Can't help you with camera/exposure issues, but...

Read the two images (cave; figure jumping) into separate layers (File->Open as Layers) Make sure the Layers dock is visible. Make sure the figure layer is above the cave layer; Add an alpha channel to the figure layer; duplicate the figure layer and make it invisible (unclick the eyeball at the beginning of the layer); (this is in case something unfixable happens to the copy of the figure layer that you will be working on); erase everything from the figure layer but what you want; [one can use a layer mask to accomplish the same thing "non-destructively", at the cost of making the process more complicated for the beginner (like myself, also!)] move/scale/rotate/... the figure layer to place it where you want.

File->Save(or Save As) .xcf so that you can do more with this image merge project some other time; File->Export (or Export As) to whatever image format you like .jpg/.png/...

-Scott Jacobs

-----Original Message----- From: mikej411
To: gimp-user-list
Cc: notifications
Sent: Fri, Feb 24, 2017 6:07 pm
Subject: [Gimp-user] Add frozen object from short exposure frame to long exposure frame

Hello, I'm not sure if I am posting this on the forum, or if these are supportmessages? If I am not posting this in the correct area, please feel free to movethis for me, or let me know what area I should post if to...I am going on a trip to the Yucatan in May and want to take good pictures insidesome of the Cenotes (sinkoles that expose groundwater underneath). Some of thesecenotes are underground with not much light (Beams of light from the sun comethrough from the holes at the top of the cave, and some stationary artificiallighting is provided from the people who work at these caves as well).So my plan is to use my Rokinon 12mm f2.0 with my Sony A6000 on a tripod and setit to max aperture and long exposure, with maybe ISO of about 400 to 800. Dothose settings sound about right to get some good low-lit cave pictures? Wouldthere be any reason to lower the aperture? Keep in mind, I do not plan on goingany further and setting up external light sources, etc. The cave should be litenough to be able to grab a decent picture with long exposure.Anyway, the more important question or concern I have comes into play when Iwant to get some action shots or get a person into that long exposure photo,i.e. freeze the person when jumping into the water (in the air mid-jump). Ithink the only way to do that is with a computer program using layers or masks,correct? I don’t want to purchase anything, and I think this can be accomplishedwith GIMP on my Macbook pro.Last night, I tried masking myself out of a picture (or whatever the term is),but it was very hard to do in terms of being precise. I tried to fiddle aroundwith the lasso and the different detections (color/shape/contrast), to no avail.Maybe part of that was because I was on a small laptop without using a mouse.But I think most of it was because I am an extreme beginner and this is my firsttime playing around with phot editing tools.Can someone please point me to some detailed Gimp tutorial videos either showinghow to accomplish exactly what I want from start to finish (Add the frozenperson from the short exposure frame to the long exposure frame), or if youdon’t know of a video that explains all of that, then maybe some tutorials onsomething similar, like how to precisely mask out people.-- mikej411 (via www.gimpusers.com/forums)_______________________________________________gimp-user-list mailing listList address: gimp-user-list@gnome.orgList membership: https://mail.gnome.org/mailman/listinfo/gimp-user-listList archives: https://mail.gnome.org/archives/gimp-user-list

stationary artificiallighting is provided from the people who work at these caves as well).So my plan is to use my Rokinon 12mm f2.0 with my Sony A6000 on a tripod and setit to max aperture and long exposure, with maybe ISO of about 400 to 800. Dothose settings sound about right to get some good low-lit cave pictures?

For the long exposure, use the lowest native ISO your camera has (don't use any "extended" ISO values your camera might offer.) There is nothing to be gained by going to 400 or 800 except a shorter exposure time (which can be relevant, but in your case sounds like it isn't). For the fast one, I'd use the widest aperture the lens has, the longest shutter speed you can afford given the motion you want to capture, and then set the minimal ISO to get the exposure.

Wouldthere be any reason to lower the aperture?

There might be -- if you have the luxury of a tripod and long exposures, you can narrow the aperture either to get better sharpness from the lens (most, but not all, will be sharpest a couple stops up from the widest aperture -- you can research the lens online; unfortunately dxomark.com doesn't cover that lens), or to get more depth of field. f2 is going to be pretty shallow. Might be cool, might not.

You might look into image averaging (usually taking the median, actually, as opposed to the mean)... I was just experimenting with a GIMP workflow for that and it's pretty great. It's useful for taking low-light pictures without a tripod, especially if you want to use higher shutter speeds.

You also might think about longer focal length lenses. I love 12mm, and that's what I would take first in your situation, but if any of the geometry of the caves allows for farther shots (i don't know how big they are), you can use the telephoto effect to enlarge the background... it can be a neat effect
.
Also, if you don't have many options of where to set up for a shot, e.g. because you're straddling a stream and balancing on a boulder or whatever, having a zoom gives some flexibility.

-c

If I read you right, you will be time exposing the cave overall. I'd suggest starting with ISO 200 to keep the noise down and the time exposure relatively short. Switch "on" long exposure noise reduction if you have it on your camera.

Then you want a short-duration shot of someone to: "freeze the person when jumping into the water (in the air mid-jump). "

Is there water in the cave that they will be jumping into? If so, just expose a hand-held flash during the jump during the long exposure. Set it to work with your max f-stop, or whatever f-stop you will be using, and at the distance the jumper will be from the flash.

Otherwise, I guess you will have to photograph the jumper either in a dark swimming pool or at a lake at night, again using flash and a short duration speed (1/200/sec, 1/250/sec). You may have front/rear curtain adjustments that allow you to show motion trails. See your camera manual.

Good luck, Rick S.

-----Original Message----- From: mikej411
Sent: Friday, February 24, 2017 1:45 PM To: gimp-user-list@gnome.org
Cc: notifications@gimpusers.com
Subject: [Gimp-user] Add frozen object from short exposure frame to long exposure frame

Hello, I'm not sure if I am posting this on the forum, or if these are support
messages? If I am not posting this in the correct area, please feel free to move
this for me, or let me know what area I should post if to...

I am going on a trip to the Yucatan in May and want to take good pictures inside
some of the Cenotes (sinkoles that expose groundwater underneath). Some of these
cenotes are underground with not much light (Beams of light from the sun come
through from the holes at the top of the cave, and some stationary artificial
lighting is provided from the people who work at these caves as well).

So my plan is to use my Rokinon 12mm f2.0 with my Sony A6000 on a tripod and set
it to max aperture and long exposure, with maybe ISO of about 400 to 800. Do those settings sound about right to get some good low-lit cave pictures? Would
there be any reason to lower the aperture? Keep in mind, I do not plan on going
any further and setting up external light sources, etc. The cave should be lit
enough to be able to grab a decent picture with long exposure.

Anyway, the more important question or concern I have comes into play when I want to get some action shots or get a person into that long exposure photo, i.e. freeze the person when jumping into the water (in the air mid-jump). I think the only way to do that is with a computer program using layers or masks,
correct? I don’t want to purchase anything, and I think this can be accomplished
with GIMP on my Macbook pro.

Last night, I tried masking myself out of a picture (or whatever the term is),
but it was very hard to do in terms of being precise. I tried to fiddle around
with the lasso and the different detections (color/shape/contrast), to no avail.
Maybe part of that was because I was on a small laptop without using a mouse.
But I think most of it was because I am an extreme beginner and this is my first
time playing around with phot editing tools.

Can someone please point me to some detailed Gimp tutorial videos either showing
how to accomplish exactly what I want from start to finish (Add the frozen person from the short exposure frame to the long exposure frame), or if you don’t know of a video that explains all of that, then maybe some tutorials on
something similar, like how to precisely mask out people.

mikej411 (via www.gimpusers.com/forums)