How is aperture value affected by WWL/WACP?

[Architeuthis]

I am wondering whether there is information how WWL/WACP water contact optics affects aperture value: When using a teleconverter, because the focal length is changed by the TC and the absolute diameter of the aperture opening remains the same, the aperture number (focal length/aperture diameter) multiplies accordingly (e.g. 2x and 1.4x with appropriate TCs). Nauticam homepage says that WWL/WACP multiplies focal length by 0.36x. Does this mean it acts like a speed booster and apertures values of e.g. the Sony 28-60mm f/4-f/5.6 becomes f/2-f2.8 at the extreme ends? A photo taken with WWL/WACP at f/8 of the lens would be in fact taken at f/2.9??

 

Wolfgang

[Guest]

2 hours ago, Architeuthis said:

I am wondering whether there is information how WWL/WACP water contact optics affects aperture value: When using a teleconverter, because the focal length is changed by the TC and the absolute diameter of the aperture opening remains the same, the aperture number (focal length/aperture diameter) multiplies accordingly (e.g. 2x and 1.4x with appropriate TCs). Nauticam homepage says that WWL/WACP multiplies focal length by 0.36x. Does this mean it acts like a speed booster and apertures values of e.g. the Sony 28-60mm f/4-f/5.6 becomes f/2-f2.8 at the extreme ends? A photo taken with WWL/WACP at f/8 of the lens would be in fact taken at f/2.9??

 

Wolfgang

I have not really looked into this however I would think this is not the same of a focal reducer because the image is not straight.

In fact the 0.36x is not an accurate figure it is simply a proxy for a diagonal field of view of a rectilinear lens

If you were looking at a fisheye optic this factor would be a much smaller 20/28=0.71x

Does this give half stop benefit? In terms of light? I do not think so

[ChipBPhoto]

4 hours ago, Architeuthis said:

e.g. the Sony 28-60mm f/4-f/5.6 becomes f/2-f2.8 at the extreme ends? A photo taken with WWL/WACP at f/8 of the lens would be in fact taken at f/2.9??

 

Hi Wolfgang,  

 

This is completely un-scientific, but here are some images for comparison.  You can see FoV, DoF, and brightness differences between them.  The camera body is in the same position for both images. 

 

Lens:  Sony 28-60 at 28mm  (manual, f/8, ISO 1250, 1/10)

 

First image:  Behind a WACP-C

Second image:  Lens only  

 

I'll let someone else do the actual math. 😀 

 

 

Edited February 16 by ChipBPhoto

[Guest]

1 hour ago, ChipBPhoto said:

 

Hi Wolfgang,  

 

This is completely un-scientific, but here are some images for comparison.  You can see FoV, DoF, and brightness differences between them.  The camera body is in the same position for both images. 

 

Lens:  Sony 28-60 at 28mm  (manual, f/8, ISO 1250, 1/10)

 

First image:  Behind a WACP-C

Second image:  Lens only  

 

I'll let someone else do the actual math. 😀 

 

 

Water contact optics work differently in water hence the name

most of those adapters are afocal

[Architeuthis]

11 hours ago, ChipBPhoto said:

 

Hi Wolfgang,  

 

This is completely un-scientific, but here are some images for comparison.  You can see FoV, DoF, and brightness differences between them.  The camera body is in the same position for both images. 

 

Lens:  Sony 28-60 at 28mm  (manual, f/8, ISO 1250, 1/10)

 

First image:  Behind a WACP-C

Second image:  Lens only  

 

I'll let someone else do the actual math. 😀 

 

 

 

 

 

This is an interesting comparison. I believe the comparison could be valid if a WA (or better fisheye lens) with similar angle of view is taken and compared WACP-C (as Massimo says UW, but also over the water will give a hint (who of us is going to take the equipment UW, just to answer such a crazy question?😁)). Then one may be able to find out to which extend the aperture number is changed by the WACP/WWL...

I think aperture value is altered for sure, as AOV and focal length change and this change is in favor of WACP/WWL, but certainly not by simply multiplying with the 0.36x factor that Nauticam gives (is this even a factor for focal length or maybe the change in size of an object at a given distance or something else?)...

 

Wolfgang

Edited February 17 by Architeuthis

[Guest]

31 minutes ago, Architeuthis said:

 

This is an interesting comparison. I believe the comparison could be valid if a WA (or better fisheye lens) with similar angle of view is taken and compared WACP-C (as Massimo says UW, but also over the water will give a hint (who of us is going to take the equipment UW, just to answer such a crazy question?😁)). Then one may be able to find out to which extend the aperture number is changed by the WACP/WWL...

I think aperture value is altered for sure, as AOV and focal length change and this change is in favor of WACP/WWL, but certainly not by simply multiplying with the 0.36x factor that Nauticam gives (is this even a factor for focal length or maybe the change in size of an object at a given distance or something else?)...

 

Wolfgang

The adapter is afocal so it has a focal lenght of infinity. I think is more where the focus point is place than an issue of depth of field.

In fact most times I shoot video in manual and everything is in focus hence the whole point about CAF with those adapters is totally mooth