Jump to content

Paul Kay

Industry
  • Content Count

    1791
  • Joined

  • Last visited

  • Days Won

    5

Paul Kay last won the day on September 5 2017

Paul Kay had the most liked content!

Community Reputation

29 Excellent

About Paul Kay

  • Rank
    Giant Squid

Contact Methods

  • Website URL
    http://www.marinewildlife.co.uk
  • ICQ
    0

Profile Information

  • Gender
    Male
  • Location
    North Wales, UK

Additional Info

  • Show Country Flag:
    --
  • Industry Affiliation
    Seacam - UK & Ireland
  1. Since you have to correct 'underexposure' then its a cause of noise in an edited image. Its actual effect varies depending on how much an image has to be adjusted and which tones need the adjustment. ETTR (Exposing to the right) introduces tonal discrepancies in my experience - its not a solution but is touted as 'data acquisition maximisation' (and supposedly produces a more malleable digital file). Its simply not that simple in my experience - I've tried innumerable methods of exposing and its best to exposure for the image you want rather than apparently maximising data capture. 'Sharpness' is a function of many variables, exposure is just one. It doesn't matter much, except when all the others are additive. FWIW the camera I have found to produce surprisingly 'malleable' files and respond least badly to hauling up shadows has been the Leica M9 with its full frame CCD sensor. Not usable underwater and 18MPixel only but surprisingly effective. I find the Sony A7II can be good but then again it can be disappointing - I suspect this is down to tonality problems which I don't always find fixable in post processing. As always depends what you are doing - I have been printing to 30" x 20" for the last couple of years, which is a reasonable size, and discrepancies can start to show.
  2. Incorrect exposure increases noise and thus affects perceived 'sharpness'. Exposing to the right also, from my testing over many years, is, in effect, often incorrectly exposing the image (or effectively parts of it to be more accurate), and depending on specifics can have a similar effect to incorrect exposure in that noise levels can marginally increase in some areas. I am an advocate in shooting 'within latitude' and this 'latitude' needs to be assessed for each camera - some have greater 'latitude' in terms of exposure than others. All that said, choice of apertures, movement (even with flash/strobe illumination at times) and precise point of focus are usually more significant.
  3. If it was a simple, single reason then this wouldn't be a problem. 'Sharpness' is in itself a non-technical and rather wooly term, so firstly you would need to define what exactly you mean by it. Then there are numerous factors which affect our perceived degree of 'sharpness' in an image, some relatively easily defined (poor exposure leading to noise, use of too small an aperture resulting in diffraction limitation, etc.) but others are not (lighting, point of focus, etc.). So its not easy to explain the physics.
  4. These two are my personal equipment and I've had them for many years. They have been very reliable and are still working well with long burn times. However I no longer need them as I don't shoot video currently and so its time to pass them on as its pointless leaving them on the shelf. I'm open to offers on the pair. They both have 1"/25mm balls fitted for use with arms and there are 3 x chargers included with them. One is blue the other silver and condition whilst somewhat 'used' is good in that there are no signs of anything other than the 'patina' of reasonably careful use! Shipping will be added at cost and as they are not light a UK buyer would be preferred.
  5. I've been trying this lens out. Firstly on a Canon D60 then on a Sony A7II via a Metabone adapter (a MkIII). Although conditions were good for around here (in the Menai Strait), they may not be considered so elsewhere! Anyway behind a Seacam CompactPort with my best guestimates for placement, the lens works surprisingly (as in very) well. It can actually focus on the dome so its close focus ability is good and focus speed (on both cameras) is fast. Here are a couple of shots: First is at about 13mm on the D60 (single Seaflash illumination): and second is off the Sony (vis had dropped) and is slightly cropped because of vignetting caused by the MkIII adapter although it probably will cover full frame from 13~14mm upwards. This lens is quite cheap and from my tests it looks like its one well worth experimenting with more. More pix on Facebook.
  6. 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.
  7. Sorry Marco but I simply don't know. First you will need to check if you have any circuitry in your Seacam housing - it may be fitted already - it will be under the metal cover in the 'prism housing' part of the housing and is accessed by one screw. If so then the housing will support dual TTL with Seacam strobes, but I can't give you any information about compatibility with Inon Z330. You may need to remove the circuit board if its not compatible. I suggest that you post in the dSLR section here on wetpixel. If you don't get any answers then contact your Seacam distributor (http://www.seacam.com/en/contact/partners/europe/seacam-croatia-slovenia) or Seacam direct. You will also need to check the Inon specifications - its possible that a fibre optic solution may actually be better and Seacam offer an Optical Slave Trigger at around 280 Euros too. Sorry not to be able to tell you but there are now so many combinations that I tend to deal with them on the basis of needing to when they arise.
  8. OK, some info. The price of the S6 (M) to N5 (f) adapter from Seacam is in the region of 180 Euros including tax (this is vat at around 20%) so its not as expensive as most Seacam S6 fitting cables but it isn't that cheap either. Be aware that you will lose TTL potential if you go for N5 cables. The 'newer' S6 sockets fitted to housings like the D800 have the spanner flats on their inside (this makes their external profile lower). I have an expensively specially adapted spanner which Seacam supplied me with to undo the sockets without causing any damage - its possible with an ordinary spanner which fits correctly, but not so easy and it can cause damage if it slips. I am wary of suggesting that you remove and refit sockets without the appropriate tool unless you are confident of the care you can take in doing so. (The good bit is that the internal cables clip on and off the circuit boards using a simple connector) Also appreciate that S6 connectors are (in my very practical experience) far more reliable than N5 because their design is fundamentally different and they are being used for the job intended. N5 connectors are being asked to do far more than their original design brief and their Achillies Heel is the two sprung pin system which causes grief if their is any ingress of salt water - I have replaced numerous N5 sockets but no S6 sockets due to failure. (N5 sockets can be repaired sometimes by replacing the innards if you can find a repairer who does this). So whilst its a costlier option I would strongly recommend getting S6 cables from Seacam if you can possibly afford to due to their reliability (caveat - yes I'm biased because I do sell Seacam gear but this is a genuine observation based on my own personal experience - I use S6 and I simply would not go back to N5). I do appreciate that S6 cables from Seacam are expensive but I have found them very reliable and because of their construction they can even be rebuilt or their connectors reused should different cables be needed at a later date.
  9. Optics really isn't hit and miss. There are good reasons why some lenses work better than others behind a port but there are a lot of variables too. The problem is probably that some 'flawed' lenses probably have obvious flaws and not so obvious ones like the production of a curved image field which paradoxically, can help when imaging a curved virtual image. My point being that you can't negate the obvious flaws. Back in the distant past when diopters were fitted to wide angle lenses behind dome ports it was said that the cheaper diopters with one convex and one flat surface were the better ones to use because they induced curvature into the image - but they still weren't very good diopters. This is my take on modern wide angles and their optics. Many high quality modern wide angle lenses incorporate 'close rage correction' (CRC) mechanisms which serve to increase image 'quality' as the lens focusses closer and part of this probably results in a flatter image field. Hence why an older lens without CRC may exhibit better apparent image quality underwater behind a dome. But it will still be an older and less well corrected lens so will limit image 'quality'. To predict image quality behind a dome it would be useful to work a testing system which checks the flatness of image field at the focus settings used behind a dome Perhaps instead of trying to develop better underwater optics we ought to try to figure a way of creating more curvature in the image field for lenses fitted behind domes? Disabling the CRC if possible might help.
  10. To an extent I would disagree with this Adam. I think that topside performance combined with relevant technical data can indicate whether or not a lens may perform well underwater. In my experience mediocre lenses never do perform better as a result of being used underwater.
  11. Almost commonplace? I still haven't seen one in use. And nobody has asked me to supply one. You must be using 'almost' in a different way than I am .
  12. I decided that downsizing a travel housing had become almost essential (caveat - I still have a dSLR housing in case its essential) so I looked at my options. Basically I ended up going from a pro-dSLR (EOS1DS MkIII) to a Sony A7II. The weight reduction for (aluminium) housing and camera body was 5.5Kg to 2.2Kg. So I can now carry most of my kit as hand luggage. However downsizing comes at a price. The A7 is IMO not as easy to use as a dSLR, and consequently has taken some time to get sorted to nearer my liking (and the Sony menu is not a great asset to their cameras). The upside is that image quality is great when it is working as I want it to. Even now I'm still trying to figure optimum lens options - lenses are light(ish) but still limited from Sony. And one housing can take three models. There are other options but I still like full-frame so this is my take on downsizing.
  13. You might also try www.thorlabs.com who produce opto-mechanical parts which can be used to build stuff - using 1/4" x 20tpi which fits tripod threads, or M6 - some of their parts could be used if you like mechano! I use them for all sorts of things - they manufacture in stainless steel and anodised aluminium. As an example: https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=223 Not cheap but probably cheaper than getting stuff machined unless you diy.
  14. Its tricky because the design ethos of the 60EFS and the old 50 macro is quite different. The 50 macro works well on extension tubes at reasonable magnifications whilst the 60EFS is already soft on the 25mm tube. The optical design is quite different with different characteristics. So whilst the 50 certainly should be updated, the newer design of the 60 makes it easier and faster to autofocus and it does so without the lens changing length. My guess is that the 50 macro could all too easily be discontinued without a similar replacement because it represents 'old' technology. Which will be a pity because the new design of macro lenses does not lend itself to increased magnification well with extension tubes. Perhaps I should add that there is hope. Sony's 50/2.8 FE macro recently released is of the older style design so perhaps Canon might just do something?
  15. The Canon 60mm EFS macro will work on a Canon FF body if used with the 12mm MkII Extension tube. It will allow for focus up to about 40cm which may be a little tight for your needs. The Canon 50 macro is a good little lens too and despite its slower mechanical focus, works very well in many situations (how did we work with such lenses on film?). The 50 macro is optically good and myself and my wife have both used it successfully on subjects such as jellyfish in temperate waters which are somewhat murky. Either may work for you, and my only reservation on the 100 macro is that it can sometimes be fussy and hunt a little in my experience.
×
×
  • Create New...