Rob Kille

I am confident you understood from my previous comments that distance was set at 6". And that they are accurate. But if you question them please feel free to reference the website your clarkvision article cited http://www.dofmaster.com/dofjs.html , it's the same one I showed the link to in my first post earlier today I don't care about the underlying technology (which is not the same as saying I don't understand it), I only care about what the technology renders. And in the case of a DX with a 60mm lens vs. a FF with a 90mm lens, both at identical distance, aperture, shutter speed and ISO, the DX renders a greater dof. There is absolutely no legitimate argument to the contrary. None. It certainly is a red herring, and not only given your use of it in the comment I replied to but also because diffraction can vary dependent upon the lens in question. As you know, I never said it did. I said above F22 is the point where on a DX sensor with 60mm lens it becomes evident enough in the image to be concerning. Regarding your clarkvision article: it's quite the pedantic dissertation, don't you think? But it is no revelation. All he says is that there is a two stop disparity in dof between two cameras in his example "Another Way to Look at the Problem" and the bigger sensor camera has to decease light via shutter speed, aperture or iso, in order to make the images from each camera identical. And to offer support for his premise (that the 2-stop disparity exist before the adjustments to decease light) he cites the very same DOF calculator I provided a link to earlier today and you dismissed as the need to "grind numbers". And in most cases, forcing a decrease in light that is not necessary in the DX camera results in limiting the FF photographer's breadth of options. The bottom line is this: same fov and same settings on lens/camera on both a DX and FF camera results in a 1 to 2 stop dof advantage for the DX. Usually 2-stop, particularly at minimum focusing distances. Hey, despite your rudeness (why did you go there, by the way?) it's been fun discussing this with you and I wish you a happy and safe 4th of July.

Please look at the data below which compares dof at various f-stops for FF vs DX, for the lenses cited by loftus. As you can see DX at F22 (which is an aperture where diffraction is not visible in an image unless pixel-peeping) has a greater dof than FF at F32. For the purpose of this discussion there is no need at all to open up relative to FF if diffraction is minimized and dof maximized. What would be the purpose? FF (90mm) F32 = 1-1/4" F27 = 7/8" F22 = 3/4" F16 = 3/8" F11 = 3/8" F8 = 1/4" F5.6 = 1/4" DX (60mm) F32 F27 F22 = 1-11/16" F16 = 1-1/4" F11 = 7/8" F8 = 5/8" F5.6 = 3/8" But not the same DOF (not to mention that F11 as an initiation point for compromise resulting from diffraction on a DX sensor is a bit of a red herring) Given the way loftus asked the question, any other way of responding would not relate directly to the inquiry. If two cameras, one DX with 60mm lens and one FF with 90 mm lens shot the same image at the same distance would the dof be the same. The answer obviously is no. And opening up the DX in order to keep the results of diffraction not visible is pertinent only above F22. Declare a winner? I understood his question to be one of a comparative nature rather than one of "winner-take-all". I think I have said it here, that I believe FF is a better format than cropped, but I believe on a variety of issues the difference between the two is vastly overstated, or in the case of saying FF loses only one stop of DOF to DX....understated. Because DX renders greater dof field at F22 than FF does at F27 and F32, and above F22 is the point where refraction becomes evident (or should I say the results of diffraction) on a DX sensor, there doesn't seem to be a host of reasons why anyone would want to above F22 very often. 1-1/2" of dof is pretty significant at 6". Plus, the viewfinder on a DX camera begins to get a bit dark, at least where it is evident to my eyes, at F22 and above. The only time I shoot my D2x above F22 is when I get greedy (when I get greedy I tend to have no fear of rendering a crappy image ). I like limiting aperture in macro situations to f11-F18 because that **usually** renders sufficient dof, but not because I fear issues with diffraction at F22.

While I understand that this is a reality, I am not sure it is of such visible reality that one "must" open up. By and large I think much of the importance placed on the issue of diffraction (at least to the extent of what is being discussed here) is vastly overstated. I simply don't see it unless I engage in pixel-peeping...... ......but, even if one does agree that the diffraction (of the amount we are discussing here) issue is a major impediment to quality imaging I can't find any reference that suggests a 1 stop adjustment balances out the DOF disparity or eliminates the "advantage". No matter where I look for the comparison Loftus (Jeff?) questioned, the result is always similar to the following (I say similar because DOF is not quantitative). FX: 90mm lens @ f11 @ 6" = .03 ft dof (roughly 3/8") DX: 60mm lens @ f11 @ 6" = .07 ft dof (roughly 7/8") massive improvement over FX DX: 60mm lens @ F8 @ 12" = .05 ft dof (roughly 5/8") significant improvement over FX, yet reduces diffraction still DX: 60mm lens @ F5.6 @ 6" = .03 dof (roughly 3/8") equals FX at arguably image quality preferred aperture Some of my references are as follows. Now, I understand there is a lot of crap on the web so I seldom buy into anything I read on it, but my understanding of how and why DX offers better dof is in line with these sites, but if I am wrong it sure would be nice (in earnest) to have someone take it apart and teach me a thing or two. http://www.bobatkins.com/photography/techn...fcalc.html#calc http://www.dofmaster.com/dofjs.html http://photoinf.com/Tools/Don_Fleming/Dept...Calculator.html

Hmmmm.....my understanding is different from James' so I think I'll have to look into this a bit, but my belief has always been that 1) for any given reference, the CoC of the DX remains roughly 2/3 the size of the FX so the advantage (for the given focal lengths you cite) remains, and 2) the lens properties still matter so the wider lens would deliver greater DOF to start with

My apologies, I thought it was you who made that post along with the cited image. I guess my memory diminishes as my age increases

I think there are definite advantages to FF, though for underwater work I do not think they are determinate. Because the noise issue is just so much more pronounced topside where ISO options can have such a bigger impact, I think for most topside work FF has it all over any cropped sensor. But underwater, where I shoot base almost always and would regardless of sensor size, I prefer the DX. Some FF shooters (those with big MP) do have the advantage of missing composition, yet perhaps being able to crop back to good composition because of the massive amount of data the MkII/MkIII shooters are working with. Those of us with DX sensors need to be pretty much close to spot on because we do not have the same amount of pixels to cut from an image and maintain a viable amount of info. D3 shooters are in the same boat. Massive resolution on FF certainly isn't a burden But with so many people these days trying get their images in camera, I don't know that this particular advantage is of the *satisfying* variety. I read with interest James' comment about working underwater, where he described moving back, shooting and then cropping with his FF rig (in order to render greater DOF but with a closer than shot perspective). But my first thought was this adds water between the subject, sensor and strobe(s). I kind of dislike saying this, but in my experience it will only result in softer less saturated images than being physically closer to the subject will. This is an advantage topside for the big MP FF sensors, but underwater I believe it is rife with compromise. At least if we expect our images to stand up to critical review by ourselves or others. In this case I think James is guilty of Mega Pixel Abuse. I look forward with interest to the D3x (or whatever) because I do want to shoot FF topside and would prefer more resolution than the D3 offers, but I don't know that I will house that camera in place of my D2x/Seacam rig. And that will save me from buying the extra D3x for redundancy as well as the new Seacam housing. Conservatively that's around a 10-12 grand savings, or a couple extra Indo trips. So for the near future I am very likely to stick with my D2x/D2xs/Seacam combo, and simply buy whatever Nikon FF camera ultimately catches my eye and satisfies my topside needs. James hit it right on the head......it is very nice to be at this point in time where aficionados of each brand to have the option, or combination, of both crop and FF sensors

..blaming it on the housing, are you? I resemble that!

Hi Bruce, I don't shoot Canon but the Wet 2 and similar focal length, in my case D2x with 60mm, has been my go-to macro set up for about two years now. I like it for subjects as small as pygmies or as big as anemonefish (hey, we all shoot them....why not admit it ) but not anything big enough to make me step back a foot or more, like a medium sized frogfish. In my experience CA has not been an issue because I suffered CA as bad as that in your seahorse image when shooting a couple pipefish sticking their heads out of some white coral (open background, not black,SS @ 1/80, and aperture at f25) in PNG in 2006. So I did a little layman's experimentation to see if it was something as simple as the physical setup of my camera/housing rig or something inherent in the diopter's performance. What I found is that the alignment of the lens to the flat port, and the Wet 2 being pushed all they down against the flatport glass, is critical to the avoidance of CA. It took me a while to figure this out because without the wet diopter it never really mattered if the flat port was not effectively perpendicular to the lens axis, but I can both create CA and eliminate/mitigate it by dictating whether or not the Wet 2 is effectively perpendicular to the lens axis. This probably doesn't matter to other wet type diopters because they are not achromats, but I suspect the fact that both the Wet 2, and the 60mm, or in your case 100mm, lens are achromats, it does matter when using the Seacam diopters. Now, not a bit of that is based on science but it is what I found when figuring out how to make the combo as productive as possible. Perhaps someone with an optical background could weigh in.

My problem this article is that his argument is predicated on the supposition that demand is driving the price of oil higher and that as demand weakens and supply strengthens, prices will fall. Everything I have heard recently is that many producing countries are actually banking oil because they have no customers to sell it all to. Iran, Russia, Venezuela are examples, and in the US we export just below 2 million barrels of product (gasoline, diesel and jet fuel) per day, that is refined from the oil we import. That is also why the Saudi's told Bush to go pound sand when he asked them to ramp up production. They understood it would not have any effect on price because there is already more than enough oil on the market to satisfy all the demand. James is right, in my book. The price of oil is currently driven by a financial rather than economic dynamic.

I've been involved in the oil business for much of my career, mostly hot mix or emulsion sides, but oil nonetheless. Here is what I know to be true about gas and diesel prices, today: Diesel, even ULSD, is significantly less expensive to produce, for reasons that range from the crude origins to the distribution platforms. One example is that some of the byproducts created from the refining of gasoline from oil (normally expensive to dispose of) are used in the production of diesel. Now one could make the claim that this reduces gasoline costs, but clearly it is an advantage net, resulting from diesel production. On the current US market big oil recieves gross profits of about 6 bucks per barrel of gasoline vs 32 bucks per barrel of diesel. The reasons diesel is expensive at the pump is because it is immensely profitable and used by only a sliver of the US population. They can reap windfall-like returns without angering any more than a small percentage of the population. By almost any cost analysis or production calculus, the cost disparity at the consumer level should be favorable to diesel. Energy output from diesel eclipses gasoline and it is cheaper to produce. If we are going to stick with fossil fuels until the earth can give no more, we ought to be doing it via the diesel lines.

On the other hand decent (not great or total) medical coverage for a family of 3 costs $700 to $ 1,200 per month in the US. I don't know specifically how your tax revenues are distributed but I imagine you have significant social/economic programs at your disposal as a result. Significant in the sense that they do not exist here, I enjoy the eat-what-you-kill nature of the US society, but the inequities for many here are very hard to dismiss. High fuel and food prices and no medical for the family. That's a tough nut for many here, not only financially but intellectually and emotionally. I'd imagine some of them would willingly be exposed to VAT or use taxes on discretionary spending if it would bring medical and pharmacutical coverage to their families. I am pretty liberal, though not of the bleeding heart variety ,and I don't personally want to suckle from the government teat. But man do European countries do a better job than we do in providing social advantages for the distressed, or for that matter everyone else too.

Drew and Dave, thank you for the welcome, ------ and the warnings! Fortunately I am not as "jumpy" about new gear as I used to be The D2x has it's shortcomings, but in general I agree with Alex Mustard's comments about this particular platform and the level of appreciable improvement realized by moving to one of the current bad-boy cameras on the market. For macro I like the crop sensor, 60mm and a Seacam Wet diopter (I have found that to be a very productive combination) and for wide angle the DX does mitigate, to some extent, corners issues. I like rectilinear lenses more than FE so when thinking about moving to FF this is a significant consideration, for me. And since I still appreciate base ISO more than higher ISO's, even on the current ISO champs from Nikon and Canon, that isn't specifically something that would cause me to drop another 10 or 12 grand on camera and housing. Still, while I enjoy the D2x underwater it's shortcoming do bother me topside. I imagine I may end up shooting something new topside and something "old" underwater. Years past, when I couldn't really afford these kinds of costs I had little compunction to spending this kind of money. Now that I can afford them I tend to be more circumspect. I imagine that all has something to do with youthful stupidity vs. fearful middle age

Hello all, my name is Rob Kille. I've been shooting uw for a while now. Like many of you I took the progressive route to my current setup (D2x in Seacam), from Nikonos to SLR to DSLR. My preferred destinations for uw-photo are Indonesia and Papau New Guinea but I have not yet cut the pull Galapagos has on me. I don't dive the Caribbean much anymore with the exception of Bonaire which I enjoy as much for the topside atmosphere as I do the diving. I get out about 4 times per year for dive trips, so considering how fast the game and equipment are changing these days Wetpixel seems the appropriate place to try and keep up Hopefully I can give something back as well. Rob