100mm macro in superwide dome port?

[michaelsweet 0]

is it possible to shoot a 100mm macro lens in a fisheye dome port - i'm using the 1dsmk11 in the seacam housing - i'll be traveling soon and i'd love to take just one port - 90% of my pic's will be wide angle - what about a regualr dome port? any help is appreciated as i know i won't be able to get a new flat port before i travel

many thanks

michael

[t-bohn 0]

Hi Michael,

 

I have no experience with your Seacam dome but my main concern would be to get it scratched when going macro with it.

When I'm shooting near the ground, my housing is sitting in the sand from time to time.

My dome port (Subal) is on the same level and I would be very worried to scratch it if I would use it this way.

 

Cheers

Torben

[Paul Kay 65]

Yes, it is perfectly possible to use a 100mm macro lens behind a dome port. If you are using the 100mm usm lens from Canon its simply a matter of ensuring that it fits - so you will need to see if and which extension tube you need. I tried out the 100mm usm macro behind Seacam's DP95 and PVL35 Extension tube recently in Tahiti. On the dive I found that I could shoot small clown fish (now called 'Nemos' I'm told!) with no problem and the results are certainly sharp enough. You still need to adjust for a slight amount of chromatic fringes during the raw conversion, but differently to the adjustments needed for a flat port. You will need to shoot at f/11 or f/16 so any non-flatness of the image will not be noticable. My only concern is the one already mentioned - it would be very easy for the Superdome to physically contact the subject, so there is a risk that you could damage either dome or subject.

[StephenFrink 9]

Yes, it is perfectly possible to use a 100mm macro lens behind a dome port. If you are using the 100mm usm lens from Canon its simply a matter of ensuring that it fits - so you will need to see if and which extension tube you need. I tried out the 100mm usm macro behind Seacam's DP95 and PVL35 Extension tube recently in Tahiti. On the dive I found that I could shoot small clown fish (now called 'Nemos' I'm told!) with no problem and the results are certainly sharp enough. You still need to adjust for a slight amount of chromatic fringes during the raw conversion, but differently to the adjustments needed for a flat port. You will need to shoot at f/11 or f/16 so any non-flatness of the image will not be noticable. My only concern is the one already mentioned - it would be very easy for the Superdome to physically contact the subject, so there is a risk that you could damage either dome or subject.

<{POST_SNAPBACK}>

 

 

If Paul says he has had good luck using the 100mm macro behind a dome port, I believe him. But, there is a wild card. He used it behind a DP95, and you want to use it behind a fisheye port. The issue is that the minimum focus of the 100mm macro is 12 inches. IF the dome has sufficient diameter to allow the vitual image to appear 12 inches or FARTHER, it will focus. If the dome creates a virtual image NEARER than 12 inches, the lens won't focus at all (unless you add a diopter).

 

So, even though the 100mm macro focuses to 1:1, it does so at a dstance too great for the use of some dome ports. Yes, you would be able to use the superdome (9" diameter ... approx. 18" virtual image) with the proper port extension, although why would you? Maybe the DP95 uses a similar curvature dome, although in a smaller package. That one I can't answer without further research. But, I can guarantee that if you try using a 100mm Canon macro or a 105mm Micro-Nikkor behind a 5" dome (approx. 10" for the virtual image), you won't be able to achieve focus without an accessory close-up lens.

 

BTW, I have done a pool test with the fisheye port and 100 macro, for much the same reason as you, I wanted to travel somewhere with fewer ports. It would not focus. You could buy a diopter for your lens and no doubt you could make it work, but unless you can focus on the virtual image of the fisheye port, I think you'll be very disappointed. It is very close to being able to work I think, but still off. There is a romote possibility that working at F-22 might give you enough depth of field to catch the virtual image, but I surely wouldn't go on location counting on it.

 

While we are on the subject of macro lenses and domes, I have often used my 50 or 60mm macro lenses behind my fisheye dome. The reason being I wanted to be able to get close to medium sized fish and still get the whole fish, not a head shot like the refraction of a flat port might render. However, I don't believe I've ever been able to get 1:1 with my 50mm Sigma macro behind that dome, and I think it is because minimum focus happens at a point inside the port.

 

Just speculation on that point, but I know I can't get the same 1:1 magnification I would get with a flat port. I'm interested to know if Paul was able to get 1:1 with his 100 macro/DP95 combination. Paul ... did it focus through the whole range behind a dome port? I know you said you got clownfish, but did you try to shoot really small critters too?

 

Anyway, for so many reasons, you really need a flat port with your Seacam and 100mm macro, not the least of which is the ability to add the Wet Two diopter. http://www.seacamusa.com/wet-two-diopter.shtml

[Paul Kay 65]

Hi Stephen

 

Sorry I should have said that my set-up disobeyed all the rules in that my aim was simply to ensure that there was clearance between lens and port. I did NOT attempt to locate the lens at its optically correct position (ie exit pupil aligned with port's centre) and so the lens would not see the virtual image in the same way as if it was correctly aligned. With the set up I used the 105 simpy operated as though through a slightly curved piece of glass, and this is how I'd see it operating through a Superdome - with sufficient clearance for the lens to fit only. If there is too much air gap (which it sounds like from your test - I have not actually set up a Superdome and 100) then probably everything falls apart and the lens won't focus. With my set-up, the closest focus was slightly compromised and I doubt that I could achieve 1:1 but it wasn't restrictively far off. Image quality is surprisingly high.

 

I haven't looked into the optical theory behind what's going on, but the DP95/EXR35 does work with the 100mm usm macro with slight limitations. (For anyone interested, the 60 micro Nikkor also operates well behind Subal's small domes - I have a friend who used the DP84B and 60 for a long time with good results).

 

The DP95 is a neat little port and together with the extension tube 35, meant that I could carry relatively little and yet still use both 24/1.4 and 100/2.8 usm lenses - my favourites. Given airlines ability to break things, this is becoming a real issue, and I can squeeze housing/camera/lenses/ports/flash into a carry on bag (don't ask about the weight) JUST.

[michaelsweet 0]

thanks eveyone;) funny stephen i emailed liz to see if i could get a flat port before my trip;) than i see you here;) - if i end up shooting any macro it will be a first for me - clown fish size or bigger only - so far i only tried an 85mm (just to see) it would not focus in the superdome - their was to much space between the lens and dome i guess - i have a smaller dome that i can try (dp60 i think) - i think w/ 100mm and the size fish i will be shooting i won't have a prob w/ scratching my port or the subject - i ordered the lens hoping somthing will work;)

[Paul Kay 65]

The following example may help - one is the entire image which should give an idea of scale, and the other is a section of it to illustrate that the file is reasonably good. Unfortunately there is no focus distance within the EXIF data.

[michaelsweet 0]

wow - this would be more than perfect as i already have way to much gear to lug around (landscape gear has to come too) - i'll let ya know in a few days if i can get similiar results from the domes/extensions i have - this has been very helpful - i have one smaller dome - measures 6" across - guessing it's the dp60? i have an extension for it - which lens do you think i'd have the best luck w/ canon or sigma / 100mm or 105mm? - the minimun focus ranges from 5.9" to 12.2"(105mm) - i don't quite understand the focus distance/virtual image thing but i assume one of these has a better change of working?

[Paul Kay 65]

The Canon 100mm f/2.8 usm macro is excellent because it is an internal focussing lens. If you have this lens its the one to try. If you are looking to buy one - go with this one, its a stunning lens.