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Everything posted by Interceptor121

  1. The german says conversion kit for the A7RV housing to use the A7IV not viceversa. likely a typo missing an R in the IV
  2. I have the Nikkor uw15 and I have tested it with my A1 it is a very interesting lens for video For photos not so much. The field of view is only 94 degrees and the lens has a working distance underwater of 0.3 meters. With such limited field of view this lens is in today terms unsuitable for cfwa Obviously back in the days when this was the only option the nikkor was great but today no longer It remains a very good choice when you need straight lines although in my opinion the claim that is sharper than other lenses behind a dome at 20mm wildly exaggerated. The benefit is that it is small but for this reason it makes your rig very negative Going back to your calculations you can see from the sony page that the 11mm being a prime doesn’t have the same construction of the 10-20mm Th entrance pupil seems to be 1.5 to 2 cm from the front or 3.5 to 4 from the mount Either way the 140mm will not contain the lens working distance resulting in the lens not being able to focus right on the dome but more importantly extremely unlikely to maintain edge sharpness The fact is there are no rectilinear lenses that are wide enough and do wonders in cfwa. The tamron 17-28mm is the one that comes the closest the sony 11mm with the same 180 port will no doubt perform even better yet a port of such size is an hindrance for close up work I would be genuinely interested in learning of a rectilinear lens able to focus very close and built in a way a large dome is not required the sony 11mm isn’t that lens and the nikkor well it doesn’t even focus close! As of now you have not proposed any rectilinear lens with those features let alone having used one to actually prove the point As such I would say the statement that as of today rectilinear lenses underwater are not suited to close focus wide angle work behind a dome port is correct If such lens exists I am pretty sure I will find it before you do as I am always on the lookout Sent from my iPhone using Tapatalk
  3. That’s right Where is the list of rectilinear lenses that perform very well for close focus wide angle? If there was one I would like to know myself. Yet looking around I have not found one Sent from my iPhone using Tapatalk
  4. So according to you it is fine that I just take that someone who provides no facts or evidence is 'correcting my errors'? I provided a fact based demonstration for the benefit of anyone reading there are plenty of people that can work with the equipment they have but they know themselves they know little about the physics behind To say you are wrong to anyone without providing any evidence is arrogant and clueless which is more than rude and needs correcting
  5. He has no idea otherwise he would have not made this statement Despite over 50 years of experience in UW photography, I have no idea what you are talking about and have spent enough time (politely) correcting your errors. There are not errors in my calculations but there are in his. Besides none of his post amount to 'correction' Example I meant to add some EP figures. Here they are in brackets, as measured from the lens flange: Zeiss 12 (45) Sony Zeiss 24 (40) Sony 10-20 (45) Samyang 12 (38) If the Sony 11 is similar to the 10-20 then the distance from the sensor to the EP will be 63mm (not 53mm), using a figure of 18mm for the distance from sensor to lens flange. 1. Where did he get his entrance pupil from? 2. A lens that is wider than other will not have the same position of the entrance pupil 3. The data of the 10-20 looks very wrong as the lens is 55mm so the lens entrance pupil is definitely not going to be just 1 cm from the front 4. Even if the data was correct 150-63=87mm which is larger than 69mm hence the lens will not focus on the surface of the 140mm dome suggested Indeed looking at the patent of the 10-18mm the entrance pupil is around 15mm from the front and this lens is a very similar construction to the 11mm and it is wider so safer to assume it is further back then 1 cm suggested, more than 1.5 and more likely 2 cm Which just puts the radius closer to the 9.7 cm I indicated Now I would like to know where were the errors in what I wrote and how the guess work of that person is a fact able to correct an error and more importantly how that makes a big difference considering the lens still does not focus on the dome If he had an idea he would have put some facts and test data instead of probing a real test case that I provided in the thread with unsubstantiated theory that has no legs to stand on My statement that the person 'correcting errors' had a problem with is this one the discussion seems to continue on this comparison between a water contact optic and a rectilinear lens however rectilinear lenses are NOT good for close shots No evidence has been provided to the contrary not a single rectilinear wide angle lens has been listed here capable of very close focusing behind a dome port If anyone has some examples I would like to see them otherwise the 'generalisation' is appropriate
  6. I am not an English native speaker but I write a lot of reports that undergo formal scrutiny The statement I made was perfectly accurate and appropriate It said Sometimes experience does not mean technical competence According to the oxford English dictionary I have here sometimes means occasionally but not all the time From here I would conclude that your statement that i was condescending is flawed If I had said most times or usually it would have been different It is unusual that you choose to belong to the occasional rather than common members of the audience Either you decided to have a go at me or you chose to read the sentence differently because you may know the person who that was addresses to it doesn’t matter In this case you just didn’t read the sentence correctly PS my writings are correct while your statements are just made out of convenience other times you were ready to jump on my throat to say that larger dome is better while this time you suggest not? And exactly why other than having a go at me? Again the op has tested nothing this is based on his own data and that alone your statements add little no nothing to the discussion and seem rather biased and personal and free of any fact nor adding any clarity to the issue at hand Perhaps you are able to comment on why a rectiliner lens is instead ideal for close focus wide angle and articulate your findings? Sent from my iPhone using Tapatalk
  7. The comment wasn’t for you strange that you feel that way you put yourself in the less technically savvy? Why exactly? The person referred to errors there are none except in his mind What follows are working why what I say is correct and not wrong and in any case closer to the truth It’s funny that someone can come with a whole load of numbers which still make no sense one corrects it and gets detractors coming in Nobody goes there and tries to fix the error in the first place though Again it’s not rocket science you can’t say it is complex when convenient and simple when it suits you Things are what they are what changes is the observer. Someone can’t get anything at all of the same dataset and another gets insight Sent from my iPhone using Tapatalk
  8. The comment wasn’t for you strange that you feel that way you put yourself in the less technically savvy? Why exactly? The person referred to errors there are none except in his mind What follows are working why what I say is correct and not wrong and in any case closer to the truth It’s funny that someone can come with a whole load of numbers which still make no sense one corrects it and gets detractors coming in Nobody goes there and tries to fix the error in the first place though Again it’s not rocket science you can’t say it is complex when convenient and simple when it suits you Things are what they are what changes is the observer. Someone can’t get anything at all of the same dataset and another gets insight Sent from my iPhone using Tapatalk
  9. https://www.nauticam.com/products/na-a7rv-housing-for-sony-α7r-v-camera Compatible cameras: Sony α7R V camera, α7R IV with Conversion Kit I believe conversion kit means a different tray and adapters So if you buy the R5 housing you can use R4 and R5 viceversa normally not supported
  10. Sometimes experience does not mean technical competence There are plenty of experienced photographers that do not have any idea of how the device they use and produce great photos actually works I will try to make an effort so your understanding improves but I believe this may fail In order to focus a lens to the minimum working distance you need to calculate the radius of a dome that will have the surface exactly in that point which is calculated from the sensor. The Sony 11mm 1.8 has a minimum working distance of 15 cm and the lens is 5.5 cm long. Even not having any entrance pupil measurements from the filter size and the build of the lens you can see that the entrance pupil will be around 20mm from the front of the lens. It cannot be at 45mm from the sensor as you indicated because it would vignette with the 55mm filter thread. This gives us 55-30=35mm from the mount or 35+18=53mm from the sensor plane. MOD = 150mm subtract 53mm gives 97mm Minimum radius to focus on the dome 9.7 cm lens will focus on the dome Now change the situation and use a 140mm dome that has a radius of 69mm you are 28mm short the lens will not focus right on the dome but because you are in water it will now be 5 cm away in total 53+69+50=173mm from the sensor At the end your 140mm dome will actually focus further away than the lens working distance because it is too small Any lens will eventually work with a dome smaller than the ideal one however this means the lens will no longer focus that close and the image will look blurry Now if you wanted to get really close you consider the Tokina 10-17mm that has a working distance of 14 cm the entrance pupil is very close to the edge and the flange distance is 44mm requiring a very small radius You can use this lens with a 100mm or 110mm minidome and be right on top of things and have decent image quality with your Sony APSC camera. The lens also zooms so if you want you can make things look bigger Hence the Tokina 10-17mm really is the best option for the APSC user regardless of format for CFWA And of course generally CFWA <> rectilinear lens underwater not matter which format you use as of today
  11. The adapter is irrelevant to the calculation of the minimum radius The extension calculation are only important for the position In order to focus at 15cm you need 9.7 cm radius this is based purely on how the lens is built The lens is 55mm the entrance pupil is inside the lens not outside even your assumption of 45mm brings 8.7 which is still bigger than 69mm of the 140mm dome. So you still need the 180mm dome to focus right at 15cm The best option for cfwa on sony apsc is to adapt a tokina 10-17mm Sent from my iPhone using Tapatalk
  12. I looked at the 11mm myself for other reasons The working distance is 15 cm however the lens itself is very small Likely position of entrance pupil 2cm from the front so 5.3 cm from sensor 15-5.3= 9.7 cm radius required 140mm dome too small As I said lenses that focus close but are themselves very small are not well designed for performance behind a dome The 11mm will work with the 180mm dome The canon 8-15mm focuses at 15 cm but the entrance pupil is 10.8 from the sensor making the minimum radius required only 4.2 cm Short working distance and small lens is not a good combination Sent from my iPhone using Tapatalk
  13. I do not think the sigma is not a better choice because it extends more than the tamron so it will have less zoom range available and in addition is not a great lens on its own especially on the edges The tamron 28-75mm G2 with WACP-1 should be able to do 28-50mm however with the lens back from the glass I am unsure about the image quality Generally it looks like big format 28-70 or 28-75 lenses are not a good fit for the WACP-C but wider lens zoomed work well judhing from the results of the 17-28mm that does not vignette at 26mm. It must have to do with the lens design and where the entrance pupil is located
  14. Update on the 28-75mm G2 today I got the adapter ring I was after and unfortunately the lens vignettes at 28mm just a bit but you can see it therefore this lens is more for the WACP-1 someone else will have to check if that works
  15. Practically though this is not a possibility as most rectilinear lenses focus at best at 20cm I have a lens that focuses at 19 cm and requires a dome with a radius of 11cm The whole rig is around 16.5 long and 20 cm wide at the port which is bulky The smallest frame you can capture is 40 cm wide The fisheye lens at 15cm will have a frame that is 98 cm which is much wider The dome will be small making you better able to get close Hence cfwa means fisheye lens not rectilinear lens Even if you work on crop sensors (i have an MFT camera) things don’t change It is just the physics of it and the facts are specific not generic Sent from my iPhone using Tapatalk
  16. That didn’t mean what you implied at all! Sent from my iPhone using Tapatalk
  17. Nobody framed any rules By definition tor cfwa you need wide field of view and this is best accomplished by fisheye optics If you go with a rectilinear lens you are back at perspective issues and big domes do not allow you to get close You go small your rectilinear lens will not focus Sent from my iPhone using Tapatalk
  18. Sorry I am not quite sure what you commented on to be frank now This is not about photographic techique which is subjective is about physics A rectilinear lens is almost free of perspective distortion at 24mm it is totally free at 35mm The field of view of a 35mm lens is such that at 1 meter the frame is 1 meter wide It follow that if your frame is 2 meters you need to be at 2 meters however you can also have a wider lens of 18mm and now you are back at 1 meter Or you could be at 0.67m with a 12mm lens As you move to wider lenses and get closer for the same frame size you have an issue of perspective distortion eventually if you need to get even closer if you want to avoid the suspended particles in low visibility so here you need some fisheye like optics that will have barrell distortion a form of exaggerate perspective distortion In terms of shooting a 2m shark in poor visibility at 2 meter with oblique framing you are still at 1.65 meters and all the suspended particles will make a strobe shot impossible What follows is opinion 35mm is the standard wide shot on land for filming however underwater this does not apply as there is water in the middle generally I would say a multiplier of 0.5x applies so whatever you shot at 35mm is now more or less 18mm I use all sorts of optics and it is important to understand what a certain lens can or not accomplish when you have constraints imposed by the water medium. If someone wants to go ahead and shot a 12mm lens close, something even topside you would not do but may be required underwater to get the lights on the subject, of course go ahead and see if you like it. I don't and the dome optics do not help that use case degrading the image quality further
  19. The M5 ball arm is $28 I paid £24 in UK. This is by far the cheapest neatest option
  20. It is not an odd comment Getting close is essential to preserve colours in underwater photography. If you have a lens with a narrow field of view and your subject is not small (wide angle) you will need to step back further away which in turn means more water between you and the subject and this is where problems arise If your subject is 2 meters with your 35mm lens you need to be 2 meters away this is going to lead to issue. If your subject is 20 cm then this is a different story but then you don't talk about wide angle those are just close up shots
  21. No it is not just like that If you use a smaller radius than needed the lens focuses away from the dome but the infinity point doesn’t change So your too small dome eats away the focus range eating away the image quality Better to get a lens that fits better in the 180mm dome if that is what you want The tamron 17-28 and Sony 24-70GM2 work well the latter doesn’t need 55mm extension in my view 50mm is sufficient and the 250mm port is not required Sent from my iPhone using Tapatalk
  22. I have not written the 28-75mm G2 off however I am having trouble fitting it. This lens is built in a way that WACP-1 may be a better fit Tamron 20-40mm is next on the list am trying to organise a zoom gear Sent from my iPhone using Tapatalk
  23. In order to pick up a wide angle port you need two ingredients 1. The right field of view. 2. The appropriate radius This lens has a narrow field of view so any of the 3 Nauticam glass wide angle port will work The lens construction however is such that a large radius is required so the performance will be sensibily better with the 250mm wide angle port. Then the 230 and 180 in order. With the 180mm port the lens will not focus on the dome and performance will be affected It is one of those cases where a lens is not built for ideal underwater use
  24. The 17-28mm was a fall back plan I think the 28-75G2 will not work equally well at least with this lens may be better with the larger WACP-1 The intention is to get a lens that works in the 28-40mm range which is more or less 130-90 degrees Longer frankly is not really needed I have looked at all my WWL-1 shots they are all 14-20 which is corresponding to this Surprisingly the lens worked at 26mm not sure the production lens will This is experiment phase I there is II and III planned and they are zooms Sent from my iPhone using Tapatalk
  25. Thanks to @Alex_Mustard I have started my testing of the WACP-C prototype aka WWL1-DRY The first lens to go through is the tamron 17-28mm that did not vignette at 26mm despite my extension was 5mm too long. Image quality is far superior to the Sony 28-60mm already like this and will get better with a shorter extension https://interceptor121.com/2023/04/07/wacp-prototype-experiments/ For you pixel peeper here is a field of curvature test shot at f/5.6
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