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Everything posted by Interceptor121

  1. I agree. The principle however needs to be apples with apples. My opinion is that the 4.33” acrylic is the best for compact set up. Either apsc or mft with metabones the second having more depth of field with tokina Having a compact rig comes with compromises and I am trying all combinations in the pool before going to the ocean Sent from my iPhone using Tapatalk
  2. I thought that if you push the lens in the dome you get barrel distortion so the image looks even more bent I have studied all nauticam glass ports there is a summary pdf For rectilinear lenses with a working distance of 28cm even the 230mm dome is not big enough after all the radius is 12cm. The 180 dome that is more compact has a radius of 11cm however only supports a smaller angle of view For CFWA the smallest nauticam port that is still a full dome is the 4.33” If you are interested in getting closer and you have one of tokina 10-17 nikon or canon 8-15mm this is the lightest more compact and least expensive port for CFWA It has also an added benefit that is much more positive this is especially valuable if you have a mirrorless camera and wanted to have a compact rig. The smaller zen dp100 will get you even closer but it is negative and more expensive and it’s glass For cfwa where the risk of scratches is higher i believe acrylic is a good choice Emwl etc are not something I have looked at and i am still unclear on how to model some of the water compact optics Sent from my iPhone using Tapatalk
  3. Thanks for the link to the article The Sigma 15mm has a specific design. The lens is smaller than other fisheye from Canon or Nikon 8-15mm but the working distance is the same. Here is a link to the lens design https://photonstophotos.net/GeneralTopics/Lenses/OpticalBench/OpticalBench.htm#Data/JP1990-248910_Example01P.txt Note how the PD is set 16.34mm from the front of the lens while the distance from the image plane is I-P=78.89mm Considering a working distance of 150mm and taking out I-P results in 71.11mm This means the dome inner radius must be at least 71.11 otherwise the lens won't be able to focus right on the dome when housed. Nauticam 140mm dome whose radius is 69mm just falls short of this specifications. In addition a smaller dome like Zen DP100 (100mm on the outside but 94mm on the inside) will not work well with this lens which will still not be able to focus as close as required. The smaller dome will only result in less useable working range for the lens. Definitely not a good combination for this lens. I would also add not a good choice of minidome for the Nikon 16mm Canon 16mm fisheye all lenses that do not focus close enough to work well with small domes and really requires larger ports. However the Canon 8-15mm or the Nikon 8-15mm are much larger lenses with the same working distance from the image plane of the Sigma 15mm also more expensive if I can add. Looking at the canon and doing the same calculations of the sigma results in a minumum radius of just 39.55mm to focus right on the glass. I would therefore conclude that users of those 8-15mm lenses (nikon is pretty much the same) can actually use a very small dome and the camera when house will focus right on it. I am not suggesting this is the right thing to do however if you wanted to get very close you can do it with those lenses. In terms of depth of field you need to take into accoun that the focus distance is taken from the image plane not from the centre of the dome. So if you consider the same example of the Canon 8-15mm you need to add 108mm to the virtual image plus the space inside the dome Assuming Nauticam 140mm dome this is 108+69+(69*3)=384mm infinity If you take a dome with a radius of 12cm (similar to the nauticam 230 wide angle port) this is 108+120+(120*3)=588mm infinity None of those ports will have enough depth of field at f/22 to reach the infinity point when the target is touching the dome Now some other theoretical calculations Imagine a target at half meter with a 6" dome this will be around 12.5 cm from the dome surface however this means 30cm from the focal plane. At f/8 this already covers 0.43m which is larger than the infinity point The same target at half meter with a 10" dome is actually 18cm from the surface however this means 40cm from the focal plane with the infinity point at 58cm. I can cover that range at f/6.3 As the target moves further away the requirements on depth of field drop. So the larger dome results in a 2/3 stops increase in depth of field for a 1.66x size increase. Looking at weight for reference to the nauticam 140mm fisheye dome and the 230mm wide angle port the weight is double Obviously if you are interested in the sharpness front to bottom larger is better and if your lens does not focus that close larger is mandatory Generally all the calculations I am running under the assumption the dome is properly placed at the entrance pupil show that on fisheye lenses improvement in depth of field in stops is pretty much log2(radius1/radius2). So a dome with 11cm radius will have 2/3 stops over one of 7cm radius. And the difference between 4.33" and 5 1/2" is 1/3 BUT you need to make sure your lens can focus. The Canon/Nikon 8-15mm will work with any size you like ultimately it becomes a compromise between size/cost/quality I am still puzzled by the 230mm wide angle port being called at times a fisheye dome when it does not cover 180 degrees but that is another story
  4. As owner of the 140mm I would say this dome is not that compact. The weight on land is 1.3kg and the housing becomes very negative when you use it. I have recently acquired a float belt as together with the evf there was no way to make the rig neutral no matter the number of floats on the arm I think the 4.33" acrylic solution is actually a very good option as it makes the rig less negative. Even the DP100 from Zen is very negative due to the not small weight and reduced buoyancy In hindsight (net of reflection) I should have got the 4.33" acrylic dome for my GH5 but it was not specified on the nauticam chart however I have been assured it is fully compatible with the canon 8-15 as it is with the nikon 8-15mm and of course the tokina 10-17mm I would like to find that article from @Alex_Mustard because on a recent piece from Matty Smith there are comparative photos of domes for the purpose of split shot and while it is fully understood why a huge dome is important for the topside part of a split shot I cannot see any strong evidence of better performance in the underwater part
  5. This is the original article https://www.retra-uwt.com/blogs/news/comparing-light-ouput When you look at the image with the tests without diffusers you see that the new retra flash is much wider than the original However when you look at the shot with diffuser the new flash due to the design benefits less than the diffuser and the gap is not so large The measurements that follow are without diffuser which is not how you would use a strobe with linear tubes including the z330 There is a useful table of physical dimensions and weights There is no doubt that retra products are well built by someone who knows their stuff very well
  6. This home made diagram shows how the field of curvature in an underwater dome (left) differs from the classic lens field of curvature (right) classic case when the focus point is the same the larger lens is less bent and therefore suffers less from field of curvature However underwater due to virtual image the focus point is not in the same position. Is like two concentric circles and infinity is around 4x the radius. As the circle gets bigger for the same field of view the distance from the top of the circumference is larger as the circle grows larger. In addition the chord align to the focus point gets wider and field of curvature grows as you deviate from centre I still think that a larger lens may be better but this is not at all the same situation of a lens topside as there is no virtual image there I have just written in to some guys that look at telescope optics (this is an issue in long lens astrophotography) to ask what they think about domes.
  7. 1. A good monitor that is at least 100% sRGB better if it has DisplayP3 and/or AdobeRGB though the latter is going in disuse 2. Unless you use noise reduction software or some CPU intensive software like stacking and process hundred of images you will find many computers digest photos just fine If you are in the apple universe the new mac mini with a good screen works very well. You can use SSD if you have libraries with many images however I only do that on my laptop and store my library on a professional grade hard drive. I cannot stress how important is a good screen but also to keep it calibrated
  8. I still have my two Sea and Sea YS-D2. It has been a few years I am sure eventually they will fail but I like the light they produce very much. In Italy I have seen a few OneUW I have to say they look impressive if not a bit bulky. The quality of light seems very good Retra Pro X area also very popular light quality seems very good too but to be honest so are seacam that are very similar to OneUW The thing with the Japanese strobes at the bottom of your table is that they are substantially lighter of the other strobes I am not a fan of the dome shape of the Z330 though and I do not see the YS-D3 as a step forward the light looks cooler so I would not consider those last two
  9. I have found a very detailed source in optics however it doesn’t model underwater scenarios Interestingly there is a formula where you can see the role of physical aperture distance from the centre radius of curvature This shows that the focus error increases as you go on the edges and decreases as the entrance pupil size goes down so that explains why closing the aperture helps However I am not clear about the gaussian focus point and the radius of curvature calculation and how they are impacted by the dome Sent from my iPhone using Tapatalk
  10. The virtual image lies in a different circle so the curvature is the same for the same angle of view You can draw two concentric circles with two different radius and draw the same angle of view The distance between the chord and and the circumference is larger for a larger circle so this defeats the increased depth of field What matters is the angle of view. If you have a super wide lens no matter the size of the dome the distance edge ve chord increases to the point you run out of depth of field In practical terms you choose a dome based on the lens ability to focus that pretty much sets the radius and the angle of view of the lens You can’t choose too small radius otherwise the lens focuses too far away from the glass But it you make it too large you get too far away from your subjects It is generally not a good idea having a too wide rectilinear lens. No matter the size of the dome the angle of view makes the edges blurry and if you close the aperture you get to a point where the centre is no longer sharp due to diffraction I never go wider than 16mm which for me is the absolute limit Sent from my iPhone using Tapatalk
  11. Not the lens whose field of curvature is corrected The dome has field of curvature that is not corrected For a given angle the field of curvature is the distance of the arc from the circumference which grows with the radius Closing the aperture reduces the effect of field of curvature but as larger radius has more this compensates for the larger depth of field The most important factor is the field of view wider it is more blur at the edges Sent from my iPhone using Tapatalk
  12. Actually not at all Dome are affected by field of curvature it is much simpler than I thought And field of curvature is worst as the radius grows The radius of a dome is mostly driven by the lens working distance and the position of the entrance pupil relative to the lens body and size Look up petzval field of curvature The primary driver of blurred edges is the angle of view as that aggravates the perzval effect A case of common misconception really Depth of field is unrelated but closing down the aperture limits the issue Lens are corrected for field of curvature but adding a dome introduces the issue to a larger extent Sent from my iPhone using Tapatalk
  13. I have read those. No reference or evidence whatsoever between dome size and edge sharpness Dome size and working distance are related, however edges relate to field of curvature normally
  14. Yet this doesn’t relate to edge sharpness which might relate to field of curvature As I said no actual model to correlate the two Sent from my iPhone using Tapatalk
  15. I have been doing some research on fisheye lenses, domes etc and I do not see a single source to suggest that large domes improve corner sharpness The original articles from reefnet scubageek show a correlation between lens working distance (from the lens entrance pupil) and dome radius The whole argument is that the radius of the dome needs to be large enough for the lens to be able to focus There are other articles showing that if a lens does not focus close enough you can introduce a diopter to improve matters and that the diopter introduces a loss of depth of field as it should be but I see no reference to edge sharpness When I look at sea and sea lens corrector this is a field flattener as used in some telescopes this is used to correct field of curvature and/or coma but introduces astigmastism this is the closest I have seen to address the edges issue In addition fisheye lenses are distorted and therefore by definition aggravate the issue of field of curvature Can someone point me to a scientific explanation of why using the same lens but different size domes I should achieve better corner sharpness? I am interested in a theoretical model not to real life tests in non repeatable conditions like oceans etc. Thank you
  16. The 60mm is a lens that wasn’t doing particularly well stopped down If you look at dpreview sample gallery all the shots are at f/10 or below which is under diffraction limit Lets see if there is a special port for underwater but this is going to be a niche product Sent from my iPhone using Tapatalk
  17. There is a complex situation with digital cameras with small pixels Diffraction limits the MFT sensor from f/11 however resolution drop starts earlier Generally at current megapixel count lenses peak between f/2.8 and f/5.6 depending on how wide the lens goes At f/16 looking at lenstip charts you have around 1.4 megapixels resolution which is really low You also have to consider that topside you can use in some use cases focus stacking shooting at peak resolution Ultimately I personally think a shorter lens and a wet lens is more suited to underwater use costs less and is more flexible Sent from my iPhone using Tapatalk
  18. Excellent it confirms my theoretical model see post on blackwater diving The 85mm has limited focus breathing so it should work well and so should the 40mm if you like that focal length It is a newer lens so should work better than the 60mm which is now discontinued It looks like IT IS possible to foresee lenses behaviour underwater just looking at the design if you know what you are looking for.
  19. the idea of CFWA is to get close so you want the smallest possible dome that still allows the camera to focus and preserve the field of view The panasonic 8mm and the 4.33 acrylic dome offer this ability. The only challenge is occasional reflections in the dome which requires you to mask the writing on the lens and may still come around The larger dome has a radius of 1.4 cm more the main benefit is not the larger size as you will be further away but the optical glass with antireflective coating that is useful if you want to shoot backlit shots and sunbursts Other than those shooting situations you will not see any visible difference
  20. Normally a lens achieves the best performance a few stops down from wide open However MFT already starts to suffer at f/8 so this means this lens will not be as sharp as others Looking at their tests they are correct the lens stops at 70 lpmm which is not a lot considering the maximum at sensor level is 150 lpmm At the end you need depth of field so this will drop further down Sent from my iPhone using Tapatalk
  21. The point is that at f/3.5 the lens is limited and overall the level of sharpness that comes out is not amazing There are some limitations of the sensor size when you go past f/10 so I think the point of lenstip is that this is not a very sharp lens however there is no other lens like this so the question is more how does it compare to non native lenses or to using close up lenses
  22. No the lens is still 90mm 3.5 a lens is what it is
  23. Less favourable from lenstip https://www.lenstip.com/644.1-Lens_review-OM_System_M.Zuiko_Digital_ED_90_mm_f_3.5_Macro_IS_PRO.htm I do agree they could have made the lens a bit faster MFT starts to be diffraction limited at f/11 this is an issue of the format however you rather take depth of field than blur
  24. So Nikkor AF-S Mirco Nikkor 60mm 2.8 EGD - Full Frame - DISCONTINUED which was on my list works. I think is the lens that is making the difference not the camera I would like to hear from other users about the other lenses
  25. Interesting lens. It will require a long flat port. 135 - 25 = 115 mm 65 flat port plus 20mm extension plus 30mm extension Not sure about the flexibility of this set up compared to a 60mm plus cmc-1 for sure the optical quality will be better as the 60mm at f/11 is not great
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