How much extra reach for R7 vs R5 with the RF 100-500mm and extenders?

[AlanF]

Just how much extra resolution do you get using a telephoto on the 32 Mpx APS-C vs the 45 Mpx full frame R5? The answer is not 1.6x, the crop factor. The upper limit will be the ratio of the lengths of the pixels, in this case 4.39/3.2, = 1.37. But it will be lowered by various factors including diffraction from the narrow apertures of a lens, noise at higher isos, the strength of the low pass filters, and the effects of the Bayer filter. Also, how much extra reach will you get from the 1.4x and 2xTCs? Again, it's not 1.4 and 2x because of the effects of image degradation and decreased apertures. I've measured what I get in practice under the conditions I tend to use for my nature photography, with isos in the range 500-1500 and the RF 100-500mm at wide open apertures, from resolutions of lines on charts.

Extenders on the R5. The relative resolutions at 500mm/f7.1:700mm/f10:1000mm/f14 are: 1:1.14:1.4. And for the 500mm/f7.1:800mm/f11 = 1.4. There's only a 14% increase in resolution in using the 1.4x.

Extenders on the R7. The relative resolutions at 500mm/f7.1:700mm/f10:1000mm/f14 are: 1:1.33:1.4. And for the 500mm/f7.1:800mm/f11 = 1.4. Here, the 1.4x gives a 33% increase. I don't know why there is a difference from with the R5.

R7 vs R5. At 500/7.1, the R7 gives in practice only 14% more; with the 1.4xTC 33% more, and with the 2xTC the aperture is so narrow etc there is no real extra reach with the R7.

To get the best advantage on using TCs, you need a wide aperture lens, like an f/2.8 or f/4, to lower the increases in diffraction above the diffraction limited apertures. To get the best out of the R7, again wide lenses are essential. But optyczne.pl, which measures the sensor resolutions, gives the R7 only a 14-15% advantage of the R7 at f/4.

In practice, it means to me I don't use the 1.4x on the R5 but I will use the 2x.

 

[neuroanatomist]

Wide apertures, or bigger pixels. Or both.

 

[AlanF]

Wide apertures, or bigger pixels. Or both.

The 800/11 and 600/11 are optimised for DLA of 20 Mpx FF cameras.

 

[kaihp]

Alan, how would the shoot-out between the RF 1.4x and 2x TC on the RF100-500 look like on a "low MPix" camera like the R3?

Are the number you quote calculations or measurements?

I'm considering an extender for the RF100-500, and torn between them.

 

[AlanF]

Alan, how would the shoot-out between the RF 1.4x and 2x TC on the RF100-500 look like on a "low MPix" camera like the R3?

Are the number you quote calculations or measurements?

I'm considering an extender for the RF100-500, and torn between them.

The numbers are measurements. The 2x extender should, in theory, improve relative to the 1.4x as the Mpx get fewer. However, I would try them out on your camera before finally committing.

 

[EricN]

I remember many people commenting about the lens only working between 300 and 500. Was that difficult for you to adjust to?

 

[AlanF]

I remember many people commenting about the lens only working between 300 and 500. Was that difficult for you to adjust to?

It's a design flaw. But, in practice for me it doesn't make much difference as I use the extenders only when I need the full extra length and - I attach the extender only when required in the field. The extra length makes no difference either as I carry on a shoulder strap when the extender is on and wouldn't pack the camera and lens with extender attached anyway (I carry the extender in a small waist pouch along with spare batteries etc when in the field). I blow hot and cold about using extenders as their disadvantages do not always outweigh their extra reach. As you know, I do like to use the 2x on the RF 100-500 at mfd for insects to get about 0.5x magnification for almost macro photography.

 

[kaihp]

The numbers are measurements. The 2x extender should, in theory, improve relative to the 1.4x as the Mpx get fewer. However, I would try them out on your camera before finally committing.

Thanks. I would love to try both, but the dealer here only has a 2x TC loaner, but no 1.4x TC.

The EF 1.4x TC III worked really well on most/all telephone EF lenses, but it was only on the 300/2.8 II where I was reasonably happy with the IQ and focus speed of the 2x TC. This makes me hesitant of getting an RF 2x TC (once bitten twice shy).

 

[AlanF]

Thanks. I would love to try both, but the dealer here only has a 2x TC loaner, but no 1.4x TC.

The EF 1.4x TC III worked really well on most/all telephone EF lenses, but it was only on the 300/2.8 II where I was reasonably happy with the IQ and focus speed of the 2x TC. This makes me hesitant of getting an RF 2x TC (once bitten twice shy).

I blow hot and cold on the extenders. When the 2xTC focusses well, as it does for close distances when I do insects, it's great. For small distant objects the AF is hit and miss - when it hits it's good but it can miss a lot of the time. For the intermediate distances and the subjects are larger, it hits a lot but then the bare lens is often good enough. The 1.4x doesn't add that much. I agree about the 300/2.8II, and if you look at the Canon MTFs, that lens loses less IQ with the 2x than just about any other.

 

[kaihp]

For the intermediate distances and the subjects are larger, it hits a lot but then the bare lens is often good enough. The 1.4x doesn't add that much.

I just read up on Bryan Carnahan's review of the RF extenders and he is unusually skeptic about the RF 2x TC.

From the review summary:

While I readily recommend photographers add a Canon RF 1.4x extender to their kits, I'm more reserved about the 2x recommendation. The noticeable impact this extender has on image quality is the primary reason for that reservation. That said, when you can't get any closer and can't use a lens with a longer native focal length, using the 2x extender makes sense.

 

[neuroanatomist]

I just read up on Bryan Carnahan's review of the RF extenders and he is unusually skeptic about the RF 2x TC.

That aligns with my tests of extenders on the EF 600/4 II. I found the EF 2xIII to give sharper output than the RF 2x. The RF 2x was similar to the EF 1.4xIII and RF 1.4x stacked.

 

[AlanF]

That aligns with my tests of extenders on the EF 600/4 II. I found the EF 2xIII to give sharper output than the RF 2x. The RF 2x was similar to the EF 1.4xIII and RF 1.4x stacked.

I wonder what your tests would be like on the EF 600/4 III and the RF 600/4. They are optically identical. On Bryan's charts, the RF 600 on the R5 looks marginally sharper than the EF600 III on the 5DSR.
https://www.the-digital-picture.com...meraComp=979&SampleComp=0&FLIComp=0&APIComp=0

Add the EF 2xTCIII to the EF600 and the RF 2x to the RF 600, the RF pair at 1200mm look sharper than the EF pair, though both aren't up to par.
https://www.the-digital-picture.com...meraComp=979&SampleComp=0&FLIComp=2&APIComp=0

It's similar with the RF 400/2.8 and EF 400/2.8III. What's the RF 2x like on your 100-300/2.8? Looks good on Bryan's charts, but not as sharp as the RF 100-500 at 500.

 

[kaihp]

That aligns with my tests of extenders on the EF 600/4 II. I found the EF 2xIII to give sharper output than the RF 2x. The RF 2x was similar to the EF 1.4xIII and RF 1.4x stacked.

That's pretty discouraging information.
Of course your particular copy of the RF 2x TC could be a lemon, but if Bryan and others see the same, we've got a (bad) trend going.

Someone just posted adverts for selling both the RF extenders 2nd hand close to me. Gonna go have a look at them and see how they look on the 100-500mm.

 

[Czardoom]

Totally unscientific observations, but I have owned both RF 1.4x and 2.0x extenders to use with my RF 100-500, and found them to be no better - or perhaps better stated, not enough better - than just cropping. So sold them both. My observations, with extenders in general, shooting hand held mostly, is that they are really only worth it if the lens is fast, f4 and lower, and has "pro quality" sharpness. Again I should stress, no test charts, no in-depth comparisons were done. Just enough shots taken with and without extenders to be able to compare and decide whether or not to buy/keep the extenders. The RF 100-500 is certainly pro quality sharp, but add the extenders and you are getting into pretty slow lens territory, especially with the 2x.

My feeling is - and I have read others who have also said this - is that contrary to what most folks would want to use the extenders for, extenders are most useful at short and medium distances. Once you get into long range shots, atmosphere, difficulty in holding the camera steady, diffraction from higher aperture settings (with the 2x usually) or higher ISO if shooting birds or wildlife, all reduce the effectiveness of the extenders.

 

[AlanF]

Totally unscientific observations, but I have owned both RF 1.4x and 2.0x extenders to use with my RF 100-500, and found them to be no better - or perhaps better stated, not enough better - than just cropping. So sold them both. My observations, with extenders in general, shooting hand held mostly, is that they are really only worth it if the lens is fast, f4 and lower, and has "pro quality" sharpness. Again I should stress, no test charts, no in-depth comparisons were done. Just enough shots taken with and without extenders to be able to compare and decide whether or not to buy/keep the extenders. The RF 100-500 is certainly pro quality sharp, but add the extenders and you are getting into pretty slow lens territory, especially with the 2x.

My feeling is - and I have read others who have also said this - is that contrary to what most folks would want to use the extenders for, extenders are most useful at short and medium distances. Once you get into long range shots, atmosphere, difficulty in holding the camera steady, diffraction from higher aperture settings (with the 2x usually) or higher ISO if shooting birds or wildlife, all reduce the effectiveness of the extenders.

The effectiveness of extenders depends also crucially on the resolution of the sensor. For low resolution sensors where the diffraction blurring is small relative to the size of the pixels, doubling the focal length should in theory double the resolution. At the other extreme, where the sensors are of very high resolution and diffraction is limiting, resolution is independent of increasing the length using an extender - resolution depends then on the diameter of the front lens element (entrance pupil) and is independent of the focal length and f-number of the lens. With the R7 and an f/11 lens, extenders are going to be pretty useless in theory. At f/7.1 I with the 100-500mm I can see some enhancement under the right conditions with a 1.4x but the 2x is a waste of time.

 

[Czardoom]

The effectiveness of extenders depends also crucially on the resolution of the sensor. For low resolution sensors where the diffraction blurring is small relative to the size of the pixels, doubling the focal length should in theory double the resolution. At the other extreme, where the sensors are of very high resolution and diffraction is limiting, resolution is independent of increasing the length using an extender - resolution depends then on the diameter of the front lens element (entrance pupil) and is independent of the focal length and f-number of the lens. With the R7 and an f/11 lens, extenders are going to be pretty useless in theory. At f/7.1 I with the 100-500mm I can see some enhancement under the right conditions with a 1.4x but the 2x is a waste of time.

Good point. Always good to get your input Alan!

 

[kaihp]

My feeling is - and I have read others who have also said this - is that contrary to what most folks would want to use the extenders for, extenders are most useful at short and medium distances. Once you get into long range shots, atmosphere, difficulty in holding the camera steady, diffraction from higher aperture settings (with the 2x usually) or higher ISO if shooting birds or wildlife, all reduce the effectiveness of the extenders.

Thanks for your considerated points Czardoom. What would you define as "medium" distances with 500mm native lens (RF100-500, obviously)?

Log-scale distance is probably a good measure - above 10m? 20m? 50m? 100m? 200m? (this depends clearly on the pixels-per-duck measure [ie: apparent size of the target on the sensor] as well).

With the deer and Owl I'm shooting at the local part area, I'm probably in the 20-50m range. Same if I shoot motorcycle trackdays locally, but if I go to the TT Assen (as a spectator), I'm quickly out in the 50-100-200m bracket, and my gut feeling is that this would be outside the "medium" distances (so "far distance").

 

[AlanF]

Thanks for your considerated points Czardoom. What would you define as "medium" distances with 500mm native lens (RF100-500, obviously)?

Log-scale distance is probably a good measure - above 10m? 20m? 50m? 100m? 200m? (this depends clearly on the pixels-per-duck measure [ie: apparent size of the target on the sensor] as well).

With the deer and Owl I'm shooting at the local part area, I'm probably in the 20-50m range. Same if I shoot motorcycle trackdays locally, but if I go to the TT Assen (as a spectator), I'm quickly out in the 50-100-200m bracket, and my gut feeling is that this would be outside the "medium" distances (so "far distance").

The key factor is the level of detail on the subject and is the subject close enough to resolve it. If the detail is fine and just below resolvable on the bare lens, then an extra 40% of effective focal length may well resolve it. If the detail is resolvable by the bare lens then all the extender can do is to put more pixels on it, which you can do by upscaling. The same applies if the subject is so far away that extra detail can’t be resolved by adding a TC. So, I don’t think you can put numbers on the distance.

 

[scyrene]

The 800/11 and 600/11 are optimised for DLA of 20 Mpx FF cameras.

So I'm not imagining the extra resolution I get on the R6 with these combinations? I tested on the moon when I got the 2x extender and could see a little more detail at 1600mm compared to 1120.