Canon RF24-50 f/4.5-6.3 IS STM w/ Nauticam WACP-1 & WACP-C

Hi,

I have the new Canon RF 24-50 lens and have been testing it with the N120 version WACP-1 and WACP-C on my Canon R5C/Nauticam R5C housing. 

The good news is that the lens works perfectly with the WACP-1 (N120) version without any extension rings. In fact, with this setup, it does not vignette at 24mm and can be extended all the way to 50mm without touching the glass. So you get the full zoom range and presumably a 140-150 degree field of view at the wide end with 24mm.  Autofocus is great on land (haven't tested in the water yet). Image quality looks good too, but I'll try to do some detailed comparisons against the old EF 28-70 F3.5-4.5 which is the recommended solution for the WACP-1/WACP-C from Nauticam's port charts currently.

The situation with the WACP-C is a bit less ideal. This is because the WACP-C is N100 by default and needs a N120 to N100 port adaptor to use with the Nauticam RF line of houses. I have the 25mm adapter, which I believe is the shortest one they make at the moment. But with this adapter, the RF 24-50 sits too far back from the back element of the WACP-C. There's significant vignetting both at 24mm and at 28mm focal lengths. It doesn't really clear up until close to 35mm, which limits the usefulness of this combination. I think a ~10mm N120-N100 adaptor would be needed (or a native N120 version of the WACP-1) in order to take full advantage of this lens with the WACP-C. Too bad..

34 minutes ago, dreifish said:

Hi,

I have the new Canon RF 24-50 lens and have been testing it with the N120 version WACP-1 and WACP-C on my Canon R5C/Nauticam R5C housing. 

The good news is that the lens works perfectly with the WACP-1 (N120) version without any extension rings. In fact, with this setup, it does not vignette at 24mm and can be extended all the way to 50mm without touching the glass. So you get the full zoom range and presumably a 140-150 degree field of view at the wide end with 24mm.  Autofocus is great on land (haven't tested in the water yet). Image quality looks good too, but I'll try to do some detailed comparisons against the old EF 28-70 F3.5-4.5 which is the recommended solution for the WACP-1/WACP-C from Nauticam's port charts currently.

The situation with the WACP-C is a bit less ideal. This is because the WACP-C is N100 by default and needs a N120 to N100 port adaptor to use with the Nauticam RF line of houses. I have the 25mm adapter, which I believe is the shortest one they make at the moment. But with this adapter, the RF 24-50 sits too far back from the back element of the WACP-C. There's significant vignetting both at 24mm and at 28mm focal lengths. It doesn't really clear up until close to 35mm, which limits the usefulness of this combination. I think a ~10mm N120-N100 adaptor would be needed (or a native N120 version of the WACP-1) in order to take full advantage of this lens with the WACP-C. Too bad..

Sounds like a great option, though probably needs an in-water test to confirm it all works as it should.  It should be relatively easy to machine an adapter that would work with the WACP-C if you did it without adding locking devices.

A few shots for comparison. First, the RF 24-50 at 24mm, 28mm, 35mm and 50mm. All shot at F5.6 except the last at F6.3

Then the EF 28-70 F3.5-4.5 at 28, 35 and 50mm. All shot F5.6 except the 50mm at F6.3 to compare apples to apples.

I've left profile lens correction off, so you can immediately see just how much barrel distortion the new RF 24-50 shows without correction. HUGE difference. One you apply the lens profile correction in Lightroom though, things normalize. I'd say the image quality (sharpness and contrast) is pretty comperable. Maybe a touch better on the old EF 28-70 though, especially in the corners. The 24-50 does have image stabilization though and a quieter, faster auto-focus motor. And the advantage of going to 24mm of course..

You can get a custom made adapter ring down to 10mm for the wacp-c
However considering your port system is N120 and the wacp-1 works I would abandon the WACP-c entirely
There is 25mm of space in the mount and even with a 10mm ring you are far away from the 23.5mm of the wacp-1 so likely you will have some residual vignette perhaps it will work at 28mm just fine
Performance tests for this type lens on land are not a good indication of how it will work in water other than the vignette I would wait until you have taken this into a pool with a test set up


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I measured the distance from the port opening to the back of the glass on the WACP-1 and WACP-C. Both are about 45mm, so you should need a similar extension with both systems if using the same lens.

This is supported by the Nauticam Port Chart, which, for the Canon EF 28-70 f3.5-f4.5 lens recommends a 25mm extension with the WACP-1 and a 25mm N120 to N100 adapter with the WACP-C. 

Of course, the size and weight difference between the WACP-1 and WACP-C is substantial, so I'd much prefer to keep the WACP-C for travel if I can find a 0-10 mm port adapter.

Nope

The back of the glass doesn’t matter because the lens in the wacp-c bumps on the rim which is 66mm unless it is very small. The other lens has a much wide opening

The wacp-c is 25.2 mm recessed because 11.5 mm are taken by the part that goes in the port and the glass is further down the metal rim. This is the official figure from Nauticam as well.

The wacp-1 has the same base lens however it simply has a 35mm adapter from which you take out 11.5mm at the lens total 23.5mm

The problem you have is that the wacp-c has a built in float collar so if you want to adapt to N120 mount you need an adapter ring the smallest is 15mm

You are now at 40mm and the rear lens opening is 66mm

The wacp-1 instead will sit at 23.5mm from the rim natively and is larger

There will be a delta of 16.5mm between the two this is not small you may try to get the 15mm adapter ring but it may still vignette

Considering your housing is N120 I would not consider the WACP-C

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@dreifish Have you got the chance to test it underwater and do comparison between the ef 28-70mm and rf 24-50mm with the wacp1? 

Im waiting for the zoom rings from nauticam, but won't get to test them until next month end. Would love to see the comparison between the two. 

I didn't end up testing it underwater except briefly in the pool. Based on the pool tests, I didn't see the image quality as an improvement over the 28-70.

I’d be interested to see a test with the WWL-C and these new 24-50 lenses (Nikon Z as well). Would be great to have a travel friendly option even if the IQ drops a smidge.