, a 20MP sensor.
NZ Kaka EOS R6, Sigma 60-600@ 475mm, f/6.3, 1/400sec, ISO-1600
R6, Sigma 60-600@600mm, f/6.3, 1/400sec, ISO-1600

My advice is use the lens as designed and massively increase your chances of a decent shot.

[Okimar]

Thank you for your detailed reasoning. 

Fortunately, I live in Central Florida and it's constantly bright a heck here and can get pretty good shots for fun with it for fun.

Photography is something I'm getting into to just have something to do since I'm restricted to a wheelchair. 

[wq9nsc]

If you start with an extremely high quality lens and put a 2X extender on it, you end up with a mediocre lens and the Sigma 60-600 is decent but it isn't like a Canon L series great white prime.  Putting three extenders plus an extension tube on the best glass Canon makes would result in image quality not befitting any quality camera.  And as Trevor notes, you are losing at least 5 f stops of light in the process along with any ability to properly autofocus.

If your goal is capturing quality images, forget the idea of multiple additions to the lens to increase the focal length/magnification of the lens.  Extension tubes can be useful for macro photography with some lenses and a single extender (preferably of the 1.4X variety) will work OK with a number of decent lenses.

Trying to combine a number of extenders on a lens isn't compatible with the reason people buy quality cameras and glass in the first place, to capture quality images. 

Rodger

[Okimar]

The main reason I'm playing around with this configuration is to see what I can see in the night sky, but I don't have a tracker, so it's just me and my wife trying to look at the full moon.

[johnrmoyer]

I have stacked extenders for fun. I hope you have fun too. The biggest obstacle to photographing the moon is changes in air density between the camera and the moon.

The extender will

1. increase the F number
2. leave the minimum focus distance unchanged
3. reduce the contrast for small features
4. possibly magnify any defects in the lens
5. possibly increase small aperture diffraction blur

Canon DPP software "digital lens optimizer" does well at removing small aperture diffraction blur. If your camera can save DPRAW, then the DPRAW tool in DPP can correct some of the loss of contrast for small features. With extenders, I have been able to see the moons of Jupiter. The moon picture below was hand held and with a shutter speed of 1/20 second gave the IBIS a workout even though I was sitting in a chair with my elbows braced.

Others make better moon photos, but this was fun for me.

A Bumble Bee (Bombus pensylvanicus) was on a Zinnia in Norman, Oklahoma, United States on September 2, 2021. I made this photo with a very old lens as an experiment. I purchased the lens in 2011 and nearly wore it out. For this photo, it was attached to a newer camera body with an adapter with two telephoto extenders.

Canon EF70-300mm f/4-5.6 IS II USM ; Kenko Teleplus HD C-AF 2X DGX teleconverter ; EOS 80D ; This was taken hand held while sitting on a chair on my front porch. The gimp gmic plugin Richardson-Lucy deconvolution was used to remove small aperture diffraction blur. F/11 is wide open for this combination of lens and teleconverter. Focus was manual. After cropping and resizing to 40%, an unsharp mask was applied. https://www.rsok.com/~jrm/2017Feb07_birds_and_cats/2017feb01_cardinal_IMG_0929.html

Moon seen from Norman, Oklahoma, September 14, 2022 ; F/16 ; Focal length 1120mm ; EF100-400mm f/4.5-5.6L IS II USM +1.4x III + Kenko TELEPLUS HD C-AF 2X DGX

[kvbarkley]

On the other hand, if you are just doing it for fun, go for it. But expect Holga quality everywhere but *maybe* the very center. The good thing about the R's is that you can still focus at very small apertures. Ken Rockwell did something like this.

[Okimar]

I'll have to search for his name to see what he was doing. Thank you.

[Okimar]

I appreciate the replies, but I still haven't gotten an answer to if anyone knows how to calculate the combined mm and x of magnification this combination equals, which everyone but me seems to know and mentions in their YouTube videos.

[kvbarkley]

Trevor gave you the focal length.

The extension tube complicates things. It is straight forward without it.

Magnification depends on focal length *and* close focus distance. The extension tube will decrease the minimum focal distance at the expense of focusing at infinity, but it is unclear how much.

Your best bet is to measure it, and back calculate.