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Member Since 07 Nov 2004
Offline Last Active Today, 10:40 AM

Posts I've Made

In Topic: Minimum focus distance question

11 September 2015 - 07:08 PM

I'm using the Canon 14mm (2.8) and an Ikelite 8" dome with 4" extension.  I will post a pic of the rig on Monday - unfortunately I can't get to the office this weekend!

 From what I have seen on line of the EF14mm lens used under water the 8" dome is a problem. The lens is quite marginal when used under water with even larger ports such as in the Nauticam link I posted above. Sorry for the bad news.


In Topic: Minimum focus distance question

11 September 2015 - 07:02 PM

Here is a link to formulas that might help you work out the problem for a finite object distance.


You might try and locate a copy of Gomer McNeil's book  Optical Fundamentals of Underwater Photography. There are several pages worth of formulas and worked out examples. It is important to know that for a flat subject at a finite object distance the virtual image and focused image are both aspherical (shown in the book in final figure of the appropriate chapter). It will be very difficult to impossible to get the corners in your pix to be in focus if the center is in focus. That said there seems to be a great deal of variability as to how far out of focus your corners will be due to differences in individual lens designs and how they interact with dome port optics. It appears that the new Canon 11-24mm may be much better at 14mm than the 14mm EF prime lens, which works rather poorly. We need to see more tests of this lens as it will be very expensive to use since it requires special ports due to its large diameter. See for example: http://www.nauticamu...support-testing


In Topic: RAW converters

27 August 2015 - 01:12 AM

Very interesting. I have yet to use DPP even though I have shot tons of Canon so did not know this. The result you get adding +40M as a preset is different from using a uniform color addition with the slider tool per your comment above? This little project was my first time doing this but looks like something to keep in mind for future UW color correction. My biggest issue, however, is stained water which I find very challenging to fix in a satisfactory way.

BTW I noticed that even within the normal slider range there can be some nasty artifacts, particularly with clarity.



Yes. The solution is to make a profile with a higher Tint starting point. This one was called 40T - as it adds an extra 40 units of Tint before you start using the Lightroom controls. 


String’s problem is that Canon cameras in particular can add more tint in camera (more than +150) than you can in Lightroom (limited to +150). DPP supports this in the Canon RAW file. Lightroom does not. It is why I always tell Canon shooters to use RAW + JPG when shooting filters. Or use this work around. 


You can also achieve a similar affect with the sliders in the Camera Calibration module - but I find them fiddly to use. The Custom profile solution is one click simple and it s stored in Lightroom for future use. The profiles are Camera specific.



In Topic: RAW converters

26 August 2015 - 11:02 PM

I just remembered there is a way to increase the adjustment range. Insert and pull down the gradient tool all the way and select the change you want from the menu. I picked the color thing on the bottom and added a bunch of magenta. Not the exactly the same result as what Alex did but you should get the idea.

In Topic: RAW converters

26 August 2015 - 10:10 AM

Here is a version of the turtle unprocessed and processed in Lightroom and only in Lightroom with a few clicks - (this is just a virtual copy of the original file):



So what exactly did you do? I gather something beyond the tint slider since it was already at the maximum setting.