Sony 20-70mm f4 lens

[John E]

I think a few people use this lens as it has a versatile zoom range for mixing wide-angle and close-up on the same dive. I mainly got it for fish and people portraits but it seems a good lens for dives when I don't know what to expect. I have been using it with a close-up achromatic diopter lens. (Sigma AML-72-01) which 72mm diameter, matching the lens filter threads. I think it is 1.75 strength. 

 

To be honest I am not sure how important the diopter is, but it certainly seems sharp using it. Maybe someone else has the calculations on what it does to the minimum focus distance. I have a photo of the top of my Sony A75 with the diopter and without which shows the minimum focus distance looks slightly reduced, but not by much. I assume it helps corners at the 20mm end and maybe helps to be able use a larger aperture with an 8 inch dome. I haven't tried it in a smaller dome. Isotta have a zoom gear and port extension for this lens although it is not yet listed on their Sony port chart.

 

The replicated close-up pictures are just crops of the original frame. Of course for wide angle it is not as possible to get as close as an ultrawide lens to the subject but in clear water it is still effective.

 

 

Edited August 22 by John E
typing mistake

[humu9679]

@John E I’ve used it with a 180mm dome with good results. An excellent general purpose range that focuses close on its own. I’ve since moved on to the WWL-1 for wide. 

[dentrock]

Finally got to test mine this morning with A7RV and Nauticam, and following the N port chart recommendation (35 adap + 35 ext + N120 180 dome).

In addition to Phil Rudin's positive reports:

Positives:

1. At 20, focuses to within approx 50 mm from dome.

2. At 70, approx 65-75 from dome. Specs say 1:2.6 max mag; MFD 30cm at 20 to 25cm at 70, so N recommendation is sound.

3. Heavy rig on land but quite well balanced UW.

4. Successfully shot 40mm gobies as well as a bit of boring WA in the conditions.

5. Very sharp for close-ups and fast focus. As sharp as my macro lenses on gobies.

6. Corners pretty good (no complaints from me, but obsessives can obsess). Besides, for WA I rarely shoot with smaller ap than f8.

7. Zoom is operated by the housing knob and gear. No need for adapter with knob.

8. Terrific lens for general use on land.

 

Negatives:

1. As above, rig is very heavy on land at 5913 g, excluding strobes and arms. Actually, shocked me coming from APS-C A6400 rig. Not ideal for shore dives, depending on difficulty of entry.

Options to reduce weight include:

a) shoot with A7CR (1.1 kg lighter, comprising 200 less for body and 900 less for housing)

b) try with 140 dome (save another 500g). Will do so weather permitting.

2. 35mm adapter used as recommended, but adapter knob gets in the way of housing knob. Because of the profile of the housing face (not flat), cannot mount upside down to get the knob out of the way.

What was Nauticam thinking??????

If I was buying the bits to use this lens again, I'd use the hideously expensive 25mm adapter (no knob) + 50mm N100 ext.

Or if I owned the N100 version of the 180 dome, no need for adapters. Just use extensions...

3. For close-ups of small, slow moving or static subjects, I like to sight the camera in externally first, then move to the EVF, focus, recompose and shoot. This is fine with a comparatively narrow macro port, but impossible with the big 180 dome. Using 140 dome may help.

[dentrock]

Phil Rudin has posted plenty of WA photos for this lens. Here is a close-up of a 40mm male Nesogobius pulchellus, moderate cropping and minor processing (I tried and failed to upload uncropped version), at 70mm.

 

Not too shabby for a do-everything zoom, so might satisfy fish nerds and perhaps blackwater dudes:

 

 

 

[fruehaufsteher2]

Inside the Sony-ecosystem: Do you think there are advantages over the 28-60 + WWL1b or WACP-C? Just below the surface, not on land - there I personally use the 50-400, WA only from time to time. 

[Architeuthis]

39 minutes ago, fruehaufsteher2 said:

Inside the Sony-ecosystem: Do you think there are advantages over the 28-60 + WWL1b or WACP-C? Just below the surface, not on land - there I personally use the 50-400, WA only from time to time. 

I have both WACP-C/Sony 28-60mm and Zen DP170/Sony 20-70mm. WACP-C for real WA (although I miss the diagonal 180° range, but this is another story). DP170/Sony 20-70mm for the "normal" range, I like it a lot for fish-portraits. There is some overlap at the wide end, but these combinations clearly cover a different range.

 

For our next trip in November (Mafia Island in Tansania, lugagge is even more restricted than usually), I am thinking of leaving either the Zen DP170 or WACP-C, maybe even both of them, at home and just use one (or none) of them. My main WA would be Canon 8-15mm fisheye/Nauticam 140mm (with and w/o TCs)...

 

The Sony 20-70mm will come with me in any case, for over the water use (clearly better than the Sony 28-60mm, but it i larger)...

 

Wolfgang

 

Edited September 13 by Architeuthis

[fruehaufsteher2]

Hi Wolfgang, 

 

thanks a lot, that’s really helpful. 

For the usual dives I am happy with the zoom range of the WACP-C, and if I am looking for the small things, the 90mm is in the pocket. 

 

Just for show: WACP-C is also capable for some sort of macro

[Phil Rudin]

On 9/13/2024 at 5:50 AM, Architeuthis said:

I have both WACP-C/Sony 28-60mm and Zen DP170/Sony 20-70mm. WACP-C for real WA (although I miss the diagonal 180° range, but this is another story). DP170/Sony 20-70mm for the "normal" range, I like it a lot for fish-portraits. There is some overlap at the wide end, but these combinations clearly cover a different range.

 

For our next trip in November (Mafia Island in Tansania, lugagge is even more restricted than usually), I am thinking of leaving either the Zen DP170 or WACP-C, maybe even both of them, at home and just use one (or none) of them. My main WA would be Canon 8-15mm fisheye/Nauticam 140mm (with and w/o TCs)...

 

The Sony 20-70mm will come with me in any case, for over the water use (clearly better than the Sony 28-60mm, but it i larger)...

 

Wolfgang

 

Just for your consideration I am in Bali with the 20-70 and left my 180mm port behind and I am only using the 140mm dome for Laowa 10mm and the 20-70mm, with Marelux I have worked out extensions of 75mm and dome.

 

These were taken yesterday 17 Sept at Secret Bay no crop at 20mm and 70mm to give am idea of what the smaller port will do.

 

 

null

 

 

[dentrock]

I test dived the 20-70 with A7RV, Nauticam housing, 140 dome and a total of 75mm extension (25 adap + 50 ext) as per Phil's rig.

I really, really wanted to say it worked out well... but it didn't.

 

Pros:

1. At approx 5440g exc arms and flashes, rig is approx 450 g lighter on land (cf 180 dome rig in my post above). Doesn't sound much, but I noticed it on my shore dive.

2. Smaller dome makes it easier to line up a small subject before you take the pic.

 

Cons:

1. Noticeably more negative underwater. Some will want to add floatation, whereas I don't think the 180 rig needs that.

2. Max mag down. MFD at 20 still approx 50mm from dome, increasing to approx 100mm at 70.

I estimate the mag at 70 MFD has dropped from 1:2.6 achieved with 180 rig, to around 1:3 - 1:4 with 140 rig.

3. Corner sharpness noticeably worse than with 180 rig; or more precisely, the central circle of acceptable sharpness viewed at 100% does not approach the centre of the long sides of the 3:2 frame (my benchmark).

Even at f8, the 180 rig noticeably outperforms the 140 rig at f16.

This is no doubt because the optical centre of the 140 dome is approx 19mm in front of the lens EP (just a few mm difference with the 180 rig).

4. FOV likely also affected by misalignment, but I won't try to measure this.

 

I could use a shorter extension to improve corner sharpness, but that would drastically affect close focus ability.

 

Verdict: hmmm. OK at 70 if your subjects are not too small (say, 60mm up). OK for shooting larger subjects you come across. Not OK if you are shooting mainly WA.

 

If you want to use the 20-70 a lot, the 180 rig is a better option.

[Phil Rudin]

2 hours ago, dentrock said:

I test dived the 20-70 with A7RV, Nauticam housing, 140 dome and a total of 75mm extension (25 adap + 50 ext) as per Phil's rig.

I really, really wanted to say it worked out well... but it didn't.

 

Pros:

1. At approx 5440g exc arms and flashes, rig is approx 450 g lighter on land (cf 180 dome rig in my post above). Doesn't sound much, but I noticed it on my shore dive.

2. Smaller dome makes it easier to line up a small subject before you take the pic.

 

Cons:

1. Noticeably more negative underwater. Some will want to add floatation, whereas I don't think the 180 rig needs that.

2. Max mag down. MFD at 20 still approx 50mm from dome, increasing to approx 100mm at 70.

I estimate the mag at 70 MFD has dropped from 1:2.6 achieved with 180 rig, to around 1:3 - 1:4 with 140 rig.

3. Corner sharpness noticeably worse than with 180 rig; or more precisely, the central circle of acceptable sharpness viewed at 100% does not approach the centre of the long sides of the 3:2 frame (my benchmark).

Even at f8, the 180 rig noticeably outperforms the 140 rig at f16.

This is no doubt because the optical centre of the 140 dome is approx 19mm in front of the lens EP (just a few mm difference with the 180 rig).

4. FOV likely also affected by misalignment, but I won't try to measure this.

 

I could use a shorter extension to improve corner sharpness, but that would drastically affect close focus ability.

 

Verdict: hmmm. OK at 70 if your subjects are not too small (say, 60mm up). OK for shooting larger subjects you come across. Not OK if you are shooting mainly WA.

 

If you want to use the 20-70 a lot, the 180 rig is a better option.

 

First I made it clear I was using a Marelux housing, port and extensions the extension length would not be the same using a Nauticam housing which has been well documented here.

 

Use one Marelux 1500ml flexbuoy for flotation and also have 5 inch diameter extension rings which add a bit of bounce so not a big issue for me.

 

The bigger point here is that my response was to Architeuthis who did not want to travel with both the 140 and 180 ports and planned on taking only the 140 for 8-15 and not using the 20-70 at all. My response is simply that the 140 can be used for both lenses with good results, if properly used. I am aware that the 180 may give a bit better corners and the 230 is even better. The issue was what do you want to travel with. 

 

You need to go back to the drawing board and work out an extension combination for your own Nauticam housing and port system then retest and see if the results are a bit better.

 

Until then I have attached two more Pipefish at 61mm and Shrimp at 70mm results with the 140 port look good to me.

 

[dentrock]

2 hours ago, Phil Rudin said:

First I made it clear I was using a Marelux housing, port and extensions the extension length would not be the same using a Nauticam housing which has been well documented here.

 

Use one Marelux 1500ml flexbuoy for flotation and also have 5 inch diameter extension rings which add a bit of bounce so not a big issue for me.

 

The bigger point here is that my response was to Architeuthis who did not want to travel with both the 140 and 180 ports and planned on taking only the 140 for 8-15 and not using the 20-70 at all. My response is simply that the 140 can be used for both lenses with good results, if properly used. I am aware that the 180 may give a bit better corners and the 230 is even better. The issue was what do you want to travel with. 

Thanks Phil.

Yes, well aware you are using Marelux.

I also (desparately) wanted to travel with only one dome... mostly because I will also be using the Laowa 10.

 

I don't have your Marelux 140 dome specs, but otherwise the same ext you used (i.e. 75mm total) for Nauticam 140 seems about right in terms of trade-off between corners and MFD.

 

Shorter ext will give better corners but longer tele end MFD and less magnification. I need good photos of gobies down to about 30-40mm length.

 

I agree your pipe fish and shrimp pics look good. As I already mentioned, larger subjects like those (say 60mm and over) are great for the 140 / 20-70 combo, at the tele end.

 

But I wouldn't recommend the 140 / 20-70 combo for other than occasional WA.

 

[dentrock]

A few 'drawing board' tests with the 140 N dome, which only required a dive tub of water...

 

1. Reduce total extension by 20mm (to 55mm comprising 25 adap + 30 ext).

This aligns the EP within a few mm of the dome's optical centre, which should clean up the corners...

 

Result: cannot zoom out the last 10mm or so! (Total zoom extension is about 40mm). Not surprising with a port with only 70mm radius, cf the 180 dome which apparently is 110mm radius.

 

So no good.

 

2. Tried a total extension of 65mm (half way between Phil's 75mm and the above). In this case, misalignment of EP and optical centre is about 10mm.

 

Result: was able to zoom out (just). But minimum focus distances (from the dome) have increased over what I got with 75mm extension, to about 120mm W and 150mm T.

 

More to the point, I made up a 24x36mm focus target and the best I could get at 70mm was 1:4 magnification (cf lens' native mag of 1:2.6). I didn't bother to check the corners at 20mm, although they should be improved over what I got with 75mm extension.

 

If 1:4 is enough for you, this may be a good option.

 

So the range of useable extensions for the 20-70 lens and the N 140 dome seems to be between 65 and 75mm.

 

Regardless, the Nauticam chart recommendation with 180 dome gives much better performance. Sadly, I have read that the widest lens you can use with the 180 is 14mm.

[gremlin]

Does there exist somewhere a good primer to understand what the requirements are for a given lens for adapters? I'm sort of curious to try out the 20-70mm f4 on my a6700 housing, but it's not one of the lens listed in nauticam's port list, and when I queried them I got back something that definitely looked like they were talking about the 16-50mm lens and not the 20-70 because it wasn't a dome at all. I've read the information about the extensions but I think I'm missing the basic back understanding of what to know to make it make sense. Appreciated!

[humu9679]

39 minutes ago, gremlin said:

Does there exist somewhere a good primer to understand what the requirements are for a given lens for adapters? I'm sort of curious to try out the 20-70mm f4 on my a6700 housing, but it's not one of the lens listed in nauticam's port list, and when I queried them I got back something that definitely looked like they were talking about the 16-50mm lens and not the 20-70 because it wasn't a dome at all. I've read the information about the extensions but I think I'm missing the basic back understanding of what to know to make it make sense. Appreciated!

The Sony 20-70mm covers a good range on full frame, but likely not a good fit for APS-c. It would be a 30mm to 105mm equivalent - not wide enough and not close focusing enough to make it worth your while.

[Chris Ross]

3 hours ago, humu9679 said:

The Sony 20-70mm covers a good range on full frame, but likely not a good fit for APS-c. It would be a 30mm to 105mm equivalent - not wide enough and not close focusing enough to make it worth your while.

It's also a big lens which you would have fit from the front of the housing with the N85 port system I would expect, probably need an expensive N85-N120 adapter and N120 dome as well.

[gremlin]

I already have the 90mm macro so I believe that means I have the n85-n120 adapter I certainly have to put the lens in through the front of the unit.

[John E]

Maybe there are smaller diameter lenses that would be better for APS-C.

 

One of the things I like about this lens with Isotta Sony A7RV is convenience since I can use the same extension and 8 inch dome port with the 20-70mm and the Canon 8-15mm plus Kenko 1.4 teleconverter. So this covers the field of view something like 35- 95 degrees then 125-170 on full frame without making any changes to the housing.

 

On Isotta A6600 they have the 102mm port which fits the 20-70mm, Canon 8-15mm and 90mm. They don't have a A6700 housing but I hope they make one.