Hello everyone. I own the rf 100-400 lens. I like it. So light and small yet iq is good. Fot the extra reach should I buy the 1.4 extender and use it with the 100-400 or get the 600 f11 ? Has anyone comperad the af speed and iq of the two set ups? I have an R7 btw.
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Rf 100-400 plus 1.4 Tc or Rf 600 F11
- Thread starter OlcayK
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Johnnyxbow
Forum Enthusiast
Johnnyxbow
Forum Enthusiast
Sorry just got a bit further down the thread and this has been answered
Obviously, at some f/number you will see diffraction blurring. The RF100-400 goes up to f/45, and I think we can all agree that at f/45 diffraction blurring will be significant on the R7, even without pixel peeping.
So it also depends on your definition of pixel peeping. If you only print full frame at 4x6" then you probably won't see diffraction blurring at any aperture the camera would choose in auto exposure on the R7. But you also wasted your money, because an R10 would be just as good.
Assuming you want to put the 32.5Mp investment to good use, then you will want the diffraction blur to be contained to just a few pixels, rather than several pixels, regardless of the exact definition. At f/11 the Airy disc diameter is about 5 times the pixel pitch, so it is covering about 20 pixels. It doesn't take much pixel peeping to see that.
Steve Fink
Senior Member
I misspoke on the the Ef 1.4x. It's a Tamron 1.4x. It works with the EF to RF convertor using my EF 300 F2.8 but not with the 100-400mm.
I had the RF 1.4x and tried it with my 100-400mm. I sent it back not thinking the results were that good. I also thought it was overpriced.
I suppose that I should apologize for going somewhat off-topic in a discussion of diffraction.
At some level, I agree. When someone posts f/5.2 as a diffraction limited f/number for an R7, it worries me a little. It might cause someone to avoid lens choices that could still give good images.
(I don't own an R7.)
Maybe many people rent lenses and do serious testing before making a purchase, but I'm not one of those people.
I posted that f/5.2 is a diffraction limiting aperture, and later clarified that this is where diffraction blur begins to be a factor, not a limit per se. I do own an R7 and the RF100-400 is practically glued to it, and I mostly shoot at 400mm f/8. I can see that diffraction blur is noticeable in cropped images, but I accept that up until I can use my RF800/11. I don't add the 1.4x TC @400mm with the R7 because I know it won't help as much as it does with the R5 (which isn't much).
You find an 800 f/11 worthwhile on an R7, or not?
Back to the OQ, yes, someone has compared the IQ of the two set ups, but on an R5:
Canon RF 100-400mm F5.6-8 IS USM Lens Image Quality (the-digital-picture.com)
The RF600/11 has a superior IQ to the RF100-400 @ 560mm f/11. It's not surprising that a prime lens would beat a zoom with a TC at the same f/number. So when you need 600mm or more, you will be better off with the prime. But it's useless below 600mm.
I would not buy the RF1.4x to use with the RF100-400 on the R7 (I have all three). There is not much excess resolution with that combo that a 1.4x can reveal. If you had one, you could use it if you like, but I don't bother with mine (I specifically got the R7 so I wouldn't need to use the 1.4x with the RF100-400 as with the R5). If you had or planned to get another lens that can use it, that might make a difference, but I would get the other lens first.
I would just crop the RF100-400 until you can get the RF600mm. Then if you wanted to spend some more, instead of the 1.4x, I would get an R10 to put on the RF600. You could also get a low-cost FF body to bridge the gap between 400-600mm on an APSC body if you prefer. But this combo would let you have the best of both without having to switch lenses. That can be really handy if your subject moves towards you.
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Diffraction is even more visible @ f/11 compared to f/8, but if I need that much focal length, then yes, I find it worthwhile on the R7. I didn't think the 600/11 was worthwhile because it has the same entrance aperture as the RF100-400mm. But the 800/11 has twice the entrance area, so that makes a big difference.
Thanks for the link, although, for me, it comes up as a comparison of the 100-400/1/4X at 560mm to the 800 mm f/11. (Simple enough to switch it to the 600 f/11.)
The 100-400 plus 1.4X shows more lateral color than either of the primes. I wonder how much that could be improved in post processing? (I don't expect miracles.)
OK, I tested the RF100-400 +/- RF1.4x. on the R7. TLDR: no improvement in resolution with the TC.
I used MTFmapper with a 1200 dpi A3 lensgrid chart at 15m. With the 1.4x, peak MTF50 resolution topped out at 39 lp/mm at 540mm f/14 (stopped down 2/3 stop). Without the TC at the same distance and cropping, it was 55 lp/mm at 400mm f/10 (also stopped down 2/3 stop). The peak resolution at 2/3 stop down is consistent with my past testing on the R5, so no surprise.
As a confirming test, I also tried the RF100-500mm L-series at 400mm on the R7. It topped out at over 70 lp/mm at the same distance. I would not read too much into that comparison, other than that the L-series lens blows away the plastic lens. I did this test to make sure the test chart has excess resolution, so 55 lp/mm is the limit of the lens, not the test chart or camera sensor. MTFmapper measures the total system resolution, which includes everything, so we need to make sure the limiting factor is the device under test.
This means that the TC made no improvement because we would expect the TC to do better than 55/1.4x=39 lp/mm. So the 1.4x TC on the RF100-400 makes the diffraction blur 1.4x * 1.4x larger (i.e. the Airy disc covers twice as many pixels) without adding any monochrome resolution. There could be some improvement in color resolution, but I didn't test that.
Bottom line: don't waste money buying an RF 1.4x TC to put between the RF100-400 and the R7. There is no excess resolution that the TC can reveal on the R7 sensor's ~3-micron pixels.
I used MTFmapper with a 1200 dpi A3 lensgrid chart at 15m. With the 1.4x, peak MTF50 resolution topped out at 39 lp/mm at 540mm f/14 (stopped down 2/3 stop). Without the TC at the same distance and cropping, it was 55 lp/mm at 400mm f/10 (also stopped down 2/3 stop). The peak resolution at 2/3 stop down is consistent with my past testing on the R5, so no surprise.
As a confirming test, I also tried the RF100-500mm L-series at 400mm on the R7. It topped out at over 70 lp/mm at the same distance. I would not read too much into that comparison, other than that the L-series lens blows away the plastic lens. I did this test to make sure the test chart has excess resolution, so 55 lp/mm is the limit of the lens, not the test chart or camera sensor. MTFmapper measures the total system resolution, which includes everything, so we need to make sure the limiting factor is the device under test.
This means that the TC made no improvement because we would expect the TC to do better than 55/1.4x=39 lp/mm. So the 1.4x TC on the RF100-400 makes the diffraction blur 1.4x * 1.4x larger (i.e. the Airy disc covers twice as many pixels) without adding any monochrome resolution. There could be some improvement in color resolution, but I didn't test that.
Bottom line: don't waste money buying an RF 1.4x TC to put between the RF100-400 and the R7. There is no excess resolution that the TC can reveal on the R7 sensor's ~3-micron pixels.
Steve Fink
Senior Member
Without doing an official test, I came to the same conclusion and returned my RF 1.4x. I thought it was overpriced for the results I was getting. I like the RF600 F11 better than the RF 100-400mm plus the 1.4x, at least IMO.
Unrelated, I do question the IQ of my EF 300mm F2.8(v1) with an EF2x (v1?) added. IMO, the combo works better on the 5D MKIV than the R7. I don't have the means/skills, or time, to officially test it however.
Steve Fink
Senior Member
I agree with this. Both the RF600F11 prime and the RF 100-400mm zoom work well individually. I suggest buying both, since the price for each isn't so bad.
Thanks for the analysis, very interesting. Based on this results, would it be a stretch to infer that the resolution obtained with the RF 100-400 at 400mm F8 would be similar in detail to the RF600 F11 on the R7 due to diffraction, and therefore that investing in the 600mm is also not really worth it if you have the RF 100-400?
Forgive me if I missed something, but maybe one of the big benefits of the TC is that you are able to AF better on small birds at a distance?
I have had some moments where the R7 with the RF 100-400mm was not able to detect the bird because it was too small in the frame. I was considering the TC for these instances.
Jeroen
Alastair Norcross
Forum Pro
Yes, one of the many considerations that actual shooting experience reveals over obsessive chart-based testing.
Both lenses have about the same entrance aperture: 400/8=50mm vs. 600/11=55mm, so I decided not to get the RF600/11 because I didn't expect a big difference in monochrome resolution, which is most important in my work. The 600mm probably does have an advantage in contrast because it is a prime lens with 10 elements in 7 groups vs. 12 elements in 9 groups for the zoom, but it uses diffractive optics, so that may also make a difference.
I don't know the answer. I suspect there is little improvement in monochrome resolution because the entrance aperture is limiting. But there could be a significant difference in color resolution because the diffraction blur is spread over fewer pixels of each RGB color; so the extra pixels from the 600mm could be useful, especially since the prime has less CA, even before putting a TC on the zoom. Those extra pixels are not as useful with the TC on the zoom because the TC reduces contrast and increases CA.
I doubt the TC will help with AF on the RF100-400 because it does not reveal any extra detail for the AF to use; in fact, it makes the subject darker and less sharply focused, which should make AF worse in general.
There could be a difference with eye detection where the camera will detect a larger, but blurrier, eye, so it will AF at a more optimal distance. But if the bird is too small for eye detection to work, I doubt you will be happy with the final image (unless it's one bird in a large group, but then eye detection isn't needed).
The only good reason to use a TC is to better match your lens' resolution to your sensor's resolution. With an L-series lens on a FF body, there is excess lens resolution for the TC to bring out. But with the RF100-400 on the R7, nothing is left on the table.
Steve Fink
Senior Member
Clearly the RF 600mm F11 gives more reach the the RF 100-400mm with 1.4x TC effective 560mm F11. IMO, IQ is much better with the 600mm as well as well as AF as well. Add to the fact that the 1.4x TC is not that much cheaper than the 600mm F11, it's a no brainer for me. I use both the 600mm and 100-400mm depending on the distance the subject(s) are away. If too far away, I simply don't shoot. Cropping too much rarely seems to give great results for me.
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