Cavern photography questions

pthrift

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Curious as to suggestions for cavern photography. Thinking about making a trip to luray caverns tomorrow or Tuesday; and I'm wanting to take some photos while I'm there. Im not sure if I should take more than my two fastest lenses (a 35/1.8 & 50/1.8)...ie do I need to take a tripod or flash or etc? I assume a flash is useless in such a big space.


Thanks in advance

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TCampbell

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Flash has the "inverse square law" issue of light fall-off. The intensity of the light halves each time the distance from the flash increases by a factor of the square root of 2 (about 1.4).

e.g. at 7' you get half as much intensity as you get at 5'. At 10' you get half as much as you get at 7'. At 14' you get half of 10'. At 20' you get half of 14'. At you just keep going.

When you get way out there... 70' is about half the light of 50' ... but it takes a span of 20' for the drop-off to occur. It's the nearby distances where the drop-off is REALLY noticeable... and of course if there was something much closer (say 10' away) then it would get about 30x more light then the object at 50'.

Assuming the cave has strategically placed interior lights (from the videos I can find on the Internet it looks like they do), you might do better on the ambient lighting *if* the camera is on a tripod so you can afford to take a long enough exposure. I'd bring the tripod... assuming they permit those.

Also.... wide angle will work better. You'll see more of it -- and also wide angles tend to "stretch" the size of the space making the interior seem larger. The wide angle will naturally offer better depth of field, but check the DoF and don't cheat it just because you don't have much light. If you're on a tripod and the cave isn't moving (and if it is moving you have bigger problems to worry about) you can take all the time you need to get that exposure. If you cheat the DoF you'll have some stuff in focus and other stuff out of focus and you'll likely be disappointed.

Using a 30mm lens on an APS-C body:
At f/5.6 the hyper focal distance of a 30mm lens on an APS-C body is about 26'. That would give you everything from about 14' to infinity in-focus.
At f/4 the hyper focal distance increases to 37' giving you focus from 26' to infinity.
But if you drop all the way down to f/1.8 the hyper focal distance changes to 83' giving you everything from about 41' to infinity in-focus. If you were to focus closer... say 20'... then you only get 16-26' in focus.

You're basically trying to shoot a "landscape" inside... you want everything in focus from front to back. For landscapes, you normally go to high f-stops to make that happen. e.g. f/11 or f/16.
At f/8 you get a hyper-focal distance of 18.6' and everything from just below 10' to infinity is in focus. At ISO 1600 using only interior rooms with table lamps at f/8, my meter shows the dim room still has enough light to allow for a 1/4 sec exposure at f/8. Judging from the lighting in the videos... they seem to do a fairly decent job lighting up the place... so I'm guessing with a tripod you'd still be taking sub-second exposures at high f-stops.
 

Light Guru

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Any tourist cave is not going to give you the access you will need unless you make special arrangements. And even then they may not let you off the designated paths to place flashes.

Your gonna want to check this video out because cave photography is probably a LOT more complicated then you are thinking.

http://petapixel.com/2014/06/28/interesting-bts-look-takes-cave-photographer/
 
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pthrift

pthrift

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Any tourist cave is not going to give you the access you will need unless you make special arrangements. And even then they may not let you off the designated paths to place flashes.

Your gonna want to check this video out because cave photography is probably a LOT more complicated then you are thinking.

http://petapixel.com/2014/06/28/interesting-bts-look-takes-cave-photographer/
Thanks for the link, and advice. I assumed I was not going take amazing shots down here but was hoping for something at least worth a digital share.

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pthrift

pthrift

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Flash has the "inverse square law" issue of light fall-off. The intensity of the light halves each time the distance from the flash increases by a factor of the square root of 2 (about 1.4).

e.g. at 7' you get half as much intensity as you get at 5'. At 10' you get half as much as you get at 7'. At 14' you get half of 10'. At 20' you get half of 14'. At you just keep going.

When you get way out there... 70' is about half the light of 50' ... but it takes a span of 20' for the drop-off to occur. It's the nearby distances where the drop-off is REALLY noticeable... and of course if there was something much closer (say 10' away) then it would get about 30x more light then the object at 50'.

Assuming the cave has strategically placed interior lights (from the videos I can find on the Internet it looks like they do), you might do better on the ambient lighting *if* the camera is on a tripod so you can afford to take a long enough exposure. I'd bring the tripod... assuming they permit those.

Also.... wide angle will work better. You'll see more of it -- and also wide angles tend to "stretch" the size of the space making the interior seem larger. The wide angle will naturally offer better depth of field, but check the DoF and don't cheat it just because you don't have much light. If you're on a tripod and the cave isn't moving (and if it is moving you have bigger problems to worry about) you can take all the time you need to get that exposure. If you cheat the DoF you'll have some stuff in focus and other stuff out of focus and you'll likely be disappointed.

Using a 30mm lens on an APS-C body:
At f/5.6 the hyper focal distance of a 30mm lens on an APS-C body is about 26'. That would give you everything from about 14' to infinity in-focus.
At f/4 the hyper focal distance increases to 37' giving you focus from 26' to infinity.
But if you drop all the way down to f/1.8 the hyper focal distance changes to 83' giving you everything from about 41' to infinity in-focus. If you were to focus closer... say 20'... then you only get 16-26' in focus.

You're basically trying to shoot a "landscape" inside... you want everything in focus from front to back. For landscapes, you normally go to high f-stops to make that happen. e.g. f/11 or f/16.
At f/8 you get a hyper-focal distance of 18.6' and everything from just below 10' to infinity is in focus. At ISO 1600 using only interior rooms with table lamps at f/8, my meter shows the dim room still has enough light to allow for a 1/4 sec exposure at f/8. Judging from the lighting in the videos... they seem to do a fairly decent job lighting up the place... so I'm guessing with a tripod you'd still be taking sub-second exposures at high f-stops.
This the type info I was curious about. Ie lens choice; exposure time; etc.


I don't have enough flash for this I don't think.. all I have is the sb400 & a yunonguo yn560-ii. The 560ii may be close but I'm honestly not comfortable enough with it yet, I'd rather use what little ambient lighting is available

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Kanthaka

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Curious as to suggestions for cavern photography. Thinking about making a trip to luray caverns tomorrow or Tuesday; and I'm wanting to take some photos while I'm there. Im not sure if I should take more than my two fastest lenses (a 35/1.8 & 50/1.8)...ie do I need to take a tripod or flash or etc? I assume a flash is useless in such a big space.


Thanks in advance

Sent from my Samsung Galaxy S4; probably while slacking off at work

I went to Luray Caverns a few years ago. I don't remember which tour I took but I was able to get decent photos from a P&S. They don't allow you to use flash but it is well lit. However, my tour group bumped into another tour group & I saw all of them have flashlights, headlights, etc. So, I guess, the amount of lighting differs depending on which tour you get.
 

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