General Wide Angle Lens Question

[jim2386]

Hey guys,

I'm thinking about getting the W-20 lens for my ikelite housing and my Canon A570 setup. I was wondering, does a wide angle lens tend to make you lose Fstops on the high end? This concerns me because I usually shoot in F8.0 to give myself a large DOF so I have the best chance of having everything in focus.

Is this true and what suggestions can you give?

Thanks
Jim

 

[Nemrod]

No, you should not "loose" f stops. Wide angle lenses see a lot of area so there may be more latitude across the scene challenging your little 570IS. My 570 tends to blow out highlights easy which is typical I am told of digital cameras at all levels compared to film.

Wide angle lenses typically have greater depth of field and closer focusing. The Inon 165FE fisheye lens has depth of field from the dome port surface to infinity. With the lens your looking at it will not have that much depth of field but it should focus pretty close comparatively with good depth of field.

The wet mount lenses to these cameras are not like a true wide angle native lens, they are something of a hybrid lens system. I can say that I have not had focus issues with the Inon 105WAL and 165FE. However, they will not fit to the port of the Ikelite housing except for mine, the thread where I made a custom mount and even then there are still issues with minor vignetting. I have both the Ike and Canon housings and use those lenses until my recent mods to the Ike housing with the Canon DC-12.

Personally, I think the Inon 100WAL Type II is a better lens in the 67MM mount that the one you are looking at, but a few more dollars.

My homemade Inon AD bayonet mounted Inon 165 fisheye lens on Ikelite housing with Canon 570IS.

I don't recommend the mod I did unless you already own AD lenses. I am eventually going to pull the port from the housing and cut it .17 inches shorter and reinstall--maybe. Still, I have a FOV exceeding 130 degrees with the 165 and around 65ish degrees with the 105 as is.

This year I am going try under exposing a bit to prevent blowouts by metering for the brighter areas using my Sekonic meter and then boosting the dark areas in Photoshop and also as well I have the RAW hack on one of my 570IS.

N

 

[jim2386]

Nemrod,

Do you have a link to some of your wide/fisheye underwater pictures. I'd love to see them!

-Jim

 

[Nemrod]

I have posted pics here and there. I don't have a log on scary board. Most of my diving these days is dark water unfortunately save for a few times this year.

Mammoth Spring:

A friend hovers, this one shows flare in one corner from poor framing on my part:

Ginny I think:

Devils Eye;

Snell's Ring:

Headed to Bahamas in a few weeks, hopefully a few good shots will result. The pic where my friend hovers, it looks as if he is some distance away, actually, I could have reached out and touched him, that lens sees a full 165 degree field of view.

N

 

[np251]

The way wide-angle lenses (and fish eye lenses) with a dome port work is that the actual scene you see is presented as a virtual image on the the surface of the dome (due to the air-glass-water interface), and exist as a focal plane about a foot (or so- depends on the curve of the dome and the angle of the lens) away- it effectively becomes one large 2-dimensional 'page' that the camera focuses on. This has the result that large aps like 2.0/2.6 etc have 'unlimited' depth of field where everything in view is in focus. This is great because it lets you open up the ap for quick shutter times and still gives sharp focus throughout the dof.

This lets you focus on something literally touching the dome port, while still having background in focus- a technique called close-focus wide angle demonstrates this great

i have some pics using the A570is with the inon UFL-165 that Nemrod mentioned above.*

*i would if i could get them to upload. pm me if you want some emailed

 

[Nemrod]

I would really like to see them. If you would want I could put them up via photobucket.com if you like.

N

 

[np251]

Picasa Web Albums - neil - monastery 2-21

thats some of the better ones from this weekend.

Picasa Web Albums - neil - cypress sea t...

and a few from a boat trip a couple years ago.

Picasa Web Albums - neil - monterey brea...

and a few more, sans strobe


i have a few more, but these are the only really accessible ones while im at work

 

[np251]

got the embedding to work- here are a few keepers...

 

[Nemrod]

I really like the starfish. Which lens are you using for those and how far away were you from the starfish? Were is the kelp forest shots? Thanks.

N

 

[np251]

These are all shot around Monterey and Carmel area. The starfish was off a diveboat sitting about 1/2 mile off the shore from Pebble beach, where they do the PGA golf tour. I used the UFL-165, and he was maybe 4 inches from the front of the dome. Was very surgy that dive so i didnt want to get too close in case i damaged him or the lens.

The anemone in #3 was taken on saturday. One of my favourites. His closest arm was maybe 2 inches from the dome.I think the orange spnoge in #2 might have been within about an inch.

All of those were with the UFL-165 and all but one were strobe lit (YS-27dx- lovely little manual strobe).

Love that last one of yours, very voyeur-esque.