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herbko

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Posts posted by herbko

  1. Posted

    If that is, we get lens and port combinations capable of supplying the image quality required by such a sensor.

     

    If you believe the 105mm macro can achieve 12M pixel in a 1.5x crop, 24M on a FF shouldn't be a problem except perhaps at the corners. The 12M pixel 1.5x crop sensor has smaller photosite spacing which places greater requirements on the lens as your lens designer friend has pointed out.

     

    Here a good test report of the Canon 100mm on a FF

    http://www.slrgear.com/reviews/showproduct...duct/157/cat/10

     

    You can probably also get that resolution with a fisheye lens.

  2. Posted

    If the D3x is 24M pixels FF as most are forecasting, there's very little downside to using it versus the D300. Think of the 24M pixel FF sensor as having a 10.7M 1.5x sensor built in. Nikon will probably have a crop mode that will give you just that, but even if they don't you can always do it in PP.

     

    The obvious advantages are:

     

    You may at some point want 24M pixel.

     

    If you are happy with 10M pixel resolution you can digital zoom, your 105mm lens effectively becomes a 105 - 157mm zoom. It's actually probably easier to do this with a larger sensor than building a good 105 -157 macro zoom.

     

    The less obvious are:

     

    As Craig mention earlier in this thread, the larger sensor will give an advantage in the trade off between DOF and resolution versus the smaller sensor.

     

    Better signal-to-noise and dynamic range. At least more room to trade resolution for dynamic range.

     

    Shallow DOF if you shoot wide open. This is probably not often done underwater.

  3. Posted

    Is the "shoot in the mirror" test the best way to see if an optical slave is firing properly?

     

    I have a YS-110 hard-wired via sync cord and a YS-27dx that will be firing as a slave.

     

    If I set it up and shoot at the mirror and they both fire am I good to go? Does the highly reflective mirror make it "too easy" for the optical slave to pick up the light? In theory, are slaves triggered by direct light from the primary or the reflected light off the subject?

     

    Would I be better off shooting in a dark room at a big white wall and looking for the strobe patterns?

     

    Thanks in advance!

     

    I've had some fun and games with similar schemes. There are a couple of basic problems.

     

    One is that depending on the position of the strobes, you may be triggered by reflected light and underwater you may not get enough reflected light from your subject.

     

    The other is that under bright conditions the slave sensor may be saturated by the background light and is not sensitive to the trigger.

     

    I found the scheme to work pretty well in dark temperate waters and not very reliable in bright tropical conditions on wide angle shots.

     

    Test your system outdoor in day light and see what you get.

  4. Posted

    DNG is here to stay. I don't think Adobe will abandon it any time in the foreseeable future. That would really hurt their credibility. As long as Adobe remains a player in the imaging business the format will be supported.

     

    I'm not converting any of my Canon raw files to DNG. I don't see any advantages in doing so. There are far more raw converters for the Canon files than DNG, and I can alway do crw -> dng if I come across one that doesn't support crw.

     

    I am not loosing sleep over the possiblility that I'll see the day that Canon raw files won't be supported. The problem with DNG is that the biggest generators of raw files, Canon and Nikon, are unlikely to have native support for it. The result is that there are far more Canon and Nikon raw files than dng files and that will be the case as long as Canon and Nikon cameras do not have dng outputs. Third party software will generally have the best support for the most common format, so I expect the Canon format to always be better supported than dng. I think the smart people at Canon and Nikon knows this and are unlikely to offer dng outputs in the foreseeable future for this and other reasons.

     

    The bottom line is that I can alway do crw -> dng and not the other way. I see no reason to limit my choices.

  6. Posted

    James and Herbko,

     

    Every system has trade offs, however my comments regarding macro lenses at F/22 were based on the Olympus 50 mm F/2 lens. The only DPReview comment I have read regarding this lens is that it is one of the sharpest optics they have ever used. Since it only works on 4:3 sensors I would conclude that means it is better than the Nikon 105 and Canon 60 mm macros which have the closest AOV. They don't say just at F/11 or wider.

     

    Phil Rudin

     

    Look at the dpreview lens test of the 12-60 at 50mm, F/11 and F/16. Diffraction is basic physics. The 50mm F/2 won't do much better. Did you think that Olympus just did a poor job on this $900 lens. On a 10M pixel camera all 4/3 lenses will be the limiting factor at apertures smaller than F/8.

  7. Posted

    Phil: what you didn't mention is that at F22 you will have a lot of diffraction at f22 and the results from the D300 or E3 at F22 will be poor.

     

    Cheers

    James

     

    The dpreview lens tests show this clearly. The sharpness of the Olympus lenses drops rapidly at F/16. Diffraction limit their usefully range ( if you want good resolution ) to around F/11. To properly compare 35mm lenses and 4/3 lenses you have to factor in the 2 stops in the diffraction limited resolution.

  9. Posted

    all the reports of flooded inons i have read have been due to the yellow o'ring getting out of its groove when you close the strobe. you have to be careful not to twist it too fast and put just a little bit of grease on the outside so that it turns easily.

    hth /paul

     

    I haven't flooded one, but did notice that the yellow O-ring will stretch over time, no doubt from rubbing against the cap. If you keep grease on it and replace it every couple hundred dives, I think the risk of flood should be very small.

  10. Posted

    I can think of many underwater housing companies that are receptive to user feedback. Aquatica has been making continuous improvements in their housings, since they started going digital w/ the D100 housing and their compact housings. Some of the main things that I know they incorporated are that they:
    • Moved the control dials so that you can reach them from the handles
      Designed and implemented a magnified viewfinder
      Designed a port locking system
      Began offering a larger dome port

    Cheers

    James

     

    I would also add to the list

     

    6" dome port

    smaller auto focus only macro port

  11. Posted

    in layman's terms...aren't you splitting hairs so to speak. I remember the fellow that housed the large format camera underwater. The photos were very nice but really not any better in "usable" terms than a full frame photo. In the market that oly competes, it compares favorably with the big two and any difference you see in photos is almost negligible until you get to the higher ISOs. Even on DPReview the cameras side by side perform roughly the same despite the lens advantage given to Canon in the test (f1.4).

     

    In practice, resolution of macro photos are often diffraction limited by the small apertures used to get large depth-of-field and all good macro lenses of a given sensor size format will do about as well. I don't think any brand can gain an advantage in resolution of macro lenses.

     

    Larger sensors have a slight advantage over smaller sensors. I've only shot 1.6x crop and 35mm DSLR's, and have not made enough big prints from either to really have much of a feel of how big the difference is in practice.

     

    The motivation for my last post is just to put in context the often seen claim that Olympus has the sharpest optics around which in itself is not incorrect. However, it seems to me those who repeat these claims always leave out the simple fact that because a 4/3 sensor is half the width of a 35mm sensor, the 4/3 lens has to be twice as sharp to get the same resolution in the final image.

     

    Again in practice, most people will be happy with the resolution of any of the current systems, but I would disagree with those who recommends Olympus over others on the basis of sharper lenses.

  12. Posted

    It is true that the Olympus 50mm F/2 macro does resolve more lines/mm than 35mm macro lenses in that range which makes the claim that it's the sharpest optics around technically correct. However, that measure does not take into account the difference in sensor size. To capture the same details on a 4/3 sensor the as a 35mm sensor an Olympus lens has to resolve 2x the number lines/mm as a 35mm lens. In other words it has to be twice as sharp for the system to stay even.

     

    Taken as an overall package the Olympus system with that 50mm lens is not be best one for capturing the most detail.

  14. Posted

    Luckily, I don't yet feel the need for a magnified VF. :)

     

    Stu

     

    You're right about not needing those buttons underwater. However, I think it's likely that they'll end up moving quite a few things around to make room for the larger LCD and put in live view.

     

    I wouldn't say a magnified VF is a need. I'm fortunate to still have close to 20/20 vision. However, I wouldn't trade mine for all the new 5D II features on that list.

  17. Posted

    My first choice in flights to Asia is EVA Evergreen class, a nice big roomy seat for a little more over Economy class. I've used them for 4 trips to Thailand and Bali without any problems. The food is only fair, certainly not up to business class standards, but everything else is very good.

  18. Posted

    "I don't see how their behaviour would be altered and that they would start to associate humans with food."

     

    That's a far different statement that the one you made previously. Here's that quote again:

     

    "It is very unlikely that sharks are able to make that quite advanced (for animals) thought transition of an attractive smell to actually feeding."

     

    I don't think you're giving sharks enough credit. The crew of the Shearwater have noticed that the reef sharks will show up whether they chum or not. They, the crew, think that the sharks have been trained to associate the sound of the Shearwater's motor with food. On my trip we saw many sharks on the one dive where we did not chum. Of course I don't have a baseline for the number that usually show up at that reef. Someone should go and dive there off a sail boat and see if there are differences.

  19. Posted

    It's usable but hover color is still white and makes it hard to read against the light blue. An even worst problem is the sub menus are not offset enough from the main drop down which makes selecting the next item on the main drop down difficult. You have to put the cursor almost against the left edge to be off the sub menu.

     

    I made a slight change for IE5/6 so maybe thats why it works now for Deep6. Giles, is it working for you? Herb? This should not affect the color change on hover though. If it does, let me know :D

     

    Im downloading a VMware image that supposedly has an IE6 setup. That should help in testing that myself.

     

    Cor

  22. Posted

    My more serious point is that the continual new model scenario is simply not sustainable - I wonder if its worth starting a thread on who feels constrained (really constrained) by their current equipment. As far as I can see, a real move forward for underwater photographers with genuine visible improvements will only occur when ports are redesigned (non-concentric domes perhaps) or thinned (silicate glass?) or whatever - optics are now the constraining factor. I'm dubious that a new camera model will really do anything other than provide a nuance of difference

     

    The reality is that underwater is a very small fraction of the DSLR market. The rest of the camera buying public wants the latest and greatest technology when they shop for a camera and don't care much about minor differences in body shape and control locations. The camera makers will probably continue to replace their products with new models every couple of years driven by competition if nothing else.

     

    The problem this creates for underwater photography is that a 2 year product cycle leaves no time to refine housing designs. Since I'm new at this and never owned a refined film housing, I don't know what I've been missing, but I can't imagine this is a big impediment to photography.

     

    We can choose to get off the upgrade cycle any time. I'm with Steve. I'm don't plan to replace my 3 years old Canon 5D in the foreseeable future.

  23. Posted

    One thing I've wondered is why Nikon doesn't offer a setting where the camera generates the most bits it can for a given frame rate. Assuming it can do 8 fps at 12 bit and therefore only 2 fps at 14 bit, why can't I get 13 bits automatically when I set the camera to 4 fps? Seems obvious to me. 13 bits is a perfectly reasonable setting just as 12 and 14 are, and the TIFFs that result are always 15/16 bit regardless.

     

    It's probably 2 different A/D converters, 12 bit and 14 bit. You can't get 13 bits out of the 12 bit converter, and unless it's designed for it, you can't clock the 14-bit converter faster.

     

    P.S. Anyone who believes the D300 can't offer more than 9 stops of dynamic range and the A700 beats it by more than 2 stops needs to study up. I'd rather disqualify diwa labs as a source of useful comparative test data than to spend time researching why their data is so inconsistent.

     

    Agreed. That does not look believable to me. Wonder why dpreview hasn't reviewed the D300 yet.

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