It looks like Storker is again trolling for a lively debate. Since I am one of those who has been espousing the use of manual mode, I guess I will take the bait!
First off, I don't think anyone here has said you must shoot manual. If you are happy with your photos the way they are, go ahead, keep shooting in auto mode.
Rule #1 for me (and many others have also pointed this out) is that one should not take a camera underwater until they are very comfortable with their buoyancy and situational awareness underwater. I would say this would take on the order of about 200 dives or so for most people. Once you are very comfortable underwater, and you are getting perhaps a little bored just looking at stuff, then maybe you can start thinking about taking a camera underwater. There is really nothing worse on a dive than observing somebody with 30 dives or so flailing around out of control trying to take pictures underwater.
If you want to start off in automatic mode, go right ahead. If you are happy with your photos, that's great. On the other hand, if you are the kind of person who wants to improve their underwater photography (and I would think this would include many people who are perhaps motivated enough to read this forum), then a very good tip is to try manual mode. As I said in another thread, there are several good reasons for that. Most importantly is that automatic modes are designed to work well topside. Taking pictures underwater is different. Underwater, you will probably want to minimize ambient light, and rely more on your strobe to bring out the colours. Automatic modes want to do the opposite; rely on the ambient light and add flash if necessary. Also your camera does not know it is underwater, and has no way to compensate for the fact that the light fall off from your strobe with distance is much greater underwater than topside. The easiest way to take control of your settings is to simply flip the switch to manual. It's easy!
Shooting manual:
- Decide on shutter speed or aperture, depending on subject type and priorities
- Evaluate overall image. Is it zone 3, 4, 5, 6 or 7?
- Adjust exposure according to meter. Optionally, dial in exposure bias according to overall zone
- Shoot
Shooting auto:
- Decide on shutter speed or aperture, depending on subject type and priorities, set auto mode (P, S, A, or "M" with auto-ISO)
- Evaluate overall image. Is it zone 3, 4, 5, 6 or 7?. Optionally, dial in exposure bias according to overall zone
- Shoot
I am a little confused by this. Why bother metering the scene? Are you afraid of wasting film? Welcome to the digital age! There is no such thing as wasting film anymore. There is also a lot less fiddling with settings than you are implying. Most photographers with some experience have their favourite base settings for wide angle, and their favourite base settings for macro. When I have my macro lens on, I am pre-set to ISO 200, f/16, shutter 1/200, and strobes at half power before I even get in the water. If I want to, I could do the whole dive on those settings. Typically I might only adjust aperture, and perhaps only a few times during an entire dive. If I have to back off for a larger subject, I might open up to f/12. If I have to get close to a very small subject, I might stop down to f/20. Alternatively, I could leave my aperture at a medium setting and adjust strobe power a little as necessary. This is what I did when I was shooting with a compact camera. For wide angle I will bump up my ISO to 400 and open up my shutter a little more. And that's about it.
Since I am shooting digital and not film, I can check my exposure immediately after every shot and it is bang on 95% of the time. If the exposure is not very close to where it should be, it is because perhaps a piece of kelp is blocking a strobe, or maybe one strobe was accidently switched off (which is an occasional nuisance with the YS-01s). But at least I can recognize the problem right away and correct it.
If you are shooting in automatic or a semi-automatic mode, and the exposure is wrong, then it becomes a lot more difficult to diagnose the problem.
Storker is also lumping in all the semi-automatic modes (P, S, "M" with auto-ISO) with automatic which is also confusing. Go ahead and shoot in a semi-automatic mode if you want. If it works for you that is great. Probably you are already used to it from the film era. In my humble opinion, these modes (which basically allow you to control some settings but rely on the camera's meter to get the final exposure right) are relics of the film era when one did not want to waste film. Now that we are well out of the bronze age and into the digital age, you can check you exposure immediately and much more reliably by simply glancing at your LCD screen. Would you not trust your own eye more than the camera's meter?
For these reasons, I think most newer photographers who are seeking to improve their underwater photography will have an easier time just shooting in manual mode rather than in a semi-automatic or automatic mode. But again, this is just my opinion. Nobody is telling anybody what to do here. Except for perhaps Storker ("DON'T shoot in manual").
cheers and happy diving!