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Hi all, I'm looking for a 140 mm glass dome port which I can use with my Isotta housing, and due to another post in this forum I have discover this HowShot dome ports which I didn't know. If anyone can give me information about the quality it would be great. After upgrading to the Canon R6 mkII camera in Isotta housing I found out that the corners in the pictures with the 4" dome port are blurry, so I have to purchase a 6" dome port. The options are Nauticam 140mm glass dome port, which are really expensive when I finally adapt it to my Isotta, I also can purchase Sea&Sea and Isotta 6" dome ports but this ones are plastic, and in these brands the glass domes are 6,5" which are to big for CFWA. So this HowShot looks great in size and price, but I don't know anything about them.

Really good idea to shoot a mono-colour wall and see what you can see. As @Architeuthis says, same as a dust spot test shot.

As the others say - it may be condensation, especially the last two photos... I am not sure that the black shadows is condensation as well, maybe it is condensation at the end of the lens or on one or both ends of the TC. Hopefully it is not the sensor (it may be a sensor on the way to die (e.g. moisture inside the layers). One should have a close look at all the components with a loupe (especially at the sensor with a special "sensor loupe" with LED lights, if you have one)... You could also make a test, in order to se whether there are any remains still there (but too faint to be detectable in regular photos) and to locate the source: first entire configuration (camera/TC/Canon8-15mm). Make focused (also defocused) photos of a homogeneous white wall. Then overprocess in LR (unnaturally high contrast/clarity/defogging) to see whether there are any remains of the shadows visible (similar to testing the sensor for dust speckles). In case you see some remains, first remove TC and repeat. When still there try another lens. When it shows up also with another lens, it is, unfortunately the sensor...

For me like the other... condensation I allways try to close the housing in a an air conditioned space... (if it is possible)

Check the o-ring is clean and seating properly, lubing it wouldn't hurt either. A couple of minutes seems faster than what I would expect for just a bit of grit or hair on an o-ring. If that doesn't help, pack the housing with tissue paper, add a weight and submerge it empty (no camera) for a couple of minutes to see where water gets in based on where the tissue gets wet.

It's not a native Sony lens but the Laowa 10mm dome was tested and discussed extensively including using it in a 140mm dome some time back, here's a thread mainly testing Canon lenses and some of them including the 10mm laowa in the 140mm dome. This was tested as Canon mount MF lens but they make it in a Sony mount in AF. In the absence of any experience on Sony native rectilinear in the 140mm dome this may give some idea on what you might expect, in general terms 140mm is regarded as too small a dome for most rectilinear lenses and I don't recall seeing much discussion on the topic here. Some more detail on the 10mm laowa here, quite an extensive thread: Scrolling down is some information on Sony lenses that work well in the 180mm dome. The Laowa seems to be a special case working as well as it dies in the 140mm dome, it is generally thought that the very short minimum focus distance helps the lens perform better than other rectilinear lenses. Without doubt the best performer in a 140mm dome is going to be the Canon 8-15. Fisheyes play better with dome ports and can work very well in quite small ports.

@Chris Ross it's pretty quick. Less than a couple minutes. yes it's the push button valve. I'll remove it and try again.

Might have been condensation on the rear element of the fisheye lens of the front element of the 2x. Particularly the last frame looks foggy like condensation. This could happen if the camera/lens was cold and had come out of an air conditioned area. The housing would warm up in the air as would the dome, but the 8-15 is a heavy lump of glass and could have stayed cold (high thermal mass). As it slowly warmed up the condensation re-evaporated. Opening up on the boat could have let very humid air in, more humid than back on land. Sealing in an air conditioned space is good, but if you open the housing you let humid air in and it will find the coldest thing to condense on. Ideally have your camera outside at ambient temperature and bring it inside to seal it up.

If you ruled out the port getting fogged i would be looking at the lens. Loose the TC to remove another variable. Are you able to seal the camera in an air conditioned space?

The RC protocol sends optical signals to the strobe to tell it how long to fire for so the camera can actually communicate to the strobe during the exposure. The exposure is set purely on the pre-flash image in both protocols. In theory the sTTL should do the same job as it is trying to mimic the durations of the pre-flash and the calculated main flash length, but in practice it seems it doesn't necessarily work that way. Another point is that RC mode tells the strobe to emit a pre-flash, which the camera reads. The pre-flash power is known by the strobe and all the camera needs to do is to send a multiplier for the pre-flash duration to get the exposure right, so if for example if the pre-flash power is 1/32 and you needs 4 stops more power in the main exposure the strobe needs to fire at 1/32 x 2 x2 x2 x2 = 1/2 power . In standard TTL there are assumptions about how powerful the pre-flash is as a percentage of the strobes full power as the camera has no idea about how much power the UW strobe actually has.. There are also issues with measuring the power of the pre-flash in the UW strobe as the duration may not be in the optimum range for triggering the UW strobe and it may not match the duration of the trigger signal from the camera. An RC UW strobe though knows exactly what power the pre-flash was it can then can do the calculations based on the communication signals from the camera to work out how long (how much power) the strobe needs to fire for in the main exposure.

I’m wondering if it was condensation on the sensor through that opening if the housing? Pretty difficult to remove in LR. You could try using the Brush with a slightly negative EV.

And whilst I'm not hopeful, is there any way to remove this in Lightroom or any other app?

Hi all On my recent dives in Triton Bay, I experienced something I've never seen before, and I can't figure out the cause. Set up is Sony A7R5 in Nauticam housing with Canon 8-15mm fisheye, Sony 2x teleconverter, Metabones V, behind Nauticam 140mm glass dome. The best way I can describe what happened was the lens was perfectly fine as I got in the water, then after ~5min became what was in the first image (small black shadow), then over the course of the next 10min progressed to what is in the 3rd and 4th image (big black shadow covering the full frame basically). I did not see any visible condensation behind the dome. I had to open up the housing on the boat as my vacuum flashed yellow on the ride over to the dive site, turned out to be some sand on the o-ring which was cleaned, and vacuum stayed green as this happened / no leak. I went up mid dive to open the housing again, and as I checked through the viewfinder, it was clear. I went back down and did not experience this again on the rest of the dive, nor through the second dive. However, after looking through my photos in detail, I noticed I had the mild black shadow yesterday as well on some shots, akin to photo 1, but I did not notice and it went away after a few shots (i.e. 95% of the dive was fine) I cannot figure out what this is. If it's condensation surely I would be able to see it? Has anyone experienced this? tx

Nauticam's port chart is extremely limited on the use of the 140mm dome for Sony n100 a7s/r full frame series. Has anyone had any experience with native Sony lenses using the 140mm dome that they can provide first-hand commentary on. No speculation please, just actual experience. TIA

I don't see how the standard lens correction tools in photoshop can do what you are saying, maybe lightroom has a different tool to capture one which I use. Before you write it off I would suggest you use the lens correction tool and see what it actually does and you can see how it changes the image shape when it is used. Have a look at about 6:20 mark of this video: You can see the top of the image bows in to correct the barrel distortion and you have to crop the image. If what you say is correct then when zoomed at 24mm and auto-corrected the field of view won't be as wide as a standard well corrected 24mm prime, because the correction tools need to crop to remove the barrel distortion. You would indeed likely get better corners at 28mm when you zoom in and then use the WWL I believe, the digital picture notes that corners improve at 28mm. In theory if you crop an image out of the vignetted image and don't apply distortion corrections, then the image won't be degraded further by those distortion corrections. I'm assuming you don't see those non-illuminated parts of the raw image in the viewfinder. This being the case the camera is cropping the image from the sensor so you can properly frame your image to match what happens after the corrections have been done.

Can someone explain to me why TTL exposure, such as Olympus RC, is better than slave sTTL? I recently stitched from an Inon (sTTL metering) to a Backscatter strobe (Olympus RC metering). While I normally shoot manual I have noticed RC works better than sTTL for the wide-angle work that I do. I would now like to understand: why? Unless I am missing something the process is functionally similar: sTTL: Camera is not aware of external strobe. Camera flash fires a single weak preflash. Strobe attempts to mimic the duration/strength of the pre flash. Camera calculates exposure/required flash duration assuming the more powerful strobes pre-flash came from its own flash. I assume the camera is measuring both pre flash and ambient light, and allowing for metering area (matrix, spot, etc). Camera fires flash for main exposure. Strobe attempts to mimic duration/strength of camera flash. RC/TTL: Camera is aware of external strobe. Strobe fires a weak pre-flash, or more likely, multiple pre-flashes. Camera calculates exposure based on the strobes pre-flash. This likely includes pre-flash and ambient light, and allows for metering area. Camera fires strobe for actual exposure. My understanding is that a mirrorless camera will not stop the flash or strobe when correct exposure is reached on the sensor in step 4 - the flash duration is set during step 3. Correct me if I'm wrong. During my reading on this I see a lot of vague comments such as ‘in TTL the camera talks to the strobe’, 'in TTL the camera is aware of the strobe and is properly metering the scene' or ‘sTTL is only based off pre flash strength’ but no actual concrete answer. So - what am I missing? Why is RC better, or alternatively, do you find both are similar? The only partial answer I’ve seen is that in sTTL the camera is firing blind: it is firing its own flash but seeing the light from the more powerful strobe and assumes it's from its own flash, while the sTTL strobe does not know what camera, flash or lens is being used, and is following a generic ratio/protocol in deciding what output should match the weaker camera flash. This can lead to underexposure in the final image due to the pre flash being too bright. I also assume it may lead to overexposure when the preflash was too weak/the subject too distant, but this would apply to both sTTL and RC. Hopefully someone can come along and explain the key differences between sTTL and RC to me (particularly in wide angle with a bright or dark background) as if I’m 5 years old. :-) Cheers Rohan

How quickly does it lose vacuum? if it's quite slow it will be an o-ring leaking most likely. If it's really quick, it's potentially either the valve was not installed properly - check it o-ring is in position or the new valve is faulty or perhaps you've pinched an o-ring. Is it the push button style vacuum valve?

Unfortunately you most likely have a leak somewhere. Could be any of the buttons ect with an o-ring. You could try to use leak detection smoke to pinpoint where it is, but if its really small, it might be useless. Your local dealer can service and change everything im sure.

If I understand correctly, you would like me to use the original size image, crop a corner and upload the crop sample? I will do what I think you are asking for.

It doesn’t matter Chris, in both exercises the corners massively loose image quality and resolution (sharpness). The lens is 24mm FOV but i lacks corner sharpness as the straightening lens correction digital process degrades IQ massively. You will simply never get high quality sharp corners with that lens and a Nauticam WWL-C as the corners are never recorded on the sensor @ 24mm. Period. The interesting exercise is looking at RAW files that have been shot @28mm or 30mm to learn if combining the RF24-50 STM with WWL-1B or an Marelux Aquista 110 or Aquista 130 is going to be the better solution.

Recently had an issue with my vacuum valve not working so have replaced it. Sadly, it's still not holding a green light so seems the problem was greater than that single issue. I can't see anything obvious so was hoping for some guidance on trouble shooting it to see if i can find the issue and fix it myself. Any ideas?

In fact fisheyes play better with domes, the Canon 8-15 is an amazingly sharp lens and the Tokina 10-17 works better UW than it does on land. This is because of dome port optics where the lens is focusing on a virtual image located around 3 dome radii from the dome surface. The Rectilinear wides are designed to focus on a flat plane. so struggle more and more towards the corners. The focal plane of a fisheye lens is curved around the lens so it matches the shape of the virtual image. I dive temperate waters around Sydney and shoot mostly macro with some use of the 12-40 lens (24-80 equivalent) on offshore dives and also using my 8-15 fisheye there on occasions. I have a 7-14 lens (14-28 equivalent) and it uses the same dome as the 12-40, but I rarely use it. I'm not sure the 10-18 would be a great lens for CFWA. To be really effective this requires the lens to focus on the glass of a small dome. Fisheyes do this, but rectilnears have poor corner performance in small domes. Fisheyes have barrel distortion which enlarges the centre of the field relative to the edges and this has the effect of bring the subject forward with the background seemingly receding and this gives the images more impact. The Tokina 10-17 zooms from 180° diagonal fisheye all the way through to about 23-24mm focal length range, so effectively combines the fisheye with the range of of a lens like the 10-18, it just doesn't quite have the reach, but it's close. The 22-24mm focal length range refers to the width of the frame of a wide angle (rectilinear) lens zoomed to about 24mm or so.

The lens correction is removing barrel distortion and you can demonstrate this on a fisheye image with the lens correction tools in your IP program. Here is an example image taken with a Panasonic 8mm fisheye: If you use the lens correction tool it removes the barrel distortion at the cost of a reduced field of view: You can see that the image has lost the edges and it hasn't even been fully de-fished yet, so it doesn't actually stretch the image into the corners, but crops them out. I expect the lens correction on the 24-50 does something similar and I expect what Canon has done is that the 24-50 is actually wider than the a standard 24mm lens, knowing full well it will lose the corners when the barrel distortion correction is done. Unless you are doing raw conversions in Canons software the correction will be done using Lightroom's standard lens correction tool. It would be an interesting exercise to compare an image cropped out of the raw file with one that is automatically corrected and also to determine if the 24-50 has the same maximum field as a regular 24mm lens.

Thanks for the pictures! Do you know if they were all taken at the minimum focal length? Can you use the 24mm lens without vignetting? Could you perhaps show 100% crops from the relevant corners?

I’d say it’s a bull, but I’m not certain. I very much appreciate the thoughtful and balanced nature of this conversation! Thanks for all the links, they will keep me occupied over the weekend as I learn more.