Canon EF 8-15mm Fisheye Questions

[Interceptor121 712]

4 minutes ago, Alex_Mustard said:

I have a Metabones adaptor. I have not tried others.

I only have 3 lenses with the Sony A7RV I have here. The 28-60mm with the WWL/WACP definitely focuses much better than my reference Nikon 28-70mm with WACP on D850. The 90mm is much better at tracking fish than the Nikon 105mm. Although the 90mm is less impressive at smaller macro and looses its advantage over the 105mm/D850 combo.

However, the 8-15mm Canon/Metabones does not focus as well as the Nikon 8-15mm on D850. When both are confident, they both snap onto the subject so instantly that there is not significant difference between them and no real point in commenting on the performance as even if one was better it would not really be worth commenting on. However, with strongly backlit, monochromatic, strange shaped subjects (as most wide angle foregrounds look to a camera underwater) the 8-15mm Canon will hunt at times. This is much more prevalent with a smaller dome port. The hunting is common enough for me to want to comment on. But while it has slowed me down shooting, I've not missed any shots. The best solution is to switch to back button/thumb focus (Focus With Shutter Off in Sony-speak) with this lens.

So overall, I find the A7RV to be the best autofocusing underwater cameras I have used. It is logical to expect the A1 to be better. But it also clearly has areas of strength, and areas of weakness. The latter really a result of Sony's poor lens availability for underwater shooting, which hopefully will be redressed. 

Alex

Alex

When you attach the metabones there is a little led on the side of the converter. It can either have blue or red color

What color is on your adapter? This can be configured and controls how focus works

[stillviking 5]

12 hours ago, Interceptor121 said:

It is not a good idea as obviously corners are very low resolution and the amount of crop becomes considerable

So in a EF 8-15 mm vs RF 16 mm battle if I want straight lines (really don't enjoy Fisheye distortion effects) maybe even RF 16 mm is better, because 15 mm corners will also have few resolution and crop will look at least 16 mm..

[Interceptor121 712]

4 minutes ago, stillviking said:

So in a EF 8-15 mm vs RF 16 mm battle if I want straight lines (really don't enjoy Fisheye distortion effects) maybe even RF 16 mm is better, because 15 mm corners will also have few resolution and crop will look at least 16 mm..

If  you want straight lines you shoot a rectilinear lens. Correcting a fisheye lens to rectilinar normally looks much worse than a rectilinear lens after you have cropped the image

A fisheye lens in my mind is for shots where you are not aware of the shape of things and the geometry 

When having real proportion is a requirement across the same you need a solution with an acceptable amount of distortion

[ChrisRoss 150]

19 hours ago, Interceptor121 said:

If  you want straight lines you shoot a rectilinear lens. Correcting a fisheye lens to rectilinar normally looks much worse than a rectilinear lens after you have cropped the image

A fisheye lens in my mind is for shots where you are not aware of the shape of things and the geometry 

When having real proportion is a requirement across the same you need a solution with an acceptable amount of distortion

Agree, using a fisheye for what it is good at the fisheye distortion is not really apparent, you do have to pick the angle you shoot from and what you include in the frame and watch the corners, but for what a fisheye is good at - a rectilinear wide is not a great substitute.  I'm talking CFWA, reef scenics and really big animals.  The rectilinear is more suited to wrecks perhaps and also comes into play when you need more reach for shier subjects, but the penalty is poor corner performance and needing a 230mm dome to do its best.

Put it another way when talking about which lens to use you really need to specify the subject matter.

[Architeuthis 138]

8 minutes ago, ChrisRoss said:

Agree, using a fisheye for what it is good at the fisheye distortion is not really apparent, you do have to pick the angle you shoot from and what you include in the frame and watch the corners, but for what a fisheye is good at - a rectilinear wide is not a great substitute.  I'm talking CFWA, reef scenics and really big animals.  The rectilinear is more suited to wrecks perhaps and also comes into play when you need more reach for shier subjects, but the penalty is poor corner performance and needing a 230mm dome to do its best.

Put it another way when talking about which lens to use you really need to specify the subject matter.

 

The example posted by Tom is not a good example as it is #1. a split shot, where the over water region is, of course, not in focus and #2.: it is CFWA, where the DOF region is thin and most of parts of the image are not in focus, even under the water. Stretching out the unsharp regions will results in complete destruction of IQ, as is shown...

In my experience, partial fisheye correction in LR does not degrade image quality. I frequently use this for images, e.g. from divers or from wrecks...

100% correction is, of course, too much - for a 180° fisheye this would equal a rectilinear WA lens with less than 1mm focal length that does not exist - I doubt that IQ would be better with such a lens if it would exist. Correction also requires a good lensprofile that is often non-existing (e.g. for WWL/WACP) and needed to be made in DIY mode...

Maybe, in order not to hijack this thread, we should open up a separate thread on fisheye correction were we post more examples and discuss in detail...

 

Wolfgang

 

[Alex_Mustard 0]

On 1/20/2023 at 12:09 PM, Interceptor121 said:

When you attach the metabones there is a little led on the side of the converter. It can either have blue or red color

What color is on your adapter? This can be configured and controls how focus works

This could definitely be a factor, but I don't know the answer. The Metabones adaptor I am using does not have a LED on it. It has a red dot on it to help line up the lens - see picture. 

I would expect it to be a good one, as my friend who has lent it to me usually has all the best gear (hence why he has a A7RV and housing to lend). Tape is to stop the lens zooming to any of the useless focal lengths!

 

[Alex_Mustard 0]

Regarding FE correction - a big issue for me is that if you plan to routinely correct fisheye shots - the compositions that are are deciding on underwater, though your viewfinder, really aren't the ones you are getting in your final shots. You are trusting a reasonably amount to guesstimates for pleasing looking framing. 

[Interceptor121 712]

This could definitely be a factor, but I don't know the answer. The Metabones adaptor I am using does not have a LED on it. It has a red dot on it to help line up the lens - see picture. 

I would expect it to be a good one, as my friend who has lent it to me usually has all the best gear (hence why he has a A7RV and housing to lend). Tape is to stop the lens zooming to any of the useless focal lengths!
 

The dot I mean shows when the adapter is on the camera and the camera is on
It is either blue or red


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[Alex_Mustard 0]

I am probably just being dumb. But I have it on the camera and I am taking photos, and I really can't see any LED on my adaptor. Can you find a picture of one online and share, so that I know what I am looking for.

[Interceptor121 712]

I am probably just being dumb. But I have it on the camera and I am taking photos, and I really can't see any LED on my adaptor. Can you find a picture of one online and share, so that I know what I am looking for.

I think your adaptor is the Mark IV
The dot is on the mark V
I will post an image when I get back
To give an idea metabones is at v70 firmware of the mark V things keep improving and the software plus the version of the adapter matter
In addition the mark V has a green and advanced mode
Some lenses like one some like the other
The key difference is how af works and how many pdaf points are available plus other useful features such display of the focal length
You are right that nailing down the best settings is essential


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[shanesmith.photos 13]

This is a really interesting thread, thanks everyone. For those of you using the Kenko teleconverter, how do you align your zoom gear with the housing’s gearing (or do you use a different zoom gear for this)? The Nauticam N100-N120 adapter has a zoom dial which is aligned to match the position of Canon lenses. Adding a teleconverter in front of the lens would put this alignment out. At least the Sony teleconverter option doesn’t mess with that.

[Interceptor121 712]

This is a really interesting thread, thanks everyone. For those of you using the Kenko teleconverter, how do you align your zoom gear with the housing’s gearing (or do you use a different zoom gear for this)? The Nauticam N100-N120 adapter has a zoom dial which is aligned to match the position of Canon lenses. Adding a teleconverter in front of the lens would put this alignment out. At least the Sony teleconverter option doesn’t mess with that.

The kenko is around 2 cm you need 20 mm extension and the special zoom gear

It doesn’t matter if you use a teleconverter before or after the adapter the zoom ring will go forward 2 cm

If you use a different teleconverter you need to recalculate the extension and the zoom gear may not work

 

 

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[shanesmith.photos 13]

Thanks @Interceptor121. With the Sony teleconverter, you could theoretically use an N100 spacer BEFORE the N100-120 adapter (i.e. Housing - N100 spacer - N100-120 - dome) to adjust for the length of the teleconverter, in which case you’d be able to use the standard zoom gear setup without any corrections (as the zoom gear mounts to a knob on the N100-120 adapter rather than the housing itself). This seems like quite a clean way to add/remove the teleconverter without having to change zoom gears, but the cost and potential image quality/focusing issues with this ordering may be more important arguments against it.

[Interceptor121 712]

Thanks [mention=34353]Interceptor121[/mention]. With the Sony teleconverter, you could theoretically use an N100 spacer BEFORE the N100-120 adapter (i.e. Housing - N100 spacer - N100-120 - dome) to adjust for the length of the teleconverter, in which case you’d be able to use the standard zoom gear setup without any corrections (as the zoom gear mounts to a knob on the N100-120 adapter rather than the housing itself). This seems like quite a clean way to add/remove the teleconverter without having to change zoom gears, but the cost and potential image quality/focusing issues with this ordering may be more important arguments against it.

I dont like the idea of putting an extension ring of smaller diameter on the housing and moving the focus lever forward


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