Good day all

Some advice please. I would like suggestion on what type of lens would be best suited for taking fish IDs. At present I have a Nikon with 10.5, 12-24, 60 and 105 lenses. I need the photos for my research which aims to use selected fish species as indicators of coral reef health. I have a range of fish species and of course some are much easier to take photos of than others. My chosen reef predators such as blue kingfish and bohar snapper swim fast and often don't come in very close. I was thinking that I would have to use a zoom, but the 105 searches so much that I can't see it being useful for fast moving fish. Any help will be much appreciated.

Thanks

60mm and get close?

I have some full-frame shots of Bohar snappers taken with a 60mm, but it took a lot of patience. I have used a small terrestrial 18-70mm zoom on a cropped-sensor Nikon, but the 60mm is better.

Alex Mustard has magnificent images taken with a longer lens.

I would guess that all fish-flashers would say you have to be sneaky and get in close. Rebreathers are thought to take away some of the need for sneakiness, and it's possible that a twin-hose regulator might also help you get closer.

Tim

Depends on your fish I suppose, but I've just spent a week shooting fish (only) as I was running a survey of SMALL fishes in Loch Fyne in Scotland. On full frame I and another full frame user shot with 100mm lenses, but the two using cropped sensor cameras both used 60mm. All yielded useful identifiable fish images. Now we have to sift through about 1000 - very time consuming!

Maybe a Sigma 17-70?

Agree. 17-70mm or the 60mm you already have should be fine.

Alex

I also hunt for reef fish with the 60mm. Very good lens for that. If you feel you need more reach, you could add a x1.4...

That should give you the focal length flexibility. As to the fast action – focus problem; manual focus like in the old “f/8 and be there” days of the Nikonos camera. Learn your camera’s and lens’s depth of field at various focal lengths and f-stops. Make a chart and tape it to your housing or strobe. Anticipate the shot. I spent several hours at a recent workshop with a 15 mm lens fixed at a hyper-focal distance for f/16. Foreground and background were acceptably sharp focus.

Link to hyper-focal:

http://www.outsight.com/hyperfocal.html


No one has comments about the faster (f/2.8) Sigma 18-50 lens. I guess I will have to get the variable f-stop 17-70????

Well, a lot will depend on what you're housing can accommodate. You also have to figure out what you want to do with the lens and whether you are going to be taking natural light photos or using strobes. I rarely use any lens wide open when using strobes. The 17-70 gives you more reach and with my setup, can be used throughout the zoom range with either a done or a wide flat port. Only issue is that the HSM version is too big around for my system so I had to go with the non-HSM one. I haven't had a chance to dive it yet so I'll say no more until after I get a chance to play with it in a few weeks.

quote name='MikeO' date='Oct 17 2008, 12:02 PM' post='188471']
Only issue is that the HSM version is too big around for my system so I had to go with the non-HSM one. I haven't had a chance to dive it yet so I'll say no more until after I get a chance to play with it in a few weeks.
[/quote]

Ooo, I got a nibble! Thanks Mike I look forward to you report. usanexus.com has a notice about the Sigma 18-50. I e-mailed them a question about the se-up in a Nexus housing. NO response. How do those guys justify their existence?



Without access to these lenses and Nexus components, I can only speculate or "rely on the kindness of strangers." From the Sigma, here are the diameter & length for the lenses.



Sigma 18-50 or HSM dia. = 79 mm, len. = 85.3 or 85.8 mm

Sigma 17-70 or HSM dia = 79 mm, len = 82.5



What am I missing about the size difference between the Sigma 17-70 non HSM and the HSM model?


Or -

Click to view attachment[

I'm a great believer in using as appropriate lens as possible. Given that fish don't hang around, zooming might just be another step which might just lose a shot. As an example I've attached an image shot a week ago on a fish survey. I've highlighted the relevant point which the image had to show in order to be useful in the particular survey. Such images do not necessarily need to be at all artistic and selecting a lens which is capable of capturing the detail relevant to the job in hand might be a useful way to go. FYI in this particular case the aim was to look at 'small' fishes of 2~10cm in length and the 100mm Canon macro was ideal on my FF camera.
Click to view attachment

Thanks all for the comments and advice. I very sadly don't have the $$ to buy a new lens so looks like I will be doing the sneaky puffadder trick with my 60mm. And I might also try some shots adding the x1.4. Hopefully lots of patience and persistence will bring some kind of result. If they are any good I will post a few for further comments.