I shot on a DSLR and tried to move the camera closer to zoom, since DSLRs don't come with constant aperture lenses. But it didn't have the same zoom effect I wanted and got some shots of actual zooming. They look a lot better, accept the aperture changes. How do I change it to all look the same? I saw a tutorial for a synthetic aperture on After Effects, but have been having trouble applying it, that no tutorials go into much detail of the whole process. Any advice? Thanks.
Adjusting aperture in post.
- Thread starter ironpony
- Start date
paulears
Veteran
Are you having problems with exposure or depth of field? Or are you trying to make a physical track in look like a zoom - I'm not quite sure which aperture 'feature' is causing the grief? I don't use DSLRs for video, but do you mean that exposure can only done on auto? I'd always assumed that DSLRs had a video mode with aperture priority - don't they? As serious flaw if they don't.
handsome pete
Well-known member
He's talking about shooting something with a lens that doesn't have a constant aperture throughout the zoom range. You can certainly set your exposure manually, but in this case the lens has limitations. So I'm assuming in the particular shot he wants to correct, as the camera zooms in on the subject the image gets darker because the lens is forced to change apertures settings mid-zoom.
You can try to fix this in post, but I'd personally just re-shoot. And if you really want that zoom then find a lens with constant aperture. As far as correcting your original shot though it should just be your standard color correction. But the reason I suggest re-shooting is because you're essentially trying to color correct under exposed footage. There's only so much you can get out of that.
paulears
Veteran
Ah - gotcha. While I appreciate the plus points of DSLRs, not being able to zoom while shooting is a somewhat big limitation. I assume the aperture doesn't change too much? What is it? a stop or two? How do people get around this problem, or do they just avoid using the zoom live, and track in and out as a matter of course?
gonzo_entertainment
Veteran
Not a failing of DSLR, but of the lens. They make lenses that are constant aperture that would not have done that on your DSLR, they are just generally more expensive. Not something you'd find on a kit lens or mid range zoom for sure.
Zooming in general is frowned on by a lot of people (if you're talking about narrative film). There are directors and film styles that use it, but in general you'll find a dolly, crane, jib, etc... used a lot more than zoom.
j1clark@ucsd.edu
Veteran
I think dollying in or out is the current 'more acceptable' form of changing things. The 'powerzoom' was pretty much a novel technique for the late 60's early 70's, and a 'standard' for Hong Kong Kungfu films... then there's Austin Powers...
Otherwise the times where there may be a zoom, it usually is a slow creep, and not that much change, hence could be done with a uncorrected 35mm zoom...
As for compensating for brightness changes due to noncompensated aperture changes in the zoom lens, probably just a keyframed 'brightness' change would help a lot for a 'simplistic' fix.
Personally I use my 'kit' GH-1 14-140mm lens, and only use it as a 'fixed' lens, which can easily be changed out between shots...
j1clark@ucsd.edu
Veteran
I believe that references to 'synthetic aperture' in After Effects refers to the fact that After Effects has the ability to do simplistic '3-d'. It is simplistic because one can only have 2-d compositions, but they can be placed in 'depth' relationships, or the 'z' axis. So one can have a 'pasteboard' of a still or clip, at z depth 100, another at z dept 0, and yet another at z -100.
Using the 'synthetic aperture', then one can have sharp focus on the composition at z depth 0, and then the compositions at z 100, and -100 would be 'blurred' as if the virtual camera had DoF. You can keyframe the aperture changes and do a rack focus effect, moving the plane of sharp focus from say, the composition at z 100, to z -100 and passing through z 0.
One can also have illuminations in After Effects, and I believe the 'synthetic aperture' would affect the resulting 'brightness' of object that have been designated as illuminated...
I'm sure Video Copilot has tutorials on this sort of thing, but I don't have time now to give specific examples...
gonzo_entertainment
Veteran
I would agree with you, but zooming does have fans.
j1clark@ucsd.edu
Veteran
Yeah, I guess there has been a comeback of sorts with the 'reality' TV style, along with shaky cam, focus hunt, etc.
But again, the films that I've watched, that I liked or could put up with such, the techniques have been much more subdued than the 'power zoom'...
bgodoy
Active member
As stated, it seems to me that what your after is a constant exposure while zooming in on your lens. As jclark said, dollying in is a more acceptable form of changing frame composition and depending on the lens your using there can be a limitations. Nonetheless, there is a simple solution to your problem. You can either use your waveform monitor and ride your exposure whilst filming or send your footage through a program or software after the fact and check the IRE of your footage to keep it all at a constant level (ie. ideallly 1.0 IRE). Again, there is only so much post can remedy, however, if a constant exposure is the more important to you over the noise level in your footage, then checking your exposure after filming might not be a bad idea.
-B
-B
gonzo_entertainment
Veteran
It would be impossible to ride the exposure unless you had a cine lens or a de-clicked stills lens.
bgodoy
Active member
Right, I guess I should have offered that piece of information. :thumbsup: Good look Gonzo.
-B
Yes I'm talking the zoom becoming darker as I zoom in. I know the dolly has become more acceptable, but I like doing the power zoom. Especially in shots, where I want to zoom in far and fast, where it would not be physically possible to move in with a dolly in such a short amount of time. I was hoping to shoot shorts, with power zooms, but I guess if that's impossible with DSLRs...?
j1clark@ucsd.edu
Veteran
No. You just have to pay more for 35mm zoom, that has constant aperture. Since for still this is not an absolute need, it's not in the cheaper lenses.
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bgodoy
Active member
Ride your exposure in post (that is, if cine lenses aren't in your budget). In AE, if you add the Exposure effect and key frame the exposure slider while zooming you might be able to get away with it. In most cases, you shoulnt have too much of a problem, however, try not too over do it too drastically. I recommend adding some kind noise reduction to help with the darker areas in your footage. Of course if reshooting is a possibility and you can get a hold of a 35mm zoom (if you rent it, a decent lens will go for about $500 a day), that would be the most optimal solution.
-B
-B
Okay thanks, I have experimented with adjusting the aperture, but it makes the footage look too different from the other shots. Can I make the picture look the same as the other shots, afterwords? As for future shoots, sure I will dolly next time, but dolly-ing creates a bit of a rough zoom and does not have the same effect as that smooth zoom. Or maybe I just need a smoother dolly? What about rooms where there is carpet?
bgodoy
Active member
You can always color correct a single clip to match the rest of your shots (for the most part). Essentially, that's what color correction is intended to do. That's why a single film or motion picture will have several cameras in which the movie was shot but every shot always matches the previous one, as if it was filmed entirely on a single camera. If you having trouble getting your footage to cut together nicely, it's tough to decifer where the primary source of the problem arises (since it could be a multitude of things but if colored correctly and shot with the same camera, under the same lighting conditions, there shouldn't be too many issues getting it all to match).
As far as a dolly is concerned, I wouldn't be the authority on that particular aspect, given the fact that I don't specialize in that area. Perhaps someone else can fill you in better than I.
If it's the power zoom look your after, however, you could always use your dolly and retime your footage so that it's faster as you dolly in or out. I have personally never tried it, although, you can try it on future shoots and see if it satisfies your power zoom needs.
-B
As far as a dolly is concerned, I wouldn't be the authority on that particular aspect, given the fact that I don't specialize in that area. Perhaps someone else can fill you in better than I.
If it's the power zoom look your after, however, you could always use your dolly and retime your footage so that it's faster as you dolly in or out. I have personally never tried it, although, you can try it on future shoots and see if it satisfies your power zoom needs.
-B
bgodoy
Active member
Noise reduction would definitely help. Typically, color correction won't solve the problem. Here's a post I posted a while back regarding several noise reduction options:
http://www.dvxuser.com/V6/showthread.php?269969-Removing-Noise-From-Footage
Again, depending on your particular needs you may or may not be satisfied with the final result. I would recommend giving it a try at the very least.
-B
http://www.dvxuser.com/V6/showthread.php?269969-Removing-Noise-From-Footage
Again, depending on your particular needs you may or may not be satisfied with the final result. I would recommend giving it a try at the very least.
-B
