Not a huge fan of my GoPro

[Barmaglot]

Really? I must get that sticker and put in my mask objects that look like they are far away are much closer.

That looks like a fisheye shot from... 5 meters away? Maybe a bit more? For the big telephotos used by land photographers this is at the edge of minimum focus distance.

 

[Blackcrusader]

I disagree with OP on nearly everything he posted. GoPros are easy to use, very good on battery, get excellent videos and fairly good photos. If he finds it hard to use, then going to any other camera will make diving even harder for him. Only thing it really cannot do is macro. And I agree, you do not need a DSLR to get great photos, a TG-6 will give you great shots, especially macro.

As one who has gone from go Pro to TG6 I agree. For me I am not trying to take photos for some competition but for my vacation memories. It's does take time to learn settings and yes it is not a DSLR but I don't expect it to act like one either. For the US$500 I paid for my TG6 housing and extra kit I do not expect it to compete with gear that costs 4 of 5 times as much. I get 3 dives a day on a single battery for my go pro and TG6 at least 2 dives before a battery change but often 3.

 

[Blackcrusader]

That looks like a fisheye shot from... 5 meters away? Maybe a bit more? For the big telephotos used by land photographers this is at the edge of minimum focus distance.

More than 10m away with a go pro hero 4 black. I'm sure you can bring a big telephoto camera in the water if you want and can get a housing. This from a whale shark 15m above me with the go pro.

 

[Barmaglot]

More than 10m away with a go pro hero 4 black. I'm sure you can bring a big telephoto camera in the water if you want and can get a housing. This from a whale shark 15m above me with the go pro.

Again, context. I was replying to a post recommending to start with lenses and built the system around that. The really big and expensive lenses used in land photography are things like this, used to take photographs from hundreds of meters away - distances simply unachievable underwater. Yes, in extremely clear water, you can step back a little bit, more if you're willing to accept that your image will be composed largely of silhouettes. I've done it myself, at time, for example:

I was at ~25m, the school of barracudas was near the surface. I have never had an opportunity to shoot a tornado like this before, and I don't know when I will get one again, but I couldn't ditch the group and rocket upward, so I zoomed in a little bit on my 16-50 (36mm, so about halfway) and took the shot. I had to put it into black and white afterwards, and push it a LOT in post-processing to get what I got. Had I been within 5 meters of the school and shooting an ultrawide or fisheye, the results would've been spectacularly better - and this was in some of the clearest water that I've ever seen. Just a week before that, I was shooting this:

...in so much silt, I was having trouble seeing my own hands.

 

[bvbellomo]

For their price points, both gopro and tg6 are good products. If you are happy with them, I am happy for you. More underwater images exist for these than almost all cameras, and I have yet to find any I am happy with.

 

[bvbellomo]

Back to the sync issue. I understand something like the g7x, with 1/5000 second capturing the strobe, will have 20 times more light from the strobes relarive to ambient than a 1/250 second sync time. So I can buy cheaper strobes, turn them down, or do creative things.

What I don't understand is why the Pen 10, with its 1/250th second sync time is better than apsc cameras with 1/250th second sync times, or why those are better 1/250th second full frames.

I do understand that I will stop down for most underwater shots for depth of field and using strobes I won't need low light performance, which effectively negates most of the benefits of a larger sensor. And I understand generally full frames are more expensive and larger than apsc, which is more expensive and larger than 43. But I don't understand why deciding between a small weather sealed full frame I will use outside of diving vs a 43 in the same price range, I should favor the latter.

 

[Barmaglot]

Back to the sync issue. I understand something like the g7x, with 1/5000 second capturing the strobe, will have 20 times more light from the strobes relarive to ambient than a 1/250 second sync time. So I can buy cheaper strobes, turn them down, or do creative things.

Not quite. Strobes are fast, but not instantaneous. Their power is modulated by flash duration, i.e. the xenon bulb can't vary its brightness, but it can vary how long it stays burning for. A full-power flash on a Z-330 is approximately 3 milliseconds in duration (~1/320s). It's also not uniform over time - profiling with a light sensor and an oscilloscope shows the strobe rapidly (~0.2ms) going from nothing to maximum brightness, staying there while the capacitors keep dumping energy into it, then gradually (~1-1.5ms) fading back down to nothing. If you turn the power down, then the 'maximum brightness' period gets cut short, and thus the overall exposure is not as bright. At very low power levels, it cuts out and starts dimming before it even achieves the maximum brightness level.

What this means with regards to cameras with very fast flash sync capability (i.e. compacts) is that while you can sync very fast, going above 1/320-1/500 will start cutting into your strobe exposure if you use maximum power. If you use less than maximum power, then you can push the speeds higher without losing strobe light.

For my part, I generally sync at 1/160 (maximum afforded by my camera without HSS) for macro, and usually slower than that for wide-angle, although exact settings depend on lighting conditions. Since I'm using a moderately large sensor with a dome, I have to stop down quite a bit for sharpness (f/11 or more) and thus I'm using shutter speeds as slow as 1/50 and even pushing ISO up a bit in order to get nice, bright, blue background water.

I do understand that I will stop down for most underwater shots for depth of field and using strobes I won't need low light performance, which effectively negates most of the benefits of a larger sensor.

A larger sensor, all else being equal, will resolve more detail. Look up the concept of the Airy disc - the pixels on modern digital cameras are generally smaller than that, so while you can cram more pixels into a given sensor size, physics won't let you focus the light coming off a certain point of your subject onto an area smaller than the Airy disc limit for the given wavelength. However, if you make the sensor larger, it will accommodate more of those Airy disks, and even with the same amount of pixels, you will be better able to see finer features of the subject. It's worth pointing out though, that with depth of field limitations of these larger sensors, you will find yourself using smaller and smaller apertures to get more DoF, and at some point, you will start losing that extra detail to diffraction.

But I don't understand why deciding between a small weather sealed full frame I will use outside of diving vs a 43 in the same price range, I should favor the latter.

The full frame camera will usually use much larger and more expensive ports, particularly domes. M43 and APS-C rectilinear wide-angles are usually shot with 170-180mm domes, which are reasonably compact, but full-frame cameras typically use 230mm domes, and these are enormous - the numbers really don't convey how huge they are. Wet lenses can be used to sidestep that issue, but the wet wide lenses currently on the market generally target compact cameras, and most full-frame cameras lack lenses capable of working in conjunction with a wet wide lens. One notable exception is the Sony A7 series - the Sony 28mm prime and Nauticam WWL-1 can work together, and the 28-60mm kit zoom (recently released as a companion to A7C) is also said to work perfectly with the WWL-1, giving better results than 16-35mm lens in a huge dome.

An additional factor is that many people are unwilling to risk their expensive camera (an A7R IV is $3k for body alone) and potentially equally expensive lenses by taking them underwater. Even the highest quality and most expensive housings can leak or flood, and in some emergencies, you may lose your system altogether. Losing a $500-1000 system is far less painful than a $5000-10000 one. While it's possible to build a full-frame system for the same or lower price than an M43 one, you really have to work at it - for instance, compare a used A7 III body in a SeaFrogs housing to a brand new E-M1X in Nauticam.

 

[bvbellomo]

The Sony a7 series (and possibly the a9) has faster flash sync speeds than the a6 or anything Canon makes and they are weather sealed. I am much more comfortable taking a full frame weather sealed DSLR I got off ebay for $500 on a boat than a $1500 brand new 4:3 that was designed for indoor use. Yes, my whole setup might cost $5000, but most of the accidents involving total loss of camera, lenses, housing and strobes are accidents where they never find my dead body.

I realize the limitations of just throwing this into a Seafrogs housing with whatever lens fits, and I admit a G7X setup might take better pictures. If I am going to the Red Sea, I want to see the Pyramids and Luxor and over the next 10 years, will take 100 good pictures above water for every 1 I take underwater. I can't justify a $1000+ underwater only system when I am going to want to continue to invest in a land use camera (whether my current Canon or an upgrade) and the more I invest in my land camera and use it, the more I am going to want a DSLR under water.

 

[Barmaglot]

The Sony a7 series (and possibly the a9) has faster flash sync speeds than the a6 or anything Canon makes and they are weather sealed.

I am not particularly familiar with Canon's lineup, but Sony cameras are limited to 1/160 flash sync speed, with 1/250 possible (on A7/A9, not A6xxx) if you use a TTL-capable trigger. You don't have to use the strobes in TTL mode, but the 1/250 speed depends on the very precise timing provided by triggers that communicate with the camera using Sony's flash protocol. A6xxx cameras are limited to 1/160, period. The only way to exceed this is to use high-speed sync, which requires a compatible trigger (TRT, UWT) and strobes (Retra Prime/Pro) and drastically reduces strobe power output. The one exception is the new A1, which is capable of 1/400 in full-frame mode and 1/500 in APS-C crop, but that's a $6500 body.
Another point of note is that all the Sony full-frame cameras lack a pop-up flash, and thus strobe triggering must go over an electric sync cable, or via an add-on LED trigger.

 

[bvbellomo]

From a practical standpoint, what would that mean connecting a synchro cable to a Z-330 and having a 2nd Z-330 without a cable as a slave?

I don't think there is any Seafrogs housing for a weatherproof camera with a popup flash except the Sony a6 line.