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I have just started shooting underwater macro and despite having enough light power to light a small city and shooting at 1/50 & f22 generally I am finding that too many of my shots have a DOF that is just too small.
I have been using a 60mm Nikkor macro.

Will a 105 give my a better DOF

Dof is impacted by ...

1. Aperture (larger aperture, shorter DoF)
2. Distance from subject (the closer you are, the shorter the DoF)
3. Focal length (a wide angle lens has a much greater DoF than a telephoto lens)

So I am guessing that even though the 105 would enable a greater distance from the subject, it would not give a better DoF.

Can anybody assist - I started off confident, but now, not so much. Tired. Long day.

does the 60 have the same fstop range as the 105??

If so, then theoretically (and speaking with as much confidence as Greg) then yes, the 105 should be shallower

The 105 has better DOF than the 60mm.

Both are 2.8 lenses.

Birdy, can you explain in simple speak why the 105 has better DOF.??

I meant the minimum apeture (at f=inf)
one thing you will notice is that as you focus on closer objects the apeture decreases (fstop increases)

On the 105 it is f/36

when focusing close I usually use f/32 (when focused close I thing it can go to f/55)

The way I see it, if you need to be further away from the subject to achieve the same crop or composition, then all else being equal, you should get greater DOF.

I think we need a test at the next minimeet

As previously posters mentioned, the 105mm can go up to f36 or further and distance can be far than the 60mm and it can achieve a great DOF if you close to the object, though the 60mm has to be closer the object, DOF is greater than the 105, if we have the same distance on both lenses, I can see most of them are same DOF
One of our members pluckaduck has a diving housing with the D70 and he experienced with DOF on the short focal lenght.
I have tried both lenses and found the 105 has better DOF than the 60, if member can, we can do a test on the next mini meet, I have both lenses in hand same as the Tamron 90 and 180 or Nikkor 200/f4.

I would be very interested to see or hear the results of any tests. Basically I am looking to compose the same shot but have a slightly greater distance with the 105. A typical underwater macro subject is 5-10mm long so the lens-subject distance is VERY small(ie 50-125mm).

Underwater you need to keep as little as possible water between the lens and the subject to minimise back scatter but DOF is a real problem.

This is what I love about this forum. Someone has a question and they don't just get palmed off , people really try to help. I too would love to see the results of a comparison DOF with the two lens.

Oneputt wrote:This is what I love about this forum. Someone has a question and they don't just get palmed off , people really try to help. I too would love to see the results of a comparison DOF with the two lens.

I'm able to do it next week-end at the mini meet, I have two those lenses, anyone want to play, welcome.

In theory, the longer the focal length then the less DOF...but conversly...the closer you get to your subject then the less DOF. A 105mm lens would lose DOF because of its focal length, but would gain DOF because tou are further away from your subject. I'm guessing that the DOF would be very simmilar if you frame the image the same way each time.

If you are shooting underwater, would the slower speed of light have any undue effects; in particular regarding the incident light, the reflective light and the input light (sb800). In addition would this impact on the DOF

Cheers,
Terry

Terry's the first one to attempt to address the issue of the fact that Steve is talking about shooting underwater. That opens up a whole different can of worms.

First of all, I've never shot underwater, but we did cover many of the issues in one of the photography courses I did ... oh, about 30 years back.

Probably one of the biggest factors in shooting underwater is the light fall-off factor. Move down below a few feet from the surface, and the light begins to fall off dramatically. Hence you typically need to bring your own light sources with you. Note that waterproof housings for serious cameras generally carry connections to waterproof flash housings. Now you understand why.

And of course the refractive qualities of light, when transmitted through water, are changed as well, and it's not too different from the effect of the crop factor that wee with our digital cameras.

To that end, you might want to look at the sort of lenses that are available for the Nikonos cameras, and observe that they're all at the wider end of the focal length spectrum. Bearing in mind that those are for a full frame 35mm crop, you may want to widen your scope by the digital's crop factor of 1.5 and use that as a starting point for shooting underwater images.

Bottom line is that a 60mm is probably at the outer end of the focal length spectrum that you'd be wanting to shoot underwater with, and you might want to look at something in the 18 - 24 mm range.

I have a 12-24 and 10.5 fisheye that I am using for wide angle and BIG close focus work but for the little wierd critters you really need to get in close hence the requirement for a good macro lens.

I used to use a 150 macro on an old FG that I had and it worked pretty well. It is prety common for film shooters to use the 105,150 or 180 so I expect that the 105 won't be too long.

My real concern is that if the DOF on the 105 is even shallower than the 60mm then it is probably not worth spending the money on the lens and port to go on my housing.

Following are a few examples or what I am experiencing. All of these were shot at f20 or f22.


Goby: The guys head is onlt about 7-8mm across


Barnacles: Each shell is 5-6mm long


Decorator Hermit Crab:


Disc Coral: About 20mm diameter

Love that pic of the hermit!!! What case do you use?

P.s. top pic looks like a blenny.

Unless you are shooting in the first 5 meters, strobes (underwater flashes) are essential. You can get as much light as you want with these strobes....so is light really a factor?

Bugger.
Made a serious error in previous post..
DOF will be the same if the aperture & magnification stays the same.
Eg. at 1:1 at F16 60mm & 105mm will have the same DOF.

Cheers. PS. You might also find this discussion informative.

Answers to the previous posts.
I have an Ikelite housing with a pair of DS-125 strobes. Plenty of light power In fact I think that a number of my subjects have been well fryed by the time I am finished with them.

The Wetpixel forum is good. I think that the most salient point made was that the 105 gives more compositional space. I have found it quite difficult on occasions to get in there with the 60 because there simply isn't any space around the subject to put the strobes.

I think that I have gotten to the stage of buying the 105 and it will just be a matter of deciding when there is suitable 'little' stuff to warrant committing a dive to it.

Still very interested to see if there is a real difference in DOF betwen the 2 lenses though

Steve,

Found this link you might find helpful.
As for finding little stuff to photograph, have you found any nudibranchs in your area?
They were my all time favourite creature in my diving days...
Used Nikonos II & Nikonos III with extension tubes back then.

Cheers.

Arek,
thanks for that link. Not quite sure what way to jump now

I have a few nudibranch shots but not many that areworth sharing. I quite like the following one which I snapped in about 3m viz at Byron BAy a couple of months ago



Steve