9 replies to this topic

[ordvr]

Hello All,

I've had my D300 about a year now, and I've primarily used my Sigma 17-70mm HSM underwater. I shoot it in an Aquatica housing, with the 8inch dome port, and dual DS125s, all in manual mode. The problem is that I simply cannot get a 'sharp' image. Above water the images are quite sharp, so I'm not sure what the problem is. Regardless of whether I shoot at the wide end or macro, I have a terrible time getting a sharp image. I've put three images (not cropped, just resized significantly and converted to JPG) at:

Sample pics showing sharpness problems

I'm not sure what the problem is. I shoot in manual mode, and generally shoot at f/16 or smaller apertures, 1/100 to 1/200 second. I've had about 75 dives with this camera, most with this lens and I'm just not happy with the results. I actually was able to take better pictures (crisper/sharper) with my old camera (also shot in manual mode).

I have some that are okay, but this next gallery (large pictures, not significantly resized) are the best of a couple thousand shot on a trip.

Socorro trip

So, does anyone know if this is typical of this lens? Do I need a diopter? Could it be a camera problem? Am I just in need of some serious instruction?

I really appreciate any insight anyone can give. I'm pretty frustrated.

Thank-you!
Greg Cooley

[davehicks]

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.

[ordvr]

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.

Thanks,
Greg

[Alex_Mustard]

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.

Thanks,
Greg

There definitely seems to be something weird going on at the top of that frame - above the eye. I guess it is possible that a lens element might have become misaligned. Although this would also effect it out of the water.

I always used my 17-70mm (non-HSM) with a dioptre and was pleased with the results, but many here use the lens without a dioptre and are equally happy.

Here are a few shots - all at very close camera to subject distances, so there is not a lot of depth of field, but all acceptably sharp to me:

At 17mm (8" dome and +3 dioptre)


At 19mm (4" dome and Canon 500D dioptre)


At 19mm (4" dome and +3 dioptre)


I no longer use the Canon 500D with this lens as it gave inferior corner sharpness than the single element dioptres.

My gut feeling is that your lens might be mis-aligned after seeing the stingray picture. Alternatively if you are up at F32 you may be getting some softening across the whole frame from diffraction?

Alex

[davelew]

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.

The bokeh on the top left of that stingray image strikes me as unusual-- it reminds me of the out-of-focus swirls sometimes used to disguise license plates and faces.

If you don't get that effect shooting on land, I wonder if there could be some misalignment between the camera and the dome port that is curving the focal plane?

[ordvr]

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!
Greg

[jkane]

The first thing I would suspect is whether the dome is in the correct position relative to the lens; specifically the lens' nodal point. This is crucial for domes, but not so for flat ports. If the relative position is wrong, it's difficult to impossible to get sharp images. The relative position of dome vs lens is adjustable with dome extensions. I'm not familiar with Aquatica, but most housing manufacturers supply guidance on the correct combination of housing, camera, lens, dome, and the dome extension if one is needed. If info is unavailable, you can always experiment with various extensions to find the optimum one. Evidently a diopter is not necessary, but it may be worthwhile to confirm this for your specific equipment. Good luck.

[davephdv]

My thought is that either you need a diopter or you have the wrong length extension ring.

A rough and dirty way to see if you have the proper length extension ring is as follows;

With the lens in the camera, zoom out to it's widest focal length and open up the lens all the way. Looking at the lens from the front you should see your reflection in the aperture of the lens. If the lens/dome is properly set up your reflection should stay in the center of the lenses aperture even as you move your head around the housing. This means you have the proper set up of lens and dome. If your reflection moves out of position or away from the center of the lenses aperture then your setup is suboptimal and will affect the sharpness of your images.

Photographers often make the mistake of using too short an extension ring. You can focus closer if you do this, but you lose sharpness.

[ordvr]

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!
Greg

[Bigeye Bubblefish]

I also have this lens (non-HSM) with a D90, Aquatica housing and behind a 8" dome.
I bought it 155£ on Ebay.

As per Jean (VizArt) recommendation, I am using at 39.5 mm ring.

The lens was OK at 17mm, but not very sharp.
I have the same distortion @ 70mm. This is probably due to the dôme, or maybe an invisible scratch inside the dome.

I prefer the sharpness of my Tokina 10-17 @ 10 and 17mm

Tokina @ 10mm

Sigma @ 17mm

Sigma @ 70mm

Damien

Edited by Bigeye Bubblefish, 30 December 2009 - 12:25 PM.