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markdrayton

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markdrayton last won the day on September 24 2018

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About markdrayton

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  • Location
    Cardiff, Wales, UK

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    United Kingdom
  • Camera Model & Brand
    Nikon D7000
  • Camera Housing
    Nauticam NA-D7000
  • Strobe/Lighting Model & Brand
    2 x Inon Z240
  • Accessories
    ULCS strobe arms

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  1. Walt, I think youll find its an extra 20mm extension thats needed with the Kenko 1.4x TC
  2. Hi aviator8. Are you sure those gels you are referencing are optical gels? They look like lighting gels to me - 20x24 inches. If so, they aren't suitable for use as barrier filters in front of a camera lens. They are designed to be placed in front of theatre or filming lights. Of course Lee and others do make a more limited range of optical gels but they are far more expensive.
  3. As the visible light spectrum is usually regarded as starting at 400nm, if the UV torch truly produces a point wavelength of 385nm, no barrier filter would be needed. In practice, the light is likely to emit a spectrum of wavelengths extending to some degree into the visible range and so will be detectable both by eye and the camera sensor. (Do you see blue light when it is in "UV" mode?). The extent and intensity of this spread into the visible spectrum determines the need for yellow (minus blue) filtration. Wratten 12 filters have a sharp cutoff at about 500nm. Many lights designed for underwater fluoro photography actually produce a spectrum peaking around 455nm - visible blue light. This is because that higher wavelength is a more effective fluoro excitator than shorter wavelength true UV. Of course a downside of barrier filtration is that any fluoro effect below the cutoff frequency (say 500nm) will be lost. However without barrier filtration, lights with significant emission within the blue visible spectrum will tend to overpower the relatively weak fluorescence with their directly reflected blue light.
  4. Hi aviator8. The yellow barrier filters used in partnership with blue excitation lights for underwater fluoro photography are typically a deep yellow Wratten/Tiffen 12 or other manufacturer equivalents. I am not aware that Cokin make a Wratten 12 equivalent - I understand that their 001 yellow filter has a different spectral curve. The precise results are liable to depend on the spectral composition of your blue video lights. Some photographers prefer to use yellow filters and masks produced by their blue light manufacturers to ensure an appropriate matching of light and filter spectrums. Firedive (https://firedivegear.com) produce custom yellow filters and masks that deliberately let a little of the blue excitation light through to the camera. This usually results in a deep blue as opposed to black background and slightly cooler images as the returning fluorescing green/orange/red light is mixed with some blue. Whether or not this is better than the more usual Wratten 12 filtration is down to personal preference. Obviously for accurate preview of the scene, yellow mask and camera filters need to match. To accurately preview the results underwater on camera, you need to flip the mask up to view the LCD screen. The fluorescent light produced by marine organisms is usually orders of magnitude less than that produced by normal reflected light so you will need to use high ISOs, particularly if you want to bring out the subtler oranges and reds that tend to be lower intensity than the prevalent fluoro-green. This also makes close-up photography easier than wide scenes where it is difficult to get large amounts of light onto the subject matter. Still shooters will more easily produce good quality results using blue excitation filtered strobes. Mark
  5. As I said, functionality varies from camera to camera. Sony introduced an option to link spot metering to flexible spot focus mode on the A6500 (which my wife has) but not the A6300. No, but the Sonys do have a flash-lock function (FV lock) that can be assigned to a button. Can't say I've used it but as I understand it, it allows a TTL flash exposure value to be calculated from a pre-flash and stored and then recalled following recomposition as often as you like. Might be useful in some circumstances, but perhaps that would negate much of the theoretical advantage of TTL?
  6. Adam, I think it's more complicated than that. While it doubtless varies from camera to camera, my understanding for the Nikon D500, is that the spot metering zone relates to the focus mode. Spot metering locks a small metering area to the centre of the frame only when Auto or 3D focussing modes are engaged. For Manual focus, Single Point and AF-S Dynamic Area, it is the user selected focus point that determines where the metering zone is centred. For Dynamic Area AF-C and Group AF-C, the user selected focus point initially determines where the metering zone is centred but the camera may move both the autofocus point and spot metering zone if it detects that the subject has moved within the frame. So for spot metering without AE lock, you are only limited to where you place the subject in frame in Auto or 3D tracking focus modes. Returning to TTL, my understanding is that engaging spot metering on the D500 alters the TTL algorithms used by the camera so that it no longer tries to balance the strobe output with ambient lighting of the whole scene but instead, adjusts the strobe output to correctly expose what it thinks is the main subject - i.e. the subject material around the metering spot. Where the metering spot is relates to focus as above. Again, the detail of this complexity probably varies from camera to camera. Mark
  7. Most of these kit lenses extend considerably with zoom. I expect at worst, some lenses may collide on zoom with the WACP and possibly cause damage unless used with a long port extension, in which case they may not perform well optically at the wide end. I have also read that lenses with smaller front elements - slower aperture - work better optically with the WAPC. Maybe someone from the Nauticam world can comment as this is relevant to potential use with the new Nikon Z series where there is a narrower range of autofocusing lenses?
  8. I think you're confusing two Z7 functions. It is the "Low light AF" custom function that increases low light autofocus capability from -1EV to -4EV. This is not an assist light but works with internal electronics at some expense of autofocus speed so should only be used in extremely low light situations. The "AF assist illuminator" on the other hand may be used in low light and outside a housing does shine a green light onto a close subject. As with most other housed cameras, I doubt that the assist illuminator will be useful underwater, but this has nothing to do with the Z7's inherent low light autofocus capability. Incidentally, neither of these functions work with AFC mode. The D850 and D500 DSLRs low light autofocus capability is better than the Z7 by specification (-4EV central spot and -3EV for the rest) and as far as I know this is available in AFC mode. -4EV corresponds to half-moonlight illumination so extremely low light and may be a lot darker than most of us try to autofocus even underwater. However, in his Z7 field report, Nikon Ambassador Marcel van Oosten suggests that the Z7 Low Light AF accuracy in AFS mode is even more accurate than with the D850. He does also say that from his limited experience (using pre-production firmware), that AF is in general not as fast as on a D850 and that tracking a moving subject is more challenging. Mark
  9. I agree that the Sigma 17-70 Macro is no Jack of all trades underwater and certainly not a good underwater macro lens. However it does retain a useful specific but more occasional role in my lens collection as a flexible fish portrait lens. It has a good reach for shy creatures but also allows you to fit in all but the largest species that allow closer encounters.. Mark
  10. Hi Mark. I cant offer personal comparative experience with the Nikon 10.5. I would suppose that as a much more modern and expensive lens, the 8-15 might be optically better, but of course as a zoom lens, design compromises will have been made. These compromises arent obvious to me in underwater use. Regards, Mark Hi Mark. I cant offer personal comparative experience with the Nikon 10.5. I would suppose that as a much more modern and expensive lens, the 8-15 might be optically better, but of course as a zoom lens, design compromises will have been made. These compromises arent obvious to me in underwater use. Regards, Mark
  11. Hi Mark. Optically, the greatest difference is substantially less chromatic aberration with the 8-15. Subjectively, the lens is also significantly sharper. As expected, these differences are more pronounced towards the edges of the image. A downside is the reduced useful zoom range on DX meaning less reach. If youre not careful It is also easy to waste a few pixels by zooming out too far and cutting off the corners. These issues can be avoided by using a Kenko 1.4x teleconverter although this does sacrifice a few degrees of coverage at the wide end. Optically this combination works well behind a dome. When I last looked, no manufacturer offered a zoom gear for the combination so I use the standard Nauticam gear and a removable collar that provides the necessary extension. For me the image quality improvements far outweigh the minor downsides and I have retired my Tokina. Regards, Mark
  12. Yes, me too. A thread from the Strobe neoprene jacket caught in the O-ring. Salt water rapidly entered the Strobe body itself from the battery compartment. It is not fully sealed. Maybe gas pressure from the short-circuited battery cells is what does it? Mark
  13. This warning by Panasonic doesn't appear to be new. Here's a link to a thread that's 8 1/2 years old, discussing Sanyo's then recommendation that Eneloops should not be used in waterproof lights: http://www.candlepowerforums.com/vb/showthread.php?243109-Eneloop-s-safe-in-Waterproof-lights There must have been very many Eneloop cells used in underwater strobes since then. It would be interesting to know what are the circumstances of use in strobes that might lead to hydrogen venting. I would suppose that any increase in pressure within a sealed battery compartment might be a greater functional concern than a risk of hydrogen conflagration when the gas is released?
  14. Hi Kirsty, Welcome to Wetpixel. Like you, I have usually used the second slot for backup. With the D500, in this configuration write speed is limited by the slower card i.e. the SD slot. For most underwater shooting, the large buffer and the limitation of strobe recycle time on high speed shooting bursts means that the SD card write time isn't a real limitation. However, there could be occasions when shooting longer bursts of fast action, using natural light or possibly low strobe power mean that you would like to clear the buffer as quickly as possible. Usually these situations would be predictable and it's easy to switch second slot function on the fly. If needed you could then back up to the SD card in retrospect. I don't think there's a right answer to how to configure the slots on a D500 - it depends on your shooting preferences. Life just got a bit more complicated compared with the D7200. Of course the advantage of an XQD card isn't just write speed. Read speed is also potentially higher so uploading images should be faster as long as you don't have a bottleneck somewhere else in your system. Mark
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