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Canon 8-15 - teleconverter


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Hi all,

I thought this forum really needs a thread about using the Canon 8-15 with teleconverters, wouldn't be complete without 😄

 

I was thinking about getting the Sony 2.0x as an addition (thanks to @Gudge I can use the Sony teleconverter with my setup), but I'm not sure about the optical quality behint the Nauticam 140mm domeport. Has anyone used a 2.0x teleconverter with it underwater and can share his experience with the image quality?

I expect to be the range from 16 to 30mm quite interessting. I'd only lose 1mm towards the 15mm fullframe fisheye, but would gain from 21mm (as with the 1.4x TC) 9mm towards the 30mm.

 

Thanks!

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58 minutes ago, Interceptor121 said:

I would not recommended 2x tc

 

Thank you @Interceptor121. I remember your articels from "the old WP", I found them very helpful. I do like the 1.4x TC (Sony, not Kenko) very much, but I'm still unsure about the 2.0x TC. Why do you not recommend it?

I would love to just give it a try, maybe I can rent the 2.0x TC for a couple of days and try it out underwater. Otherwise, I might only be able to take a couple of test shots outside, but I'm afraid that this is not enough to judge the IQ.

 

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1 hour ago, Fabian said:

 

Thank you @Interceptor121. I remember your articels from "the old WP", I found them very helpful. I do like the 1.4x TC (Sony, not Kenko) very much, but I'm still unsure about the 2.0x TC. Why do you not recommend it?

I would love to just give it a try, maybe I can rent the 2.0x TC for a couple of days and try it out underwater. Otherwise, I might only be able to take a couple of test shots outside, but I'm afraid that this is not enough to judge the IQ.

 

All 2x tc invariably on any format degrades image quality 

with regards to using a sony tc I have the 1.4 and the kenko

placing the tc before the adapter results in wrong distance and higher than 1.4x magnification hence I would recommend buying a kenko and not using the sony though technically it seems to work in any case

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On 2/15/2024 at 10:58 AM, Fabian said:

Hi all,

I thought this forum really needs a thread about using the Canon 8-15 with teleconverters, wouldn't be complete without 😄

 

I was thinking about getting the Sony 2.0x as an addition (thanks to @Gudge I can use the Sony teleconverter with my setup), but I'm not sure about the optical quality behint the Nauticam 140mm domeport. Has anyone used a 2.0x teleconverter with it underwater and can share his experience with the image quality?

I expect to be the range from 16 to 30mm quite interessting. I'd only lose 1mm towards the 15mm fullframe fisheye, but would gain from 21mm (as with the 1.4x TC) 9mm towards the 30mm.

 

Thanks!

 

Hi Fabian,

 

I did not use a 2x TC UW so far, but I have both Kenko 1.4x and 2x and the Canon 8-15mm fisheye lens. To be precise these are (there are different models around): #1.: Kenko C-AF 1.4x Teleplus Pro 300 and the #2.: 2x Teleplus HDpro.

 

I do use the 1.4x UW with the Canon 8-15mm with Sony A7R5. As Massimo writes in his reviews, IQ is o.k. with 1.4x TC. I. personally, find the usable range of 15-21mm a bit small, but better than nothing...

 

I once bought the 2x TC and tested it on a grill party at home with the Canon 8-15mm (but this was with the MFT camara, an Olympus EM1II that I had then). The photos were so low contrast that I did not further test for UW use...

 

Instigated by your question, I just went out with my A7R5 and made some over-the water photos with Canon 8-15mm, without TC and with 1.4x and 2x TCs. I think this should give an impression of the overall IQ and whether it makes sense to test out further UW...

 

I tested at the extreme focal lengthes at different aperture values and changed the object distance to make the test chart, more or less, fill the frame...

 

Here first three uncropped photos w/o and with 1.4x and 2x TCs at the extreme focal lengths and aperture "wide" open:

 

w/o TC; 14mm; f/4.0:

14mm_wo_14mm_f4.jpg

 

 

1.4x TC; 21mm; f/5.6:

1.4x_21mm_f56.jpg

 

 

2x TC; 30mm; f/8.0:

2x_30mm_f8.jpg

 

In subsequent post(s) I will show comparable crops of the central part of the image at different settings...

 

Wolfgang

Edited by Architeuthis
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Here come now some cropped sections from the center. I think the corners do not make sense with fisheye lenses (it has a reason why serious test sides do not measure resolution performance of fisheye lenses), but UW and behind domes the corners of fisheye lenses are always good compared to rectilinear. Note also that the ratio of the image heigth of the glued in and printed out test chart is ROUGHLY around 3,5x, so the numbers in the test chart need to be multiplied with 350 to give resolution in lines/image heigth. Due to the print out process numbers between 1 (= approx. 350 lines/IH) and 6 (= 2100 lines/IH) make sense, sometimes one could go as far as 8 (= 2800 lines/IH). 2800 l/IH may not seem much with precious lenses and modern cameras, but many here doubth that such resolutions can be achieved UW, because of the diffraction of light in water and by the particles and/or solutes in water etc. ...

 

Here the first series, again "wide" open, but at the shortest possible focal lengthes:

 

w/o TC; 14mm; f/4.0:

14mm_wo_f4.jpg

 

 

1.4x TC; 14mm; f/5.6:

14mm_14x__14mm_f56.jpg

 

2x TC; 16mm; f/8.0:

14mm_2x_16mm_f8.jpg

 

More to come...

Edited by Architeuthis
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And here another series, at comparable and close to real life aperture of f/8.0, but at the widest end possible for each combination:

 

w/o TC; 14mm; f/8.0:

14mm_wo_f8.jpg

 

 

1.4x TC; 21mm; f/8.0:

14mm_14x__21mm_f8.jpg

 

 

2x TC; 30mm; f/8.0:

14mm_2x_30mm_f8.jpg

 

I am eager to hear what you people think and how you would rate IQ. If wantes, I can also show other series...

Maybe I will take the 2x TC once UW, just to have real life pictures, but my expectation is that it is not really worth going for it...

 

 

Wolfgang

 

P.S.: My personal rating is that the pure resolution of the combinations is good in all cases, but the photos get more and more "mushy", the more TC is used (worsening of microcontrast?)...

Edited by Architeuthis
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4 minutes ago, Barmaglot said:

The 2x TC sample doesn't really look that bad. Am I correct in assuming that with 2x TC, the wide end of the zoom range is equivalent to the narrow end of the bare lens, i.e. 180 degree diagonal?

Yes, with the 2x TC, 16mm are derived from adjusting 8mm at the lens itself...

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Thank you @Architeuthis! Really appreciate your effort!

 

If you ever take it underwater, I'm curious to see some real life examples 😉

 

For me, the 2.0x doesn't look to bad. At a 100% crop pictures will be less clear than with a 1.4 or bare lens, but I still find it really interessting for dive where I might encounter bigger and shy animals. Lets see, but looks like I found a reason to buy more stuff 🙂 as I always explain to my wife: Haben ist besser als Brauchen. ("to have is better than to need")

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Here is another series, same photos at higher magnification, the results are surprising to me:

 

w/o TC; 14mm; f/4.0:

wox_14mm_f4_crop.jpg

 

 

1.4x TC; 14mm; f/5.6:

1.4x_14mm_f56_crop2.jpg

 

 

2x TC; 16mm; f/8.0:

2x_16mm_f8_crop.jpg

 

 

Above the three combinations, all at focal length to give approx 180° diagonal. Here a similar crop from the 2x combination at the long end:

2x TC; 30mm; f/8.0:

2x_30mm_f8_crop.jpg

 

 

=> The surprise to me is that the 1.4x TC performs worst. First thought was, that the photo is blurry, because out of focus. I made, however, two independent photos and they look similar. Also the structure of the blank paper itself, without the printing, looks in focus and just alike the other photos. It is just the transition from black to white that gets more blurred with the 1.4x (I guess this transition is, to some extend, a measure of microcontrast?). I am quite sure that  all photos are in focus, but will try to make another series in the future, just to check...

 

 

What may be the reason?

 

My guess:

#1.: The photos with different TCs, but all at approx. 180° diagonal, are obtained at different focal length of the original lens. The performance of a zoom lens is very well known to depend on focal length used...

#2.: The 1.4x TC was the first that I bought and it is not the highest quality available (the HD pro grade was not available at the time of purchase), while the 2x TC is the highest grade ("HDpro")...

 

 

Wolfgang

 

Edited by Architeuthis
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1 hour ago, Architeuthis said:

Here is another series, same photos at higher magnification, the results are surprising to me:

 

w/o TC; 14mm; f/4.0:

wox_14mm_f4_crop.jpg

 

 

1.4x TC; 14mm; f/5.6:

1.4x_14mm_f56_crop2.jpg

 

 

2x TC; 16mm; f/8.0:

2x_16mm_f8_crop.jpg

 

 

Above the three combinations, all at focal length to give approx 180° diagonal. Here a similar crop from the 2x combination at the long end:

2x TC; 30mm; f/8.0:

2x_30mm_f8_crop.jpg

 

 

=> The surprise to me is that the 1.4x TC performs worst. First thought was, that the photo is blurry, because out of focus. I made, however, two independent photos and they look similar. Also the structure of the blank paper itself, without the printing, looks in focus and just alike the other photos. It is just the transition from black to white that gets more blurred with the 1.4x (I guess this transition is, to some extend, a measure of microcontrast?). I am quite sure that  all photos are in focus, but will try to make another series in the future, just to check...

 

 

What may be the reason?

 

My guess:

#1.: The photos with different TCs, but all at approx. 180° diagonal, are obtained at different focal length of the original lens. The performance of a zoom lens is very well known to depend on focal length used...

#2.: The 1.4x TC was the first that I bought and it is not the highest quality available (the HD pro grade was not available at the time of purchase), while the 2x TC is the highest grade ("HDpro")...

 

 

Wolfgang

 

The canon 8-15mm is sharper at 8mm than it is at 15mm

 

This why at 15mm the tc 1.4 is very similar to the bare lens

 

I do not own the old teleconverter version I have the newer HDPro kenko version 1.4 however looking at your samples you were closer with the 1.4 tc and as you do get close the lens drops performance a little the image also looks somewhat soft

 

Having said that the 2x images do not look that bad at all and a new 2x converter is £169 so I might try this one

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19 hours ago, Architeuthis said:

Yes, with the 2x TC, 16mm are derived from adjusting 8mm at the lens itself...

So in conclusion, with Kenko Teleplus HD Pro 2x, the Canon (and, by extrapolation, Nikon) 8-15mm gives a similar, or slightly greater, zoom range than Tokina 10-17mm on APS-C/DX cameras, correct? 

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4 hours ago, Barmaglot said:

So in conclusion, with Kenko Teleplus HD Pro 2x, the Canon (and, by extrapolation, Nikon) 8-15mm gives a similar, or slightly greater, zoom range than Tokina 10-17mm on APS-C/DX cameras, correct? 

Yes. Canon 8-15mm gives 16-30mm when used with 2x TC (15-21mm are usable when paired with 1.4x TC). There are small differences between DX (1.5x) and Canon APS-C (1.6x). Hence the Tokina gives the same angle of view as 15-25.5mm (DX) and 16-27mm (Canon APS-C ) would give on FF. Sony APS-C has crop factor of 1.5x, like DX...

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Here I have more example photos: First some kind of "reference": a closeup of approx. the closest crop area in order to see what blurr is caused by the printer and not by the lenses. The photo was made with the Sony 90mm macro lens.

 

Closeup: Sony 90mm G macro; f/9.0:

macro_90mm_f9_crop.jpg

 

=> Any irregularity in the lines and blurriness comes now from the laserprinter. We can see that the resolution lines are usable up to the number of 11, i.e. roughly 3850 lines/image heigth in the test settings used (what is pretty good).

 

Then I made a test photo under the test setting (=entire test chart with three resolution charts fills, more or less, the frame) with the presumably best lens that I have and made an extreme crop of the central area (this area, is indeed and extreme crop, the length of the zoomed in image is approx 570 pixels)...

 

Sony 50mm f/1.2 GM; f/4.0:

GM12_50mm_f4_crop.jpg

=> this is supposed to be a very good resolution/microcontrast...

 

And this is now compared to the Sony 28-60mm, that I will use soon behind the WACP-C. Just the bare lens, but I guess the resolution will not increase because of the WACP-C, but the high quality water contact optics will likely also not male it worse :

 

Sony 28-60mm 28mm; f/4.0:

FE2860_28mm_f4_crop.jpg

 

Sony 28-80; f/8.0:

FE2860_28mm_f8_crop.jpg

 

And here the 28-60mm lens, but zoomed in:

 

Sony 28-60mm; @60mm; f/5.6:

FE2860_60mm_f56_crop.jpg

 

 

=> Interested to hear what you say about this little test and how you rate central sharpness compared to the fisheye with and without TCs...

 

Wolfgang

 

FE2860_60mm_f8_crop.jpg

Edited by Architeuthis
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OK, that's it, I'm taking the bullet here. I bought the Sony 2x teleconverter. As the 2x is longer than the 1.4x, I need a different extension (already ordered) and will have to modify the 3D model for the zoom gear. This might take a while as I never did anything with 3D design, but on land the zoom range already looks promising with the Canon 8-15mm.

Now - any recommendations to learn "3D design for underwater photography"? 🙂

Once everything works I'll share some pictures for a real life evaluation here, but might take a while, depending on how quick I get a hang of this 3D stuff.

 

Different idea: how about a database for port setups like this? I.e. listing lens, adapters, ports, housings, extensions and (most importantly) pictures that allow to judge the optical quality? Figuring out setups is a pain, and being able to dig into what other people tried and found to be working would be awesome. I feel like the admins are soon gonna be annoyed with all my ideas, but if not and you'd like to discuss more about it, always happy to 😇

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Thanks @Barmaglot, I was more looking into the overall port setup (e.g. "Sony A7IV housing - 35.5mm N100 N120 adapter - 55mmm (25mm+30mm) N120 extensions -  N120 140mm glass domeport domeport - custom zoom gear) for this kind of database

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That's reasonably easy to work out from the existing charts - the 2x converter is 40mm long, so just add 40mm of extension, i.e. Nauticam recommends 35.5mm N100 to N120 adapter + 30mm extension ring + 140mm dome for the bare lens, so by adding a 40mm extension ring (#22140) or using a single #22170 for a total of 70mm of extension you should have the lens and dome in the same alignment.

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This might be true for the one selected example, but not for all lenses / combinations you can find a port chart to start with, hence all the threads on wetpixel about setups, and those threads will start here as well.

Additionally, some dimensions are not easy to or even impossible to find online e.g. interflange dimensions for teleconverters. If you look online for the Sony 2x TC, it's length is given at 42.7mm. The actual interflange distance is 27.something mm. Next part is: does the protrusion work with the lens/fit inside? So there is a bit more to it than just looking up the length...

 

Yes, one can buy, measure, trying to figure out if you can get the required parts to match the setup. Requires an investment to start with any idea...

Or, and that would be my preferred solution, look up what other people did with a given lens, judge the optical quality from some 100% crops and decide if it's good enough to order the parts...

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1 hour ago, Fabian said:

OK, that's it, I'm taking the bullet here. I bought the Sony 2x teleconverter. As the 2x is longer than the 1.4x, I need a different extension (already ordered) and will have to modify the 3D model for the zoom gear. This might take a while as I never did anything with 3D design, but on land the zoom range already looks promising with the Canon 8-15mm.

Now - any recommendations to learn "3D design for underwater photography"? 🙂

Once everything works I'll share some pictures for a real life evaluation here, but might take a while, depending on how quick I get a hang of this 3D stuff.

 

Different idea: how about a database for port setups like this? I.e. listing lens, adapters, ports, housings, extensions and (most importantly) pictures that allow to judge the optical quality? Figuring out setups is a pain, and being able to dig into what other people tried and found to be working would be awesome. I feel like the admins are soon gonna be annoyed with all my ideas, but if not and you'd like to discuss more about it, always happy to 😇

As Barmaglot says, the extension for the Nauticam zoomgear needs to be 40mm (other parameters remaining equal). I have a 3D file for such an extension printed and added it to the other extensions: https://www.dropbox.com/scl/fi/ihczuhycokiyjdyja2a13/Canon_815_2xKenko.stl?rlkey=wx5slo4sb2evhd43h81wkxuuk&dl=0

 

=> Before printing, check the length of the Sony 2x TC that you intend to use. It may deviate from the length of the Kenko 2x TC (i.e. 40mm) as it contains glass optics...

 

Wolfgang

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9 minutes ago, Architeuthis said:

=> Before printing, check the length of the Sony 2x TC that you intend to use. It may deviate from the length of the Kenko 2x TC (i.e. 40mm) as it contains glass optics...

 

Hi Wolfgang,

The Sony TC is built different from the Kenko, with a small protruding element. The overall length of the TC is 42.7mm, but as the interflange distance is 27mm, so the lens only moves forward 27mm and not 42.7mm.

If helpful for anyone, I'm happy to take some pictures of the dimensions to make it better to grasp. 

Best 

Fabian 

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There seems to be a difference of 9.1mm between the sony 1.4 and 2.0 therefore the latter needs 1cm more

i think buying the sony 2.0 is a bit risky on its own let alone starting building gear.

the 1.4 tc compared to the kenko has more crop already.

I would not see an issue buying the kenko as an experiment it is not expensive but buying the sony makes little sense unless you use it with a 70-200 GMII or a G master prime on land 

due to the fact the field of view differs I am not using the Sony 1.4 at first sight I saw no optical benefits in addition to the smaller field of view compared to the kenko but I have not done systematic tests. Again I have no use case for a sony 2x TC and it is expensive to just use with the canon and risky so in case I will just get a kenko 2.0

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I've seen mentions - no personal experience, mind you - that Sony blocks the use of their teleconverters with third party lenses. This was in the context of Sigma/Tamron E-mount telephotos, but if that is true, I can see an EF-mount lens on Metabones/MC-11 getting blocked as well. Considering that a Sony 2x TC costs $550 while a Kenko one costs $300, the choice seems pretty clear.

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