I must admit Macro photography is not exactly my favourite genre both underwater and topside however I do enjoy a bit of critter hunting.
I was sure that the A1 would be an absolute beast for topside wildlife and underwater wide angle, however I did not feel comfortable at all with the performance of the Sony 90mm Macro lens.
It has a reputation for hunting and a lot of focus breathing that make it hard to use for topside focus stacking.
I have been playing with the lens topside and I did see examples of both so I was somewhat skeptical taking it underwater.
I was perhaps over worried so I set up the camera for the worst case scenarios:
- Focus limiter set to 0.3 – 0.5 meter
- CAF priority set to Focus
- Aperture drive – Focus priority
I went in with autofocus set to tracking flexible spot.
Port and Focus Gear
I have always mixed feelings for focus gears and mostly I use it to make sure I am hitting the minimum working distance and therefore maximu magnification.
The focus gear for this lens is a large item and does not allow to operate the focus clutch. The operation is quite easy as the focus ring does not have an excessive long run.
I already own the 45 Flat Port that I use for the Sony 28-60mm and also have the 35.5 N120 to N120 port adapter so I thought how do I make this 105mm long?
Nauticam makes convenient adaptor rings of various length to go from N120 to N100 port size. I got the 25mm that resulted in a saving of £441-260=£181 which I used to buy another part.
The rig as assembled looks like this. In effect even the 110 port starts wider and gets narrower.
Before going to the pool I realised the housing does not have an M10 mounting point but you can adapt one of the points that go to the bars connecting the angle. Will be done at some point. So I went in without focus light in a very very very dark pool.
As I packed my props I realised I did not really have any good macro target however a friend came to the rescue. An instructor of a diving center that uses the same pool brought a small leopard and octopus that sank and were perfect targets.
As you probably know I am obsessed by obtaining the absolute maximum performance from each lens. And this for a macro lens means shooting at the best aperture, for this lens f/4-5.6 and stacking. However this is not available underwater. You need to pull your shot from a single image and this means the lens won’t be at the best performance.
I started at f/11 which gives a respectable MTF50 and to be honest I am impressed!
I then pushed the lens to f/16 I could see resolution dropping as depth of field was going up.
In order to get depth of field of an overall scene with the octopus I had to go all the way to f/22 diffraction zone.
Yes with the high resolution of the sensor those images are still ok or at least so they seem to me.
I think this lens wide open makes an amazing bokeh that will probably be still there at f/4 so something to check.
Field Impression and Ergonomics
First of all I did not regret setting the lens to close range using the focus limiter. This will give you a frame 19 cm wide if you feel that is too small and you are just trying to get some fish portraits perhaps leaving this to full is a better idea. Likewise if your targets are bigger.
I did not get any hunting despite the dark conditions and I am not sure if this was due to this setting or if this helped.
CAF worked in all situations the A1 can practically see in the dark however in order to get focs tracking and eye detection working (it detected the eye of the leopard) I needed to switch on the focus light of the strobes.
I believe tracking and detection requires a level of scene brightness higher as the camera is effectively in video mode. When you half press the aperture drive meant it would focus thought it had not tracked anything. I got 2 shots not focussed on the subject because I moved.
The focus gear I believe is not required unless you want to do super macro or to make sure you are as close as you can get but I do not regret having it as the run is pretty short with the focus limiter is on.
Alex Mustard tried the 90mm with the A1 for blackwater and said it was better than the Nikon D850 with the 60mm which is a well known blackwater combination. My tests confirm this combination is very very powerful even in the dark and with a little bit of light it will focus on anything. If the lens goes back and forth is because you are close or over 1:1 reproduction ratio.
Overall my concerns apperad not justified and this combination is a solid performer. Probably next steps are getting an SMC magnifier to push this even further.
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