vignetting with nikon lenses

B

bradywurtz

Active member
ok, so i have the letus mini for my panasonic hmc-40. i have a 50mm which works great, there is virtually no vignetting when i'm using it with the aperture opened all the way (1.8 f stops). but once i start to slow dow the f stops to something like 2.8 or 4, it starts to vignette. the corners of the screen will become darker as the very center of my screen remains just as bright as it would be if i left it open all the way.

is this normal? i know it doesn't do this when i have the lenses attached to my Nikon FE photography camera, but i didn't know if maybe lenses work different when working on a 35mm adaptor for a video camera as compared to using it on a SLR camera
 
on my hmc-40 it says i'm at 58 for zoom. i only zoom in just far enough to fill up the screen from the letus, i don't zoom in any further than i have to
 
whoa no, i don't want to do that, i'm going to zoom to far into the adaptor on the letus. i've tried zooming in further than what i need to, and it's not good. you want to stay away from zooming in any further than you have to.

i just want to know, does anyone else have this problem with using lenses on their letus adaptor or other 35mm adaptors?
 
Bradywurtz, you asked a question and Kodjo answered it correctly. Just because you filled the frame, does not mean that it is even academy framing or true 35mm photography framing. You can get a much wider field of view with a particular lens on an adaptor than is possible on a true 35mm camera. This extra wideness you are experiencing is at the expense of edge to edge sharpness and vignette-ing. Its very normal for a wide lens to vignette, and the severity of the vignette (and E2E sharpness) will vary with f-stop.

Do a search on academy framing - there is a neat trick to verify academy framing using an 8.5x11 piece of paper.

The bottom line is, if you want to avoid vignette, zoom in to at least true 35mm framing. If the field of view is not wide enough, you will need a wider lens. Vignette seems to be least forgiving on wide lenses.

BTW - i have an Extreme and 24, 50, 85, 135 and 200mm Nikkor primes.

Jason
 
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does the vignetting happen much when using something like the 50mm prime? cause i originally said i was using a 50mm prime, not a wide angle lens. i never mentioned using a wide angled lens.

my issue is that when i'm using just my plain 50mm prime lens, i feel like i can never go further than 4 f stops without making the video look dark everywhere except the center, that seems extremely over exposed.

i feel like when using my prime lenses on my letus, i need to use an ND filter on the lens to prevent over exposure. because if i even try to use the aperture on the lens, i get the slower f stop effect on the whole image except for the center of it

am i explaining this right? if not let me know, i have a hard time explaining things sometimes. i may try and upload some screen shots if i can soon
 
http://www.youtube.com/watch?v=phngqOc2JA0

ok, so here is a video of what i'm talking about. i just uploaded it on youtube. as you can see, once i start stopping down on the f stops, the center stays bright as the surrounding sides darken closer and closer toward the center.

this is with stopping down the aperture on my lens, not on my camera.

if i stop down on my aperture on my camera, it is evenly darkened across the whole screen, but when i do this from my lens it seems to just slowly darken only the corners.

is this normal? and if so, i'm assuming that everyone who uses a 35mm adaptor for their video cameras do not adjust the aperture on their lenses. is this right?

it just seems like if i used the aperture on my lens, i'm only going to darken the image along the sides of my video, and not evenly throughout the whole video
 
Whta you are describing does not appear to be a Letus problem. If anything, your lens or camera may have a problem. Try a different lens to make sure.
 
Actually Bradywurtz, the vignetting is there the whole time. I bet if you took screen grabs of 1.8 and dropped the luminance to the level it is at f4, you would see the same image.

As JD stated, some lenses vignette worse than others. If your 50mm is the problem, use a 35mm and zoom past the vignette. Problem solved - no vignette, no change in field of view.

The good news is that your sensor seems to be lined up with the adaptor GG fairly well. At least your vignette is centered. Mine is off center by about 15%. Ocasionally I will use the vignette on a 24mm nikkor for effect. Most of the time I zoom into academy framing.

Jason
 
but if i zoom past the vignette, i don't understand how that solves the problem, because then i have two bigger problems. i would have zoomed in further on the GG on my adaptor, so the grain is now more noticeable, and i've also zoomed in further so it no longer looks like i'm using a 50mm, it looks like i'm using a more zoomed in mm lens, like a 70mm or something (if that number lens exists)

how would zooming in more on my GG make no change in field of view?

i'm sorry, i'm not trying to sound like i'm attacking or anything cause i'm not, i'm just extremely confused
 
bradywurtz said:
but if i zoom past the vignette, i don't understand how that solves the problem, because then i have two bigger problems. i would have zoomed in further on the GG on my adaptor, so the grain is now more noticeable, and i've also zoomed in further so it no longer looks like i'm using a 50mm, it looks like i'm using a more zoomed in mm lens, like a 70mm or something (if that number lens exists)

how would zooming in more on my GG make no change in field of view?

i'm sorry, i'm not trying to sound like i'm attacking or anything cause i'm not, i'm just extremely confused
Click to expand...

Yeah everyone is correct, you need to zoom in to the gg at around 70%, when I had my Letus I had to go all the way to 75-78 or so.

Theres so many variables in this game but Ill try to give my input.

Check out this chart:
http://www.hotrodcameras.com/wp-content/uploads/2009/06/sensor-size-chart-web2.jpg

See the size of the 5D Mark II sensor? Thats the sensor size the lens you're using is made for.

Then have a look at the S35 sensor size? That's the sensor size the adapter you're using is emulating. So in essense what you're getting is a crop ratio.

A full frame photography 50mm lens will indeed look like approximately 70mm lens when used in S35 format camera. It's much like using these lenses on a Canon 7D or a Panasonic GH1 although their crop ratio is more like 1.6 to 2. A 50mm full frame lens on a GH1 will crop the image to make it look like a 100mm lens.

Sami
 
"you need to zoom in to the gg at around 70%"

i'm using the Panasonic HMC-40. Should I still zoom into 70%? I didn't know if it was different depending on what camera you're using

also, zooming in that far, will i or will i not get a lot of visible grain from the adaptor? Letus's website specifically told me just to zoom in just far enough to fill in the screen, are they wrong?
 
bradywurtz said:
"you need to zoom in to the gg at around 70%"

i'm using the Panasonic HMC-40. Should I still zoom into 70%? I didn't know if it was different depending on what camera you're using

also, zooming in that far, will i or will i not get a lot of visible grain from the adaptor? Letus's website specifically told me just to zoom in just far enough to fill in the screen, are they wrong?
Click to expand...

Im not familiar with that camera so I cant say, but yes it is slightly different depending on the camera and also the still lens you're using. The wider the lens the further you need to zoom in to avoid vignette.

When I purcased my Letus Extreme and used it with my EX1 I had the exact same problems you are having now and had to email with Letus for a long time to understand how the adapter really works. The Letus website is not very helpful in regards to mentioning the problems and drawbacks of the system.

One more thing, never stop down past f4 or 5.6 with your still lenses when using them with the adaptor, you will see grain. I also found that the camera itself is best somewhere around f1.9 to f5.6. So if you shoot outdoors use ND filters.

I was able to zoom in fully to the adaptor without any noticable difference in the grain. So I was able to use the zoom range from 75% to 100% on my EX1.

Sami
 
Yea, my wide angled lense does vignette more than my 50mm.

i put my camera on a tripod and locked it down, put my 50mm on, zoomed in to fill the screen with the GG and zoomed in as far as i had to to get rid of the vignetting at f/2.8.

then i added my wide angled lense, zoomed in to fill the screen with teh GG and zoomed in as far as i had to to get rid of the vignetting at f/2.8.

after doing so, looking at both clips, they look exactly the same! i had to zoom in so far with my wide lens that it pretty much looks just like my 50mm!

what is going on!? it seems like buying a wide angled lens is irrelevant, and i don't understand why any person would want to buy a wide angled lens for a letus adaptor, because it's going to look exactly like the 50mm!

i just feel so confused and frustrated at this thing. it seems like using a letus adaptor is only good if i just use a 50mm prime. every other lens now just seems like a waste of time because they're all going to either look like the 50mm when i zoom past the vignetting, or i could just zoom in on the GG further to make it look like a 200mm lens

this obviously can not be right, i feel like i'm the only person in the world who has figured this out, so i have to be wrong
 
bradywurtz said:
does the vignetting happen much when using something like the 50mm prime? cause i originally said i was using a 50mm prime, not a wide angle lens. i never mentioned using a wide angled lens.

my issue is that when i'm using just my plain 50mm prime lens, i feel like i can never go further than 4 f stops without making the video look dark everywhere except the center, that seems extremely over exposed.

i feel like when using my prime lenses on my letus, i need to use an ND filter on the lens to prevent over exposure. because if i even try to use the aperture on the lens, i get the slower f stop effect on the whole image except for the center of it

am i explaining this right? if not let me know, i have a hard time explaining things sometimes. i may try and upload some screen shots if i can soon
Click to expand...

You should calm down and read properly what they are explaining to you. This is NORMAL for any lens. You are using a setup that is not meant to go past F4. This is for any lens. You should be zooming into the academy size frame to eliminate most of the problem.

This also depends on the lenses you use. There are many different build qualities for lenses. There are many different 50mm lenses too, even NIKKOR 50mm lens's are different from decade to decade.

I see no problem in the footage posted. You should not be stopping down the lens, If you want to make the image darker you need to add a neutral density filter in front.
 
I totally understand your frustration, I was there. But dont worry. As soon as you get the hang of it kinda so to speak you'll be happy, I'm certain :)

Try and go out and shoot something in proper light. Looking at your youtube video I dont think theres anything wrong with the letus, nor your cam or the lens. It looks exatly as I would expect if youre not zoomed in enough and are in low light situation. If you're shooting in low light you will also see more vignette. I also suggest you get a little faster wide lens, you can get nice 24mm f2 lenses for pretty cheap.

Just for the sake of it zoom to 80% with your camera, shoot tests in proper lighting with both your lenses (dont adjust zoom, keep at 80%) and post screenshots here.

Sami
 
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