Posted by Tom_Kline
on 03 September 2018 - 01:34 PM
The way blackwater dives are done at Kona, Hawaii there are no lights other than the ones held by the divers and a deck light used for gearing up (this may get turned off when everyone is in the water but the captain). Lights are used, however, for other blackwater operations - maybe the top source of light in some of the vids linked above.
Diver held lights are enough to attract squid and dolphins feeding on the squid on some dives from my experience. Potentially sharks too but I have yet to see one. I have seen vids being done on a few of the bw dives I have been on in Kona - the lights were attached to brackets in the usual way, e.g. Ultralight arms and trays. I have also seen a Gopro used with lighting provided by a handheld light (bright one provided by the boat - which I always refuse as all mine are attached to the housing but I am only doing stills).
The FTZ does NOT support screw-drive type AF. It might be possible for someone to develop one that does, either Nikon or a 3rd party. However, it might turn out that the communications protocols in the new Z cameras will not allow this, e.g., adapted lens AF is too slow (such as changing focusing direction).
But..... there is another alternative that seems more interesting to me. That would be to develop an RSTZ adapter for manual-focusing-only with Nikonos RS lenses like done on the RS camera bodies. This would require an adapter with a the screw drive in it but instead of communicating with the Z camera body, it would communicate with an RS analog control switch on the housing (e.g., with a cable)!!! If I recall correctly the RS manual focusing switch controlled focusing speed as well as direction. Therefore a functional analog (to the RS) would be preferred. This hypothetical RSTZ adapter would obviously have to be paired with a housing that came with this switch.
I just bought the zen 230mm for the 16-35, and I am in the same crossroads as you are, dont know if It is a better choice sigma 15 or nikon 8-15. I know the sigma doesnt need anything extra, but the 8-15 needs a zoom gear on my nauticam. If I get the 8-15 will the shades of the 230mm dome show up in 8mm?? Do I need to get the 100mm dome for it?
Yes, the shade will be seen in 8mm pix. At 8mm the angle of view is almost 180 degrees all the way around the image and not just at the diagonals as at 15mm. Find out if the shade can be removed - many can.
Tim! I appreciate your reply and honesty... I have been spending so much time trying to justify the costs of everything that I was making the wrong decisions.
Today I ordered the ZEN 230 Glass Port for the 16-35 and bit the bullet... Not point in doing it wrong right? Your reply came after I ordered it (and after a bottle of wine) so that helps me feel better about the decision...
Next I need to figure out what Dome to get for the 8-15 but that is less of a rush for me.
You can use a large dome with the 8-15 fisheye. In fact the results will be better than with a smaller dome. Even with just 12 Mp and the smaller DX format I got better results (as in sharp all the way to the edges of the frame) with a superdome compared to all the smaller ones.
The distance to the dome I was referring to is the subject to dome distance. The virtual image surface shape is a function of focused distance, only spherical at infinity. This is probably why small domes work for macro subjects where the dome is very close to the subject so the virtual image is flatter. Note that this thread is > 3 years old whereas FE question is new.
And for a subject at infinity the virtual images lies at a point which is 4 x the radius of the dome from the centre of the dome which is where the principal point of the lens should be positioned. This means that the centre of the mage is at 4R but because the virtual image is spherical, depending on the lens's angle of view, the edge of the image will be somewhere closer - exactly where will depend on its position and the dome's radius (radii) and thickness and refractive index - its complicated. But the camera lens is not much of a factor here because it can only image what it 'sees'. Its ability to do so will be dictated by the virtual image produced by the dome port and subject and any inconsistencies of the camera lens such as field curvature at closer focus. Its all a bit messy.
The 'less curved' dome idea is in effect the suggestion of positioning the camera lens closer towards the dome as opposed to ensuring it is aligned at the centre of the dome. You may want to try doing just this (should be easy enough). If I remember correctly, I think that you will find that it results in the trade off of reducing the field of view as opposed to doing what your diagram illustrates so is counter productive.
Sadly I suspect the 'filmdays' rule of thumb of 90 degrees being the maximum viably/easily correctable field of view still applies with dome ports though bigger does help .....
I still disagree about the unpredictability of lens performance underwater behind dome ports. Its lack of technical information which hampers prediction nothing else.
I too am a long time LR user, since version one. I do not think there are any other programs currently doing digital asset management (DAM) to the degree that LR does. I probably spend more time doing DAM work than post-processing; entering keywords, titles, captions etc. This may not be important in the beginning but once you have a large number of images, e.g. I have about 1/2 million images in my LR library, it is indispensable. It is a very good idea to work on DAM from the beginning!
They are currently doing a LR boot camp. The basic stuff was last week. There are 3 weeks to go including this week that are more advanced but there is some re-capping of earlier material as well. It might be well worth your time, about an hour or so each work day to watch these. Each day's lesson gets repeated until the start of next day's lesson to accommodate time zones around the planet. It is free during the live broadcast (next three weeks). The previous week's material is presented again on the weekend.
I have been watching it and have learned new stuff even though I am an old hack at it. For example, I did not know about customizing the bottoms of the side panels - I now have my logo there. I do not agree 100% with the way the presenter, Ben Willmore, uses LR, such as how he sets up his folders. This is largely due to some of the peculiarities of the way I work. Nevertheless it is a very useful class to watch and learn new stuff.
I have the same problem as well when shooting salmon in streams using ambient light. There is a fair amount of drifting debris. Bubbles can be a problem (as just suggested) as well. Shooting with a fisheye lens at point blank range helps to minimize the problem. As well, it is best to avoid shooting into the light. Sometimes one does not much of a choice other than not shooting at all.
(easier for me to find image on my site). Note the light blotches in the water column. I see a dark one too (left side), probably a twig. Not too bad backscatterwise at the spawners that were real close. I angled the camera to avoid shooting into the sun - this gave the reverse perspective from many of my other shots - but easy to see the eggs emerging from the female from this angle! A downside is that the housing cast a shadow on the bottom (shot taken less than 2 hours from true noon).
Posted by Tom_Kline
on 26 December 2017 - 09:58 AM
I wonder if the FIX / upgrade to solve the TTL issue on the UWT circuitry be an easy fix?
The RETRA strobes will not be able to do any sort of wired TTL. There are just TWO contacts in the wired bulkhead. They are for basic flash synchronization, nothing more. There is thus no Nikonos film style TTL as found in older strobes. Therefore the various converters for using Nikonos TTL will NOT give you TTL!!!
Posted by Tom_Kline
on 09 December 2017 - 03:18 PM
Adam, would be great to get a direct comparison against the RETRA as the cash is burning a hole in my pocket and not sure which option to choose
I took some pix to address your question. The Inon Z220 shown in the pix is the model that preceded the 240 and now 330 is the same form factor as the newer models. The Seacam 60D also shown is another new strobe for 2017. Maybe we should call 2017 the year of the underwater strobe! As well, there is a new J version of the Sea and Sea AA battery model - I keep wanting to call it R2D2 but that is not the correct name. All these new strobes use AA batteries. We just got a foot or so of rain (with storm and gale force winds) so the snow is all but gone (why not in pix) - air temp right now is 8C.
Posted by Tom_Kline
on 03 December 2017 - 03:19 PM
f/4 to f/5.6 is a full stop not f/5. Closing down by one full stop is halving the amount of light passing through the lens so requires a doubling of the ISO to compensate if you keep the shutter speed the same. BTW I use auto-ISO in combination with aperture priority auto-exposure quite a bit for my non-flash underwater photography. This is because of the need to keep the lens stopped down to work OK with a dome port.
Posted by Tom_Kline
on 28 November 2017 - 05:39 PM
Fisheye lenses seem to tolerate being displaced from the dome's center of curvature. For example I got better corners using the Seacam 9" diameter Superdome, which is a hemisphere segment, than the Seacam full hemisphere but smaller diameter fisheye port with my 10.5mm fisheye lens even with just 12 Mpix (D2x camera). Seacam does not specify curvature radii.
This website has some interesting cartoons showing how the position of the entrance pupil center as well its disk diameter (line) shifts with angle. It is forward (inside the front element) with the 10.5mm fisheye (scroll almost halfway down the page to see this) at 90 degrees. The 15mm rectilinear example is very interesting as well (scroll way down). It shows the entrance pupil shifting towards the lens' rear with the line going beyond 90 degrees from the optical axis. The 28mm shift is not as radical (last example on page).
I have used the Canon 8-15 at 12mm (APSH) and 15mm (FF) with the Seacam Wideport quite a bit for close up shots (salmon in streams). The Wideport thus used is better at smaller stops. The Wideport probably has a smaller radius of curvature than your Nauti 180mm.
Posted by Tom_Kline
on 16 November 2017 - 03:57 PM
Nice report! Were you using Eneloops?
I guess one will have to learn how to hold the battery cover in one hand while swapping out the batteries - maybe wedged between fingers or cupped in palm with one finger allowing use of the other fingers? I have done this while swapping out batteries with rig in very cold (barely above freezing) stream (strobe was above water allowing for battery swap).