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I have a problem with aperture when I zoom with my DSLR.

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harmonica44

Default I have a problem with aperture when I zoom with my DSLR.
I was told before if I want to do a zoom shot with my DSLR, that in order for the aperture to not change, I have to lock it at at least f5.6. Here is a shot at sunset at f11:

https://www.youtube.com/watch?v=4Kk7gMefDBo

Even though if's at f11 the whole time, it seems to me that the exposure changes as you zoom in and out. There seems to be a bit of flashing in the exposure, and it seems to get somewhat brighter when you zoom in and somewhat darker when you zoom out. But it's the flashing that is more noticeable to viewers during the zoom, even though it's locked at f11 the whole time. What do you think?
 
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Okay thanks. But since I don't want any orange in the image in post, what's the point of setting it to daylight, if all you are going to get is orange? If I want the dusk to be white in the final product, then why set it to daylight, if you do not want orange for your look to begin with?
 
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Well, because when I shoot at dusk it is because I want it to look like dusk.... otherwise I should shoot at an other moment.
But if I need it to be white I use a graycard to set white balance and then I shoot it as well for reference.

If your intention was to make it white, I guess you overdone it, since it is all blue...
 
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WalterB said:
Well, because when I shoot at dusk it is because I want it to look like dusk.... otherwise I should shoot at an other moment.
But if I need it to be white I use a graycard to set white balance and then I shoot it as well for reference.

If your intention was to make it white, I guess you overdone it, since it is all blue...
Click to expand...

Okay thanks. But what if I want the blue dusk look like some movies have? How do I get the blue dusk, if I must shoot at a daylight balance, which makes dusk orange?
 
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harmonica44 said:
Okay thanks. How do I get that blue dusk look like some movies have without it looking so bad. Any ideas?
Click to expand...

You should do all your color correction in post. White balance your original footage correctly so all the colors are natural, then you can add blue hues later on in premiere or after effects or whatever you're using. Just do a youtube search for day for night color correction and you can find a ton of good stuff.
 
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Okay thanks. It's easy to add blue hues, when the light is white to begin with. But if I shoot with the daylight balance setting, the dusk is orange, and if I get rid of the orange in post, there is more noise, compared to white balancing the orange, originally.

I guess I just find it harder to work with "correcting it in post", as oppose to getting it closer while shooting to begin with, and getting less noise as a result.
 
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Look, observe and think H44.
Have you never watched the sun set with your other half?

The blue look can be acquired just after the sun has set.
Then there is still light, but everything is in the shadow of the earth.
The orange light is gone and if you look to the east the sky is already getting darker blue.
Where the sun set the sky is bright than on the opposite side: you can use this to have character stand out a little bit against the blue sky, since there is still some ambient, shadowless light coming from where the sun has gone.

(And if you want that look for longer scenes, you can consider overcast days, where the sunlight is diffused so much it cast no real shadows and make it look blue. (You can white balance true an orange gel. 1/4, 1/2 or full daylight to tungsten gel, depending on the blueness you want.) )

However, depending on the weather, if you look to the west there might still be some pink/purple/orange clouds on the horizon.

Trying to get that blue look in a blazing orange setting sun is silly.


The opening of this video was shot right after the sun had set with WB set to daylight. In post I added a little bit of blue and a gradient to darken the sky a little bit (with Colorista: in 2010 already a great plugin). There is also a shot shot during sunset where you see a pink/orange sky.
https://www.youtube.com/watch?v=qeGqRVkE0AE
 
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I suspect why your exposure is changing is because you have a variable aperture lens. It's probably the one that came with your camera and it's speed is listed as something like f3.5-5.6. That means that as you zoom out, the efficiency of how the lens passes light through changes. This is common with all low end still zoom lenses. You could get a fixed aperture lens but it will be much bigger, generally, and you can add a zero to the price.

As far as the color issues, there are a lot of factors at play. As an old film guy, I don't necessarily believe you should just hope to do everything in post (not that films aren't graded, of course), but you can do a lot in camera. With video, it wasn't uncommon for DP's to carry around large swatch books of filters (weren't these called gorilla books) and to white balance through them to achieve a particular look. However, as other people have said here, your best bet is to shoot at dusk when the sun is below the horizon. Problem with that is you will have very little time. If it's one shot your okay, a whole sequence, not so good. You essentially don't want the sun in your shot, you won't be able to make that work without a budget. So you could shoot away from the sun around dusk and get a little more shooting time.

If you had an overcast day, you might be able to mess with white-balance, under-expose and shoot with a much bigger time window. For that I would shoot tungsten balanced, and if that's too blue, put quarter or half CTB in front of the lens before you white balance.

The shot you posted has lots of problems. Namely, you're shooting into the sun, which is way above the exposure shoulder and will never look like dusk. I would wager you would get okay result doing exactly what you did, only shoot away from the sun, under-expose some, and desaturate in post. The sky might still be a problem, but it would look a lot better. I've done similar things myself and it came out fine.

I'm not sure what time of day you shot your clip, but if you're trying to pull off a day-for-dusk effect, the sky will always kill it.
 
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