Canon Extender EF 1.4x III Review -

keribillen wrote:

Hi Marco,

I just bought a 100-400 lens with a 1.4x extender, and am looking forward to some astronomical shots with this combo. I just about captured the rings of Saturn with my Canon 70-300L last year, so hoping to better that this year. I googled 'moon 400mm teleconverter aps-c', and your post here was one of the top results. I love these shots of yours, especially the detail on Jupiter and its moons. Great stuff!

All the best, Keri

Hello Keri. I'm sorry it took a few days but I only just saw your post. You should be well served by that lens combination. Though if you have the Mk 1 verision of this lens and the Mk 1 version of the 1.4x extender, the results may be softer than what I am getting with the Mk2 lens and the Mk III Extender combo. Canon made some refinements to the Mk2 lens and the Mk III Extenders that enables them to produce slightly sharper results. Even with the Extenders on this lens, the planets like Saturn and Jupiter are still fairly small in the frame.
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EOS M6 + EF 100-400mmL II lens @ 400mm + CPL filter (slightly cropped).
Be sure not to use the OVF for this. The sun still emits powerful light and UV light as well. It's also risky to subject your sensor to that type of light. But when the sun it setting and is dim on the horizon, I'll only take a shot like this with the LCD Live View.

EOS M6 + EF 100-400mmL II lens @ 400mm + CPL filter.
Be sure not to use the OVF for this.  The sun was dim because of the bushfire smoke here.

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EOS M6 + EF 100-400mmL II (uncropped) @ 100mm (shot before the image below)

EOS M6 + EF 100-400mmL II (cropped) @ 400mm (shot after the image above)

EOS 6D + EF 100-40mmL II lens + EF 2x III Extender (image has been slightly cropped)
The moon is orange from the Australian Bushfires and the smoke they produced.

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I photographed Saturn last year using the EF 100-400mmL II lens and the two Mk II Extenders during occultation in August 2019. Note that using an APS-C sensor gives us a 1.61x magnification (equiv) compared to Full Frame which gives is more light to play with but no additional crop. I added the EF 1.4x III Extender and the EF 2x III Extenders. An EF12 Extender Tube was used to enable me to mount both Extenders back to back. It acted as a spacer. I then used the edge of the moon that was slipping into shadow (which showed craters)
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Live View on the EOS M6 LCD display (no magnification) - waiting for occultation

Saturn in the Blue Sky around sunset - approaching the moon before occultation

Closeup (CROPPED Significantly) of Saturn passing behind the moon.

Saturn disappearing behind the moon

Uncropped - Saturn reappearing from behind the moon.

Saturn on the LCD - 10x magnification

A view from the camera with a Video Still (two blended images - one for lunar detail) - In this shot, Saturn has reappeared from behind the moon during occultation.

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I note that without using any extenders, the aperture on this lens remains a constant f/4.5-5.6 and that means it would likely perform like the large refactor telescopes with 400mm focal lengths. Those scopes are usually well made with field-flatteners etc but with a tripod mount that has EQ tracking on it, you ought to be able to capture some amazing shots of other deep sky imaging subjects. 
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Despite me using the 2x III Extender in some of the shots above, the 1.4x III still gives me slightly crisper results with a lot more light to play with, regardless of the camera.  This means a lower ISO can be used and you can blow up your image slightly if you want, without noticeable IQ degradation. I almost bought a dedicated telescope recently for planetary photography but I'm now aiming at one of those Astrograph Primes designed for digital photography rather than direct observation.  I might start with an EQ mount tripod of reasonable quality to try out with the EF 100-400mmL II lens to see what I can get at 400mm with tracking.