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Member Since 18 Jul 2005
Offline Last Active Jan 22 2011 04:30 PM

Posts I've Made

In Topic: Image sharpness problems

28 December 2009 - 12:20 PM

Hello All,

Thank-you all for the great advice, observations and insight (both with postings and email)!

Several of you have questioned whether I have the proper extension ring in my setup, and it appears that I may not! Let me explain. I decided to double check that I was using the correct extension ring, and I naturally went to the Aquitaca website. I looked up the correct ring for the Sigma 17-70mm HSM, on a D300, with an 8" dome port, and it calls for part number 18462 (39.5mm extension). I've been using part number 18453 (28.5mm extension). [sounds of me screaming...]. So I went back to my file, where I kept a hardcopy of all the Aquatica information from when I ordered my kit. Guess what? At that time they didn't list the "HSM" version. They listed only the "Sigma 17-70mm F2.8-4.5 DC Macro" which called for the part number I purchased. I remember talking to Aquatica about the lens and they stated their best guess was the same extension. They were correct, but they've changed their recommendation on the proper extension. Today, they list the 39.5mm extension (#18462) for both versions of the lens.

Conclusion: Aquatica, after further testing, has changed their recommendation for the proper extension ring, from a 28.5mm to a 39.5mm. They recommend the same thing for both lens.

Lesson: When things are not perfect, check Wetpixel, and talk to the the housing manufacturer, because recommendations DO CHANGE!

I assume that while this isn't common, but it does happen that recommendations change because more extensive testing reveals that a different port extension works better. Have others had this happen to them?

I have not tried the check 'davephdv' recommended yet, but I do want to compare what I've been using against the proper extension ring, as soon as I get that. Several of you stated that I need to check and double check that I had the correct port extension. Since I had what was recommended I moved on to the next thing in the list, when all along I should have gone back and double checked that the recommendation hadn't changed.

I don't know how to thank-you all enough. I would never have figured this out without all the great advice. It is clear to me from the number of you talking about the port extension length that this is a problem that has come up for many of you, and which is not an easy one to explain. And I shouldn't trust just one source, but instead do some experimentation of my own!

These day's I'm back in school, and barely working part time, so I don't get to purchase items much, and I don't get out to dive very often. However, I will get this tested in the next few months, and post an update.

Thank-you all!

In Topic: Image sharpness problems

18 December 2009 - 02:02 PM

Thank-you All!

I haven't shot any other lens in the 8" dome port, but I have some pictures with a 60mm in my macro port. I can put a couple of the 'sharpest' ones up for comparison. And I've looked through my pics and selected a couple more with the 17-70mm Sigma (same dive trip) that are as good as I've managed to get.

I compare the best I've managed to shoot, with what I see posted here regularly and I always feel like I'm doing something terribly wrong, or I have something messed up with my gear. Composition isn't my thing, but take a few thousand pictures underwater, try everything, and a few should come out quite sharp.

First two shots are with 17-70mm on a trip to Port Hardy, Canada (north end of Vancouver island). These are about as sharp as that lens (with me shooting it) gets underwater.

Giant Pacific Octopus - 17-70mm

Sea cucumber - 17-70mm

The next 5 shots are all with my 60mm in my macro port. They are sharper, and they just tend to be easier to shoot (much higher success rate for 'clear and sharp' pictures).

Rock Scallop - 60mm

Leg of Puget Sound King Crab - 60mm

Spiny Crab (I think) - 60mm

Grunt sculpin - 60mm

Anenome - 60mm

So would it be expected that the 60mm is going to be a lot sharper, in general?

I have a 10-17 tokina FE I can shoot in the dome port (never have yet), which might show if the port is a problem, but the lens is so different I don't know if it would offer any real information. The lens seems to be quite sharp above water, so I was thinking that it isn't likely to be the camera or lens, but how I was using it underwater. I'm just not sure.

Oh, when running through pics from that trip I saw I had a couple of a crew shooting digital, 3D (two cameras in one housing), IMAX video. What a cool camera, and a nice bunch of guys doing the filming. I can't wait to see the movie they are filming (in a year or two?).

Digital, 3D, IMAX video camera in action - 17-70mm

Thanks for any insight!

In Topic: Image sharpness problems

18 December 2009 - 12:42 AM

I have the same lens on my D300 using an Ikelite setup with the 8" dome. I just shot some photos in the Philippines with the lens and can share a couple of examples:

Macro 70mm

Wide Angle 17mm

I have seen some examples of poor edge sharpness at 17mm with this setup, but it's not extreme and improves at > 17mm. You can see some of this in the Wide Angle shot linked above. At 70mm it's looking pretty sharp.

Of the photos you posted the shimp in the anemone looks pretty fuzzy. The meta data says f32, which might be too high? The others in the first set look pretty good to me.

Could you provide some details of what focus mode you are using? There are many options on the D300 and some may not give the expected results if you don't use them in the expected manner. AF-S, Focus priority, and Single point will give the most consistent and simple results.

Hi Dave,

I took dozens of photos of that, and other shrimp over the course of a couple of dives, and I was never able to get a single one that is truely sharp (in focus?). I shot a wide variety of f-stops, and several speeds, in addition to both ISO 200 and 400. Most of the pictures I took were in good light, and at less than 40 feet. All were with two DS125s. I thought this picture was a good example, because even at F32 I didn't really have anything in the picture that was really sharp.

I shoot in both AF-S and AF-C mode, but set it to focus priority in either case. I've shot with single point focus, but unless I'm shooting non-moving subjects with 'good light' I find I have problems getting a focus lock. So I often shoot in 9 or 21 point dynamic-area AF.

I've actually dove with a friend who carries a tiny sony P&S without a strobe, and we've both shot pictures of nudibranches. He seems to get a much sharper image most of the time. Or rather, everything will be in focus.

I've even tried manual focus, while lying on the sand, looking through my viewfinder and taking multiple pictures. That, I've discovered, just isn't a solution for me.

It just seems like the details are not really all that sharp (in focus).

Here is a picture I took with the same setup, at F10, where I was able to get the eye truly in focus:

Eye in focus

That seems to be very 'rare' though.