Hello,

as a user of a Canon R5 and a newcomer here in the forum (though I've been with wetpixel for many years), I'm currently switching from Seacam to Nauticam and my main question is about wide-angle - what else 😁.

For many years I photographed with the Canon EF 8-15/4 (often in combination with a Kenko 1.4x TC) behind a superdome or the small fisheye macro port (CFWA).

Now I would like to photograph with even better corner performance and more compact dimensions in the future, and therefore I was considering the Nauticam WACP-C.

Unfortunately, I can't find any informative reviews and/or images online about the best(!) camera/lens combination for Canon FF mirrorless cameras.

The RF 24-50 is recommended, but I'd like to know if, for example, the Canon RF 15-30 STM might offer better image quality (it only has 85° at the long end), or if an older adapted EF lens (e.g., the 28-80) would be advisable (it has 54° at the long end compared to the RF 24-50's 81°, so it would be much more versatile).

Or would I ultimately achieve comparable image quality with my old 8-15/4 lens in combination with the Kenko 1.4x TC? I'd probably have to stop down significantly more to avoid corner softness, even behind a super dome.

I also read here in the forum about the combination of the EF 8-15/4 with a 2x TC on a Sony, but I don't know if that works with Canon.

I know that the WACP-1 has up to 1 stop better image quality than the WACP-C (probably only visible in the corners), but the WACP-1 is simply too heavy - and a little bit too expensive for me as well.

Currently, I only own a Nauticam 8.5" Acrylic Dome Port (SKU # 18802) that came with the 2nd hand housing, which I could use with my Canon 8-15/4. However, I don't know if the image quality would be acceptable.

And btw: is there a WA lens recommended to the 8.5" Acrylic Dome?

Or does anyone have completely different considerations regarding excellent WA IQ?

Btw: I own a RF 14-35/4 and still have the EF 8-15/4, of course.

I'll definitely buy a Super Dome later at least for split or wreck shots... well, and I read here in the forum that a 140mm Nauticam dome is hardly recommended for the 8-15/4.

I would be grateful for any helpful answers!

Best regards,

Wahrmut

There have been various posts talking about the pros and cons of the various combinations of lenses and Nauticam wet optics as well as comparing performance of rectilinear lenses behind various domes. Few points you might consider:

The recommended dome for the Canon 8-15 in Nauticam is the 140mm dome. Fisheyes are much less sensitive to dome size compared to rectilinear lenses and smaller dome sizes help with getting closer to take CFWA shots. You can even use the 100mm Zen dome with the 8-15, though corner quality might take a small hit.

There is an extensive set of tests of various Canon optics in this post:

It tests the Canon 24-50 behind the WWL and doesn't have good things to say about it. The Nikon 24-50/WWL-C combination is generally rated quite well, however the Canon 24-50 kit lens seems to be significantly poorer in optical quality. Now this is with the WWL-C, however I recall other posts stating there is not much to pick between the WWL and WACP-C with other lenses. Bear in mind too that the 24-50 needs to zoom into 28mm to remove vignetting with the WWL-1 - the WWL-C is designed for 24mm lenses.

Rectilinear lenses generally require big domes, though some of the newer lenses that focus much closer work well with the 180mm dome. They lack the barrel distortion which enlarges the subject in the centre making fisheye images pop.

On the subject of teleconverters with the Canon 8-15 you mention the Sony 1.4x/2x with the Canon 8-15, these work because they place the Metabones adapter between the teleconverter and the 8-15. Optical quality is better than using the Kenko 1.4x. It needs this order of assembly as the nose of the 1.4x fits inside the the empty spacer of the Metabones adapter.

In this case the metabones acts like a 22mm spacer. In theory you could use the a RF 1.4x- Canon RF-EF -Canon 8-15, but the RF-EF won't work with an RF 1.4x. In theory again a Canon RF-EF-Canon EF 1.4x- aftermarket EF 12mm or 20mm extension tube- Canon 8-15 might work, but you'd need to test it.

In general I would say the Canon 8-15 is an exceptionally sharp lens and very hard to beat behind a dome as fisheyes naturally work well behind domes and is a great solution if you don't need extra reach.

The last point is that comparing diagonal field of view is a little misleading - you normally don't place subjects on the diagonal and fisheye lenses have the most stretching of the field in the corners. The WACP/WWL is like a zoomed in fisheye lens in terms of barrel distortion present. The horizontal field of a 180° (nominal) diagonal fisheye is about 144° while a WWL with 130° diagonal field has about a 106° horizontal field. The 8-15 is reported to achieve 175° diagonal field. This table compares horizontal and diagonal fields:

			Horizontal	Diagonal	Rect Equiv
15mm fisheye			141	175	4.5
15mm x 1.4			97	118	16
WACP at 28mm			106	130	13.5
WACP at 80mm			44.7	54	42

The Rectilinear equivalent is the focal length of a rectilinear lens with the same horizontal field.

You can compare the field you would get from a Canon 8-15 with 14mm FF equivalent rectilinear here, it's on m43 sensor so the comparison is the 8-15 at 8mm and the 7-14 at 7mm. This is equivalent to the 8-15 at 15mm and 14mm rectilinear on full frame.

6 hours ago, Chris Ross said:

It tests the Canon 24-50 behind the WWL and doesn't have good things to say about it. The Nikon 24-50/WWL-C combination is generally rated quite well, however the Canon 24-50 kit lens seems to be significantly poorer in optical quality.

True, I second this!

The very bad MFD of the 24-50 lens makes it also a pain in the .. underwater. When you are used to be able to focus right up onto the dome this becomes a real downer, as you cannot get really close without plugging diopters into the system.

Generally the WWL and WAPC are highly overrated and will not give you better optical performance than your Canon EF 8-15mm fisheye, even when combined with 1.4x or 2.0x teleconverters.

You already own the best for super wide.

Your dome choice should be taken very carefully so. Closely checking my files from 2 years diving with this rig I now find that my shots with the compact 140 fisheye dome are better that those with a superdome 9inch sized dome.

You really need a full sphere for this.

It might be worthwhile to get an adapter for your old Seacam Fisheye dome, if you own one.

Having said all the above. I shoot Canon RF and instead of Nauticam, I use a Marelux housing with which I am very pleased. I think it‘s the better Nauticam with some improvements in the small details.

15 hours ago, waso said:

And btw: is there a WA lens recommended to the 8.5" Acrylic Dome?

Or does anyone have completely different considerations regarding excellent WA IQ?

Btw: I own a RF 14-35/4 and still have the EF 8-15/4, of course.

I'll definitely buy a Super Dome later at least for split or wreck shots...

Well you already own the RF14-35 and a 8.5inch dome?!? Search no further! Just combine this excellent underwater lens with your dome (superdome had 9inch). Also the lightweight acrylic dome will be much more rewarding for split shots.

Looks like you have everything you need right in front of you. Just get a zoom gear for the 14-35 and try to measure down the the perfect extension Ring with dome data and entrance pupil position on optical bench hub.