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 Friday at 09:53 AM 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