Adapted Telephoto Lenses for Eclipse Shooting (GX680)

Hello all! These forums have been such a treasure trove of knowledge and I'm hoping to tap into it again. I have a Fuji GX680 and the longest lens I can find is a 300mm, equivalent to about a 150mm on 35mm. There's a 500mm, but apparently, you have a greater chance of hitting the lottery (unless someone has one, please PM me).

So, I found out Fuji made a Linhoff large format lens board adapter for the camera. I don't know where to begin looking, so figured I'd tap into community knowledge. What's the longest lens I can get that might fit the board to shoot the solar eclipse in April? I'd like to get some relatively close up shots of totality and the 300mm is still just too wide to get any good level of detail. I could also get "closer" by using a 6x4.5 back to get a tighter crop, but I'd like to shoot the 6x8, if possible. Anyone have any helpful insight to help me figure this out before my April trip?

A quick search tells me the sun has an angular size of 0.54°. Let's round to 0.5° and assume you want the sun to fill nearly half the frame height, 1" on the film. Then you'd need a lens of around 720" or 1800 mm if I got this right in my head. Look at telescopes or smaller format?

Appreciate the input, but unfortunately a telescope or smaller format isn't something I can do. Aiming to work with the equipment that I have and not outlay for a whole new setup when I have a perfectly good one with an interesting option.

Are there any decent sized large format lenses that might work in this use case?

Unfortunately to get photographs of sunspots, flares and the corona one needs a telescope with the appropriate camera adapter and filters.

UserDemos said:

Appreciate the input, but unfortunately a telescope or smaller format isn't something I can do. Aiming to work with the equipment that I have and not outlay for a whole new setup when I have a perfectly good one with an interesting option.

Are there any decent sized large format lenses that might work in this use case?

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Forget my math above, now I get around 3000 mm.
Either way, no idea about lenses that would do this, I'm veeery doubtful LF lenses in that range exist, the extension needed would be highly impractical, not to speak of support; process lenses maybe. You'd need to figure something out to focus such a lens; LF cameras use bellows. Support would also be your issue if you found such a thing. You sure can do something with shorter FLs, many people do, but you'll just have a small sun in lots of sky, I don't see the appeal, but again, many people do.
One more important thing I'm sure you're aware of, but for other readers of this thread: DO NOT LOOK INTO THE SUN through a camera! (Unless you have a solar filter made for this purpose installed in front of the lens.) The sun will burn holes in retinas as well as camera shutters.

grain elevator said:

Forget my math above, now I get around 3000 mm.
Either way, no idea about lenses that would do this, I'm veeery doubtful LF lenses in that range exist, the extension needed would be highly impractical, not to speak of support; process lenses maybe.

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No need for a lens that large. I can figure out a lovely composition with something smaller. I'm going to be in a highly urban area and can grab some skyscraper tops. Is there perhaps something out there in the ~1000mm range in LF? I don't know if there's a reflex lens in the LF world similar to what one might find in MF or 135.

grain elevator said:

You'd need to figure something out to focus such a lens; LF cameras use bellows.

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The GX680 is a bellows camera with a rail for focus, so that's a non-issue in my use case.

grain elevator said:

One more important thing I'm sure you're aware of, but for other readers of this thread: DO NOT LOOK INTO THE SUN through a camera! (Unless you have a solar filter made for this purpose installed in front of the lens.) The sun will burn holes in retinas as well as camera shutters.

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Good PSA! I only want to capture totality at this point, but if I change my mind, I have appropriate gear handy for that.

The issue with the bellows is how far they will need to be extended in order to focus such a long lens. Your camera isn’t designed to be able to focus lenses with focal lengths beyond 500mm so it might not be possible.

How much bellows would I need for a 700mm or 800mm or 1000mm? Is there a way to determine. I can also add 80mm extension rails to my body to make more room as well.

It depends on the design of the lens. Normal lenses have flange focal distances very close to their focal length so for those you would be looking at bellows extensions of ≈ 700mm, 800mm and 1m.

But some lenses are telephoto designs which gives them a shorter flange focal distance. For those you would see shorter bellows extensions but exactly how much shorter depends on the specific lens.

For example, the telephoto design of the Fujinon T 600mm f/12 gives it a flange focal distance of only ≈384mm which is just short enough to make it useable on my monorail 4x5 camera which has a maximum bellows extension of 19 inches.

If you had exactly 384mm of bellows extension you could focus the fujinon to infinity but no closer so you would be able to shoot the sun in isolation, but if you wanted to include any foreground objects they would be completely out of focus. Whereas with my camera’s 482mm of extension I could focus on objects as close as 4.3 meters away.

I haven't been able to find the max bellows extension on a GX680, but I do know that there is a 80mm extension rail set. If I had to guess, I'd expect that with the extension and long bellows it might get close to 300mm. The sun is at infinity, so assuming there is no closer items in the landscape you need to keep in focus as well, you should be able to use any lens (that fits the GX mount) with a focal length close to whatever you max bellows extension is. if its 300mm, you can probably use a 300mm lens, or you can look for a telephoto that is longer but still has a flange focal distance of 300mm or less.

The Nikkor T 360 has a FFD of about 260mm, with the 500mm rear it is 350mm.

Alternatively, depending on the design of the adapter, you can affix a top hat board. These lens boards extend the lens mount point out in front of the front standard. So a 4 inch extension would gain you 100mm, though they can vigniette if they're too long.

LF as well as a medium format camera like the GX are not really well adapted to ultra long focal lengths because a long bellows extension and top hat board will be pretty unstable. You can get very long lenses like 1200mm (48in) and sometimes in telephoto design, but even the Nikkor 1200mm telephoto still needs 760mm of bellows--something that the GX won't be able to do no matter what you try.

(remember, replace any use of "300mm" above with the actual real max extension of your camera.)

First of all this is a ridiculous impractical suggestion, but novoflex were compatible with Hasselblad(this might have required a larger diameter bellows to cover 6x6- which would be expensive and impossible to find) you would need two tripods, or a custom bracket, but the 640mm with a 2x converter is pretty long with most of the tube length supplied.
If you are traveling for the eclipse, yes it's a ridiculous suggestion.
I've been thinking about attaching a novoflex to a baby graphic for a while. I just haven't gotten around to it...

I took shots of the 1999 eclipse in Germany with 35mm format and a 350 Tamron mirror lens. After I compared mine with someone's shots with a 500mm lens, i wish I'd sourced a longer lens. 500 is just nice for this on 35mm, gives good detail but with some context around the disc. So I would say try to get at least 1000mm for the bigger format. Most telescopes and 1000mm photo mirror lenses will not be corrected for, or cover, a 6x8cm format, so you'd best use an LF tele lens.
Nikon had some long lenses up to 1200mm for LF. You need to find one you can borrow or rent though, as they are not cheap. You'll also need to DIY up some sort of rail to hold the camera and lens, because your Fuji bellows will still be miles away from the flange/shutter of the tele lens.
Sounds ambitious !