New Olympus 8-25mm - any takers?

[aquaticexplorer 5]

I just got my Olympus 8-25 F4 lens.  I am planning to use it underwater.  I had the PPZR-EP06 zoom gear for the Olympus 7-14mm and it fits.  I have the Olympus PPO-EP02 dome port but it was so short so I added two AOI 22mm extensions on to it and it works great.  I have not tries it underwater yet but I have no vignette at 8 mm and it still focuses throughout the whole zoom range.  Here are some Pics.

 

 

 

Edited April 25, 2022 by aquaticexplorer
Pictures split message.

[ChrisRoss 150]

6 hours ago, aquaticexplorer said:

I just got my Olympus 8-25 F4 lens.  I am planning to use it underwater.  I had the PPZR-EP06 zoom gear for the Olympus 7-14mm and it fits.  I have the Olympus PPO-EP02 dome port but it was so short so I added two AOI 22mm extensions on to it and it works great.  I have not tries it underwater yet but I have no vignette at 8 mm and it still focuses throughout the whole zoom range.  Here are some Pics.

 

 

 

Be interesting to see some results.  Focusing in air won't be a problem, it's only when the dome is in water that the focus capability is put to the test.  You could probably test it in a moderate depth tub, just dipping the dome in to test focus.  I would guess that the PPO-EP02 port might be a little small to get good corner sharpness but should improve as you zoom in.  The PPO-E04 port is a bigger port and should have better corners at the widest settings. 

I found the other day that Seacam have listed the 8-25mm on their port charts and for their ports they recommend 15-20mm more extension than the 7-14mm lens. So adding 22mm to the extension you use for the 7-14 lens should be about right.

[aquaticexplorer 5]

The Olympus 8-25mm underwater. I used the 7-14mm zoom gear with the Olympus PPO-EP02 dome port with two 22mm AOI extension rings. Here is a pic at 8mm and another at 25mm. I think it works pretty good so far. Quick and accurate focus

[Architeuthis 138]

It is time to warm up this tread: I gave a Zuiko 8mm - 25mm to my wife as birthday present and as a result I am now in charge of selecting the right extension for our next trip (she will use the lens with EM5II, Nauticam housing & Zoomgear and the Zen DP170 (N120 version)). Please tell me what you think about my considerations...

We will leave on Saturday, 19.11., to Egypt...

Unfortunately Zen does not list the 8mm - 25mm in their port charts. Hence I made a comparison between Nauticam port charts and their 180 domeport (this has the same radius of curvature as the Zen DP170, but is a little larger section of the same sphere) and the Zen port charts for DP170 and for identical lenses. The result can be seen here:

Interestingly, the difference in the overall extension is not always identical (rightmost column of the table) as I was expecting...

As Nauticam gives the right extension for the Zuiko 8mm - 25mm, I calculated the appropriate extension for two scenarios: +7mm difference (as for the Zuiko 9-18mm) and -10mm (as for Pana 8-18). The calculated extensions are shown in red (for both the 34,7mm N85-N120 adapter and the 60mm N85-N120 adapter, as we have both):

We just tried in our livingroom at which extension vignetting would occur at 8mm, but could not find any with the 60mm N85-N120 adapter plus 35mm extension (and even not with 50mm extension).

I believe that the longest possible (i.e. without vignetting) extension will result in optimum image quality, as the Zen DP170 does not allow correct positioning of the entrance pupil at 8mm as it is a too small section of the sphere for this AOV. But my wife already said she refuses to take the 50mm extension as the setup is too unhandy then (woman... )...

=> As a result we will take the 35mm extension (inbetween the two calculated ones).

 

=> I would be interested what you think is the right extension, especially from the ones that are using already this lens, but also in general...

 

Maybe I will try out also 50mm and 20mm, when she goes for macro and lens and domeport are available. I will report in december...

 

Wolfgang

Edited November 17, 2022 by Architeuthis

[Interceptor121 713]

It is time to warm up this tread: I gave a Zuiko 8mm - 25mm to my wife as birthday present and as a result I am now in charge of selecting the right extension for our next trip (she will use the lens with EM5II, Nauticam housing & Zoomgear and the Zen DP170 (N120 version)). Please tell me what you think about my considerations...
We will leave on Saturday, 19.11., to Egypt...
Unfortunately Zen does not list the 8mm - 25mm in their port charts. Hence I made a comparison between Nauticam port charts and their 180 domeport (this has the same radius of curvature as the Zen DP170, but is a little larger section of the same sphere) and the Zen port charts for DP170 and for identical lenses. The result can be seen here:

Interestingly, the difference in the overall extension is not always identical (rightmost column of the table) as I was expecting...
As Nauticam gives the right extension for the Zuiko 8mm - 25mm, I calculated the appropriate extension for two scenarios: +7mm difference (as for the Zuiko 9-18mm) and -10mm (as for Pana 8-18). The calculated extensions are shown in red (for both the 34,7mm N85-N120 adapter and the 60mm N85-N120 adapter, as we have both):

We just tried in our livingroom at which extension vignetting would occur at 8mm, but could not find any with the 60mm N85-N120 adapter plus 35mm extension (and even not with 50mm extension).
I believe that the longest possible (i.e. without vignetting) extension will result in optimum image quality, as the Zen DP170 does not allow correct positioning of the entrance pupil at 8mm as it is a too small section of the sphere for this AOV. But my wife already said she refuses to take the 50mm extension as the setup is too unhandy then (woman... )...
=> As a result we will take the 35mm extension (inbetween the two calculated ones).
 
=> I would be interested what you think is the right extension, especially from the ones that are using already this lens, but also in general...
 
Maybe I will try out also 50mm and 20mm, when she goes for macro and lens and domeport are available. I will report in december...
 
Wolfgang

Depending on the arc that the dome hosts you can calculate the maximum field of view
If this is smaller than the lens field of view the vignetting criteria is correct
If instead the dome is a full hemisphere then you need to position the lens nodal point in the centre of the dome
I don’t think the zen170 is an hemisphere


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[ChrisRoss 150]

6 hours ago, Architeuthis said:

We just tried in our livingroom at which extension vignetting would occur at 8mm, but could not find any with the 60mm N85-N120 adapter plus 35mm extension (and even not with 50mm extension).

I believe that the longest possible (i.e. without vignetting) extension will result in optimum image quality, as the Zen DP170 does not allow correct positioning of the entrance pupil at 8mm as it is a too small section of the sphere for this AOV. But my wife already said she refuses to take the 50mm extension as the setup is too unhandy then (woman... )...

=> As a result we will take the 35mm extension (inbetween the two calculated ones).

 

=> I would be interested what you think is the right extension, especially from the ones that are using already this lens, but also in general...

 

Maybe I will try out also 50mm and 20mm, when she goes for macro and lens and domeport are available. I will report in december...

 

Wolfgang

Seacam lists this lens in their port charts and they are recommending 15-20mm more extension than the 7-14 lens.  The port chart is here:

http://www.seacam.fr/telechargements/ports-panasonic-olympus-en.pdf

Using the difference between known extensions is probably as good a way as any to sort out which extension to use.  Double check by physically installing the lens on land to check you are not vignetting and then give it a try.

[Architeuthis 138]

Thank you Chris and Massimo, for your interesting comments (as always)...

Here is a table of maximal diagonal AOVs (when correct positioning is required) and the corresponding focal lengths (FF equivalent, so it is half for MFT) for different domeports, calculated just from their geometry and the (sparse) data that I found about the ports:

 

In fact Zen 170 starts at 18mm (9mm for MFT), so the maximum extension possible without vignetting would (theoretically!) be the optimum...

The problem with comparing the differences for extensions is that they are not always identical between companies. When calculating from the difference between Zuiko Pro 7-14 and Zuiko Pro 8-25 from the Nauticam chart, one arrives at an additional extension of 40mm for the 8-25. Add this to the extension of 80mm recommended by Zen for the 7-14 and one ends up with 120mm of total extension (as I wrote 60mm+50mm does not vignette)...

=> I will test the maximum extension possible on a dive (indeed a hughe setup!)) and compare to the 60+35mm that Lisi will be using - lets see whether there is a real life difference...

 

Wolfgang

 

Edited November 18, 2022 by Architeuthis

[ChrisRoss 150]

1 hour ago, Architeuthis said:

Thank you Chris and Massimo, for your interesting comments (as always)...

Here is a table of maximal diagonal AOVs (when correct positioning is required) and the corresponding focal lengths (FF equivalent, so it is half for MFT) for different domeports, calculated just from their geometry and the (sparse) data that I found about the ports:

 

In fact Zen 170 starts at 18mm (9mm for MFT), so the maximum extension possible without vignetting would (theoretically!) be the optimum...

The problem with comparing the differences for extensions is that they are not always identical between companies. When calculating from the difference between Zuiko Pro 7-14 and Zuiko Pro 8-25 from the Nauticam chart, one arrives at an additional extension of 40mm for the 8-25. Add this to the extension of 80mm recommended by Zen for the 7-14 and one ends up with 120mm of total extension (as I wrote 60mm+50mm does not vignette)...

=> I will test the maximum extension possible on a dive (indeed a hughe setup!)) and compare to the 60+35mm that Lisi will be using - lets see whether there is a real life difference...

 

Wolfgang

 

I'm not sure where the numbers come from, but I see for the seacam compact port the extension for 7-14 is 40mm and the 8-25 is 60mm, so that says you should look at 20mm more extension for the 8-25 compared to the 7-14.  Which would be 75mm total extension if I'm not mistaken.  I see also Nauticam now has the 8-25 on their port chart and they ask for 94 or 95mm extension with the 180mm dome.  for some reason Nauticam want to use about 20mm more extension.  The compact port seems to have similar properties to the Zen dome.

Of course if you have the gear already a test is the way to go.

[Architeuthis 138]

Here I am back from diving holidays in Egypt... 

I had the opportunity to test out the Zuiko 8-15mm f 4.0 lens with Oly Em1II and Zen DP170. I was able to test the 60mm+30mm extension and also the 60mm+50mm extension. Both did not vignette and from theory (see above), the 60mm+50mm should perform better. Above the water in our room, I also tested a 60mm+65mm extension, but this one did slightly vignette in the corners. I guess that 60mm+55mm and MAYBE also 60mm+60mm should be possible without vignetting. I must say that the rig gets more and more monstrous, the longer the extension becomes and there must be a good reason (i.e. clearly superior IQ) that one takes this burden...

As already stated by the others, the 8-25 Pro lens is very good in IQ and the zoom range from 8mm to 25mm is fantastic. In order to see which apertures will give good IQ (especially in the corners) and whether the length of extension has a noticeable influence, I took two series of bland riffscapes. As I was floating freely the framing is not exactly identical between different apertures. Also the reefscape is not a 2D test poster, but in 3D, what also complicates the interpretation. Nevertheless I believe the images allow some crude judgement what is acceptable and what not:

Here the entire, uncropped, image taken with the 60mm+35mm extension @8mm, 1/60s, 2* Z330 (f 7.1):

 

 

And here the entire, uncropped, image taken with the 60mm+50mm extension @8mm, 1/400s, 2* Z330 ( (f 7.1):

 

I cropped the images and the series below shows the left, lower, corners of the two series taken (f 7.0 is not exact, it should be 7.1, actually):

 

From the images I conclude that starting from f 7.1 the corners are o.k. The different extensions did not make a substantial difference (not substantial enough at least). When light is essential one may even go to f 5.6. What do you think? Interested to read your comments...

 

Wolfgang

 

Edited December 7, 2022 by Architeuthis

[Interceptor121 713]

Am not impressed by either
I think the dome maybe to small the edges are warping
This lens extends a lot while zooming and that will mean only a few focal length will be ideally in position and the rest will progressively have more distortion
I like my panasonic lens with internal zoom better


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[ChrisRoss 150]

The lens actually doesn't move that much when zooming, it makes a big change in length to get from working position to the widest setting where it grows by 28mm but that's not relevant to dome positioning as it just moving the lens to working position.  Once it is open it changes length by a total of 9mm between min and max zoom, it actually retracts as it zooms in to about 19mm then extends slightly again.  This characteristic is quite good for vignetting as it extends the maximum at its widest.  As to the the impact of the change in length 9mm change doesn't seem like much - though the entrance pupil may or may not move a little more than that.   My 12-40mm gives great performance and the entrance pupil on that moves backwards even though the lens extends. 

As to the lens if I were using it based on this test I think I'd set at f8 and leave it there unless I needed more light.

[Wapiti 25]

I tried this lens with an M1mkIII, AOI housing, and the same Inon 170mm dome that I used successfully with the 12-40 with that camera  and housing, as well as with the  M1mkI, Panasonic 8-18, and Oly 7-14 in the Oly housing.  The 8-25 had horrible corners at 8mm, up until f8 where they became barely acceptable, similar to the above shots.  Pretty disappointing, to be honest as it meant no ultra wide (weitwinkel) angle for a recent trip to British Columbia where we experienced better viz than we had any right to expect.  The PL8-18 was great with the 170mm but it won't work in the M1mkIII / OM-1 AOI housings because of the way the zoom gear has to mount (they natively take PEN ports but can be adapted to OMD ports).  I just acquired the 8" dome that AOI recommends, and I'll give it a shot this weekend. 

I do like the range of the 8-25 but it kinda figures that I had to do the typical underwater photography upgrade cluster:  new camera and housing?  Favorite lens won't work, so buy a new one.  New lens won't work in your hard earned glass dome, so buy a new one.  Rinse and repeat   Here's a shot from my test dive with the 8-25 in my 170mm dome- 19mm, and cropped.