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Patterns

Member Since 02 Nov 2002
Offline Last Active Apr 09 2009 08:27 AM
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Posts I've Made

In Topic: Any experience with Inon lens system?

05 June 2007 - 09:28 AM

Personally (and it would be different perhaps for other people) if I'm thinking about underwater cameras my priorities (that come to mind now) are:

Must have:
- Manual exposure
- custom white balance
- Available Inon adapter for AD or AD28 mount
- reasonable low-light focus capability

Really nice to have:
- wide zoom lens
- raw
- option to set the flash manually to very low power (since I use manual control for my flashes)
- ability to store a couple of settings (for wide-angle, macro, whatever)
- all controls by pushbuttons rather than dials
- low noise sensor
- long battery life (enough for 3 dives)
- smaller housing, but with a bit of spare space for a silica gel pack
- easy to feel the shutter half-press position with the housing

Others
- longer zoom
- better screen
- screen visible from a high angle while in the housing

I'm sure I have left out lots ...

-David

In Topic: Any experience with Inon lens system?

03 June 2007 - 09:35 PM

I don't dive much these days, but I have been thinking about buying the A570 and housing to replace my S70 (because of poor focus) and C5050 (because it uses M67 mount - see below) kits. I already have both AD-mount and M67 (threaded) wet lenses. My overvations:

(1) If you want to use wet lenses, the bayonet mount is far easier to use. That's a big tick in favour of your proposed system.

Problems with threaded mount (as opposed to the bayonet):
- it's hard to align and screw in the lenses underwater, especially the wide-angle. You'll may be in a hurry but you still need to do this carefully to avoid dropping or damaging anything.
- it takes much longer to complete this process with the threaded mount.
- when you unscrew the lens you have the problem of not knowing exactly when the lens will come free, which increases the chance of dropping something.
- eventually you will cross-thread the lens and housing. On my Oly C5050 systems it's the housings which eventually lose the thread. The wet lenses start to jam on the housing after a while, adn a number of times I have put a lens on gently (I thought) and have needed the tool kit to get it off again. And I think I'm not unusually weak. For this reason I have decided in principle that I will never buy a threaded mount again for underwater use. (This actually eliminates a couple of cameras which might otherwise be interesting, but low-hassle operation is important to me underwater.)

I love the way with the bayonet mount that it guides itself into place, and then a quarter-turn produces a very obvious click into position.

(2) I don't have the latest Inon flashes but I have 3 older ones in the same series and have found them completely reliable. (As opposed to my frustrating experiences with two other brands.) On irritation with one of them (I don't have it with me at the moment, but I think it's an older D2000) is that the power selection for manual power can rotate 360 degrees This makes it extremely difficult to work by touch at night. For night use, it's good to be able to find the end of the adjustment range by turning to one end of the range, and then count clicks back again. On the other hand, in daytime that's not needed.

(3) Inon also sell a AD-mount lens caddy which attaches to your flash arm (or elsewhere with a bit of ingenuity) and allows you to safely and very quickly attach the lens to the kit when it's not in use. Well worth considering. A two-sided version lets me park both the wide-angle and the macro converter at once.

(4) I'm not sure that IS will work as well underwater. As I understand it (I'm certainly not an expert on this) the IS calculates how much the image will move (in terms of angle) when the camera wobbles, and compensate for that. But I suspect that underwater, a 1-degree movement of the camera will have a different effect on the apparent postion of the subject, compared to the same movement of the camera in air (because of refraction at the air/water interface). Hence the IS may compensate incorrectly for the camera movement. Using wet-lenses will also have an effect. I don't know whether you can tell the IS system that you are using adapter lenses, and choose a setting which will work appropriately underwater with whatever external lenses you may or may not be using.

Maybe someone who knows the math can work out that being underwater is equivalent to using say a 0.75x wide-angle converter on land, or something like that. (I don't know - I just made up the number as an example.) In any case I suspect that the centre of the image and the edges react differently to a given level of camera movement.

Having said all of that, I am pretty sure that IS will still improve the results when underwater, but I suspect maybe not by as much as usual.

(5) No raw capture on the A570 until someone manages to hack the DIGIC III firmware ...

(6) I think (haven't checked back on the A570) your proposed kit would all use AA-batteries. Using a single battery type is a significant advantage for me, but some others don't seem so fussed about this.

Hope that's useful (sorry I don't have time to check references, shouldn't even be writing here now but I was thinking about similar kit too and am organising my thoughts...)

-David

In Topic: Canon Powershoot Hack..the way to raw format and more!

27 May 2007 - 09:25 AM

- However my impression is that battery life with the hack running is really dreadful. That may turn out to be because I'm not using the camera much and the NiMH batteries may be discharging before I actually get around to using the camera. I'm hoping to test that in the next couple of weeks, but it's hard to find the time.

I'm not going to have time to do a proper test in the foreseeable future; there's too much else to do.
However, I loaded up with a new pair of batteries (Enneloops, as it happens; rated 2000mAH) this morning. After 50 quick shots and some review and deletions, when I started the camera again 5 minutes later the battery meter read 94% [Edit: 94% in playback mode; 74% in record mode. The meter is very sensitive to the load on the battery]. Of course this number while precise is not accurate, since I haven't calibrated the 100% and 0% points for any particular kind of battery. Still, it suggests battery life is not as bad as I previously thought it might be.

Most of my other battery sets are rather old, and I have decided to replace them before the next big trip.

-David

In Topic: Canon Powershoot Hack..the way to raw format and more!

26 May 2007 - 07:14 AM

This sounds fantastic! I wonder if somone is on the way to crack DIGICIII out there?
/O


Last time I checked (2 weeks ago) I couldn't find any indication anywhere that someone has succeeded yet with the DIGIC III chip. Others (especially if they speak Russian) may have more luck.

However, this would take the Cannon 710IS to a quite favourable position as a good UW-compact as compared with for instance G7 as there would now be RAW support.

/O


I have tested the hack on my A710IS. Nothing scientific, but:
- The hack is loaded from a file on the SD card at bootup. It can be enabled and disabled by locking and unlocking (respectively) the write protection on the SD card before turing the camera on. The hack loads at startup, and remains running until the camera is turned off. There is no change to the camera's firmware. Note: locking the SD card does not prevent the camera from writing image files.
- It seems (from my reading elsewhere) that the raw file is 10-bit not 12-bit. This is consistent with my observation that it's quite hard to do better with the converted raw file than the camera does itself in producing its jpg.
- It is possible in Adobe Camera Raw to rescue some minor overexposure. I think this would be useful for underwater, where I find it really hard to avoid occasional overexposure when one part of the scene turns out to be more reflective than I realised.
- However my impression is that battery life with the hack running is really dreadful. That may turn out to be because I'm not using the camera much and the NiMH batteries may be discharging before I actually get around to using the camera. I'm hoping to test that in the next couple of weeks, but it's hard to find the time.
- The additional capabilities include:
-- real time RGB histogram
-- raw
-- better exposure bracketing
-- control of display of all on-screen information elements

I decided not to get the housing for the camera as it seems that Inon does not make an AD-mount adapter for it.

-David