Well I finally broke down and bought a set of Kenko extension tubes for my 450D. I know the image is slightly overexposed, but I am still working out the kinks of shooting in Manual mode. I am liking the combo so far. Any input would be appreciated.
First try with extension tubes and image stacking
- Thread starter ataylo13
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I'm jealous!!! I wonder if I can do a good IS with the canon SX20IS... wait, do you think the IS in my camera name means.... hm, brb google.
Many objective lens reviews will simply abbreviate chromatic aberration as "CA" on their review charts. The source of CA entirely in the lens (not the body), and every lens has it to some degree. It varies with aperture, focal length, and location (worse at the edge than at the center of the lens).
Here's one way of describing it. It's a bit of color that bleeds off the edges of objects in the image. It looks sort of like a halo, and in your pic its purple-pink. It's easier to see if you zoom to 200% on the photo, but it can be noticeable without zooming in. I see it very often in photos of egg crate.
Just thinking out loud here. Since the Canon 100mm is a well-regarded lens, I'm guessing its the kenkos. But then again, I'm not sure if the stacking process can contribute to the effect.
Sorry about being a nit-pick. I've been on the fence for over a year as to whether I'd get a set of Kenkos, so I was especially curious to see the image quality that one can get with them. I wonder if it would be better to simply stack and do a crop of the image without using the extension tube.
Here's one way of describing it. It's a bit of color that bleeds off the edges of objects in the image. It looks sort of like a halo, and in your pic its purple-pink. It's easier to see if you zoom to 200% on the photo, but it can be noticeable without zooming in. I see it very often in photos of egg crate.
Just thinking out loud here. Since the Canon 100mm is a well-regarded lens, I'm guessing its the kenkos. But then again, I'm not sure if the stacking process can contribute to the effect.
Sorry about being a nit-pick. I've been on the fence for over a year as to whether I'd get a set of Kenkos, so I was especially curious to see the image quality that one can get with them. I wonder if it would be better to simply stack and do a crop of the image without using the extension tube.
I'm not seeing any chromatic aberration. There are some areas that look like it, but those are a function of tank lighting and the way it passes through coral tissue. Some may be caused by the glass. If you're shooting through acrylic it can cause a rainbow effect that appears to be chromatic aberration. It's the acrylic doing it, not your lens. It will be more pronounced with thicker acrylic and can be a real pain with cheap acrylic. What I see in your image is expected, particularly with the tissue structure of chalices, and negligible.
You lens is not introducing any chromatic aberration. If it was, Canon wouldn't be able to sell a single 100-mm macor lens because no macro shooter would use it. Your extension tubes can't introduce CA because they have no glass. They simply change the point at which the image lands on the sensor.
What I do see is multiple edges in the back of the coral/top of your stacked image. There is also indication of multiple edges in some of the other nodules in the image. Those result when either the coral or your camera moves when you're shooting the stack. Once that happens, the overall image is ruined because you'll have those multiple edges and the rest of the image will not be sharp.
You must have a sturdy tripod to do this kind of photography and use a remote release or timer and mirror lockup to minimize any chance of camera movement. Flow must be shut off. Even then you can get movement as the coral contracts or expands its tissue while you're shooting the stack. I had a trach shot a couple of weeks ago that was going to be an absolute stunner. I shot the stack twice and both times the coral expanded/contracted, ruining both shots. I didn't see the movement while I was shooting because it was slow and subtle. But it was very obvious when I combined the stack. I'm still mad about it, but nothing I can do.
To see a clear example of the multiple edges I'm talking about, look in the upper right quadrant of this shot. You'll see where tentacles in one of the zoanthid polyps moved while I was shooting the stack, creating multiple edges. This is very common with zoanthid stacks.
Gary
You lens is not introducing any chromatic aberration. If it was, Canon wouldn't be able to sell a single 100-mm macor lens because no macro shooter would use it. Your extension tubes can't introduce CA because they have no glass. They simply change the point at which the image lands on the sensor.
What I do see is multiple edges in the back of the coral/top of your stacked image. There is also indication of multiple edges in some of the other nodules in the image. Those result when either the coral or your camera moves when you're shooting the stack. Once that happens, the overall image is ruined because you'll have those multiple edges and the rest of the image will not be sharp.
You must have a sturdy tripod to do this kind of photography and use a remote release or timer and mirror lockup to minimize any chance of camera movement. Flow must be shut off. Even then you can get movement as the coral contracts or expands its tissue while you're shooting the stack. I had a trach shot a couple of weeks ago that was going to be an absolute stunner. I shot the stack twice and both times the coral expanded/contracted, ruining both shots. I didn't see the movement while I was shooting because it was slow and subtle. But it was very obvious when I combined the stack. I'm still mad about it, but nothing I can do.
To see a clear example of the multiple edges I'm talking about, look in the upper right quadrant of this shot. You'll see where tentacles in one of the zoanthid polyps moved while I was shooting the stack, creating multiple edges. This is very common with zoanthid stacks.
Gary
If I recall, you live in Illinois and possibly not too far from me. Maybe we could set up a time for me to visit, photograph your corals, and help you with your photography. Send me a PM. If you're not in Illinois, let me know where you're at. I travel frequently and might be coming to your town in the future.
Gary
Gary
Some more on stacking:
Use an aperture in the f/8 to f/14 range. Just choose one. Make sure your focus is precise and that you overlap the DOF with each shot. You need to shoot the stack so it covers all of the image to get the effect you desire. You stopped the stack part way through the scene and got a resulting stacked image that could have been achieved with a single shot at f/22. Your shot is also over exposed on the top side of the coral. Cut the shutter speed by a stop (or maybe more) so you eliminate the blown areas. You'll create darker areas in the foreground, but you can correct them in Photoshop. Better to do that than have blown areas that are distracting and ruin the overall shot.
Chalices can be difficult to stack because their many nodules cause a ton of reflection points and light bounces all over in all of the those mountains and canyons. It's also typical that your chalice will be backlit, which appears to be the case in your shot. That's because we tend to put the chalices in the front of the aquarium and the lights, centered over the tank, are usually behind the chalice. The backlighting lights the backside of the nodules and will also create a bright rim on the top of the nodules. Nothing you can do about that other than make sure any blown areas are minimized.
In the example below you, I've shot across the surface of a chalice. You can see that I've carried the stack through the entire scene so that all of the chalice is in focus. This is what you want. This also is an example of the backlit factor. You can see that the rims of most of the nodules have a bright halo.
Hope all of this helps,
Gary
Use an aperture in the f/8 to f/14 range. Just choose one. Make sure your focus is precise and that you overlap the DOF with each shot. You need to shoot the stack so it covers all of the image to get the effect you desire. You stopped the stack part way through the scene and got a resulting stacked image that could have been achieved with a single shot at f/22. Your shot is also over exposed on the top side of the coral. Cut the shutter speed by a stop (or maybe more) so you eliminate the blown areas. You'll create darker areas in the foreground, but you can correct them in Photoshop. Better to do that than have blown areas that are distracting and ruin the overall shot.
Chalices can be difficult to stack because their many nodules cause a ton of reflection points and light bounces all over in all of the those mountains and canyons. It's also typical that your chalice will be backlit, which appears to be the case in your shot. That's because we tend to put the chalices in the front of the aquarium and the lights, centered over the tank, are usually behind the chalice. The backlighting lights the backside of the nodules and will also create a bright rim on the top of the nodules. Nothing you can do about that other than make sure any blown areas are minimized.
In the example below you, I've shot across the surface of a chalice. You can see that I've carried the stack through the entire scene so that all of the chalice is in focus. This is what you want. This also is an example of the backlit factor. You can see that the rims of most of the nodules have a bright halo.
Hope all of this helps,
Gary
Thank you for the great tips Gary. I didn't realize there needed to be that much overlap when stacking images. I was F/2.8 to try and get as sharp a picture as I could. I have a very old, but sturdy tripod and I was using a remote release and mirror lockup to help with image stabilization. I am assuming that any movement came from me adjusting the focus.
Your DOF at f/2.8 is paper thin. So thin, that you won't be able to overlap the DOF. If you don't overlap the DOF, the stacking software can't match up sharp areas from image to image and you get a bunch of OOF areas.
Make sure your camera/tripod is locked down tight and when you focus for each shot, make sure you remove your hands from the camera and allow it to settle before taking the shot.
And you're more than welcome. Always glad to help.
Gary
Make sure your camera/tripod is locked down tight and when you focus for each shot, make sure you remove your hands from the camera and allow it to settle before taking the shot.
And you're more than welcome. Always glad to help.
Gary
Thanks for clearing that up, Gary.
FWIW, ataylo13, I'll post this afternoon a side-by-side of a couple areas where I saw some things. Just so you'll get an idea of what I noticed. The unstacked version does not have the effect, so it's an artifact of the stacking process.
FWIW, ataylo13, I'll post this afternoon a side-by-side of a couple areas where I saw some things. Just so you'll get an idea of what I noticed. The unstacked version does not have the effect, so it's an artifact of the stacking process.
Well, here are a few spots that stood out to me. I limited them to the more focused area of the second photo you posted, but they're all over the place if you look carefully.
I hope that this makes my earlier post a little more clear. In the part that I've framed here, the most obvious spot is above the mouth of the coral. Notice the purple mustache?
Gary, I'm not seeing a halo effect in your photo. I understand that the edges of the bumps are brighter than the center of each bump, but this isn't what I meant by the halo that I saw in ataylo13's photo. If I had to make another description of the effect I noticed, I suppose it could be called a ghosted outline that shouldn't be there.
I hope that this makes my earlier post a little more clear. In the part that I've framed here, the most obvious spot is above the mouth of the coral. Notice the purple mustache?
Gary, I'm not seeing a halo effect in your photo. I understand that the edges of the bumps are brighter than the center of each bump, but this isn't what I meant by the halo that I saw in ataylo13's photo. If I had to make another description of the effect I noticed, I suppose it could be called a ghosted outline that shouldn't be there.
cparka,
The areas you point out are a result of lack of DOF overlap that resulted from the f/2.8 aperture he used. In other words, you can't get any overlap at f/2.8 with macro shots because there's essentially nothing to overlap. The end result is blur throughout the image. I'm sure the next attempt will produce much better results.
Agreed on my photo. I called the brighter top edges of the nodules halos, but ghosted outline works, too. It's just the strong light reflecting off the backside of those nodules.
Gary
The areas you point out are a result of lack of DOF overlap that resulted from the f/2.8 aperture he used. In other words, you can't get any overlap at f/2.8 with macro shots because there's essentially nothing to overlap. The end result is blur throughout the image. I'm sure the next attempt will produce much better results.
Agreed on my photo. I called the brighter top edges of the nodules halos, but ghosted outline works, too. It's just the strong light reflecting off the backside of those nodules.
Gary
