Iris problem?

J

jrnyfan@nc.rr.com

New member
So I've only been using the HMC-150 for about a week now. When I'm shooting outdoors and set control to automatic, my picture is way over exposed. When I swap over to manual, I can close the iris - but when it gets to F-11, the picture is still terribly over exposed; and of course, the next step is fully closed (black).

If I turn on the ND Filter I can get acceptable images. But I guess my question is - is it normal to HAVE to have the ND filter on outside or have I accidentally altered some setting (or worse, have a defective iris or something?)

Any info/advice would be appreciated by this newbie!

(And yes, I have ordered "the book.")
 
they put those ND filters on there for a reason....you have finally found the reason.
use them and be happy the camera does as well as it does in low light. ;)
also, in outdoor scenes with high contrast, you will never be able to get all objects in the frame exposed perfectly. i set the exposure for the subject in the shot even if this means that the highlights are blown out in that patch of sun behind them. video cameras have a limited dynamic range and you will always be making a compromise.....that's why filmmakers take so much time to light a scene; to even out the contrast so that the camera can see everything.
 
Thank you thank you! Just wanted to make sure it wasn't operator error. I really am impressed with what it does indoors in low light. I just felt like somehow I was deteriorating the image by turning the ND filter on, but as long as it's not, then I'm a happy camper.
 
I'm a newbie too and I'm glad you made this post because I had the same concern with the overexposure.

I have been struggling to get a good image with contrast. I hate turning on ND filter even if it is suggested by the camera. Contrast is lost. Black looks gray (foggy look).

As you stated, I switch to manual iris. With the help of zebra, I try to reduce the overexposure region. i noticed if I select scene settings "SPARKS" , the image looks better.

As a newbie, I found the Panasonic scene settings very interesting. I purchased recently Barry's book, i'm still reading it.

To be honest, I haven't figured out all these settings. for instance, for me , reducing the MASTER PED as the same effect as either setting the KNEE to LOW or GAMMA to (LOW / B-PRESS). It makes the picture image sharper :)

DRS setting is always grayed out??? I could not figured out why??

My 2 cents suggestion is to spend time and play a lot with the settings. It will take time to master the HMC150. This camcorder has great built in features such as the focus assistant and waveform/color vector graph. Once we understand what setting do and how to use it properly based on the light condition , I'm sure it is gonna make us happy :)

This week end, I went to the beach where light is strong. I got overexposure. I used different settings on the same shot. I wrote down my settings and when I came back home and checked my shots with my Sony Vegas 9 editing tool .... I had a better idea about what settings to tweak next time If I face the same overexposure dilemma :)
 
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hattia said:
I have been struggling to get a good image with contrast. I hate turning on ND filter even if it is suggested by the camera. Contrast is lost. Black looks gray (foggy look).
Click to expand...

ND does nothing to contrast or color, it only lowers the amount of light hitting the lens.

hattia said:
DRS setting is always grayed out??? I could not figured out why??
Click to expand...

DRS only works when shooting 60 fps, either interlaced or progressive
 
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Someone once explained ND filters to me as "sunglasses for your camera lens".

What I like about the ND filters is that it allows you to open your iris back up as wide as you like, which in turn gives you a shallower depth of field which looks a bit more cinematic.
 
TigerFX said:
Someone once explained ND filters to me as "sunglasses for your camera lens".

What I like about the ND filters is that it allows you to open your iris back up as wide as you like, which in turn gives you a shallower depth of field which looks a bit more cinematic.
Click to expand...

interesting. I might be mistaken but I think I tried that. I had overexposure and the camera suggested to select filter 1/4 ND. I opened the iris...and the camera suggested to select filter 1/16 ND :)
 
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KKeller said:
ND does nothing to contrast or color, it only lowers the amount of light hitting the lens.



DRS only works when shooting 60 fps, either interlaced or progressive
Click to expand...

yes indeed i just read this this morning page 53 of Barry's book :)
 
hattia said:
interesting. I might be mistaken but I think I tried that. I had overexposure and the camera suggested to select filter 1/4 ND. I opened the iris...and the camera suggested to select filter 1/16 ND :)
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Yup. I love it when that happens. Also for what it's worth I think Barry said around F4 is a sweet spot so aim for that when you can.

It's really nice we have three integrated ND filters. The old SD prosumer cameras typically had one, and two for the fancy cameras. Having three is such a blessing.
 
TigerFX said:
Yup. I love it when that happens. Also for what it's worth I think Barry said around F4 is a sweet spot so aim for that when you can.
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What do u mean by F4?

it is that we should always select filter 1/4 ND (when required )and change other settings (increase iris, tweak Knee, gamma curve...) to get the right exposure and sharpest image?

PS : i watched your video http://www.vimeo.com/9368376 . Nice PQ. I would not mind to know what was the settings you used (record format and scene settings)

thanks
 
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Thanks. F4 Is the exposure/apateure/iris setting, measure in f-stops (lower is brighter). F4 is near the middle, which makes sense that there would be a sweet spot there.

Thanks for your feedback - I shot it in 720/24p (could have used 1080/24p but I was worried about the performance hit to my laptop and knew I was doing web-only distribution) and exclusively used Barry Green's LoNoiz scene file. I like the idea of low noise and the fact that it's a very neutral scene file. It doesn't try too hard to push the contrast and left me latitude in post. In relaity, the only color work I did was Premiere's RGB curves tool to patch the white balance in a few areas and push the gamma (the center of the curve) to brighten up some of the darker shots.
 
With respect this is not the sort of camera that I would recommend for a beginner but f4 refers to the aperture setting, which in basic terms is the size of the hole letting light into the camera.

You should not be touching any of the scene file setting just to get the exposure correct. It is a function of the shutter speed aperture and natural density filter. Although some of the scene file settings do to some extent change the brightness of the picture slightly they are not there to control exposure. The exception is the A IRIS LEVEL in the scene file menu which allows you to the set the auto iris to under or over expose.

I suggest you switch the iris to auto and set the ND filter to what the camera recommends and all then switch back to manual iris to fine tune.

1/4 HD tells you the amount by which the filter is reducing the light entering the camera. One f stop is the same as half the light and two f stops is 1/4 of the light so HD 1/4 reduces the light by 2 stops.

Ken
 
Thank you Allen and Ken,

I'm still confused about the definition of f-stop. Yes, I'm a beginner but I do believe the learning curve for this camera is not too steep :)

so if someone says "use aperture F4" it means I must set my filter to ND 1 /8 ?

What I miss reading Barry's book is some good real situation example. For instance, what would be the rights steps to fix an overexposure?

Let's say, I'm shooting a landscape. Sky is cloudy. Light is bright. I face overexposure. what i have in mind after your recommendations:

1) swith iris to auto mode. let the camera adjust it.
2) select the suggested ND filter
3) switch back to manual iris mode
4) try to tune up by opening up the iris. Use zebra features.

Now I might need to tweak some scene settings. For instance, i would like to see the details of the clouds. Panasonic scene settings manual recommends to set "KNEE" to "LOW".


-herve
 
If you use an aperture of say f4 the ND filter setting will depend on how bright the light is. ND 1/8 is three stops less light the same as going from f4 down to f11.

f stops are a progression where each one lets in half the light as the previous one with the larger the number the less light. i.e. f1.4, f2, f2.4, f4, f5.6, f8 anf f11

Google photography aperture and you will learn what the f numbers mean.

Your 4 steps based upon my suggestions are correct as a starting point to learn.

The most comprehensive information on scene files is Barry's book, which you have. Also read the sections on Zebra and waveform monitor to get your exposures spot on.



I hope this helps,

Ken
 
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Yes sorry I was in a hurry as I am off to Poland tomorrow and am getting ready at the same time.

I could not believe I typed that as I have taught this stuff to camera clubs for years. It must be old age getting the better of me.

I have corrected my post.

Ken
 
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hattia said:
Thank you Allen and Ken,

I'm still confused about the definition of f-stop. Yes, I'm a beginner but I do believe the learning curve for this camera is not too steep :)

so if someone says "use aperture F4" it means I must set my filter to ND 1 /8 ?
Click to expand...

No no no ;)

Let me break it down - there are four ways you can effectively control the brightness:

1) Aperture/exposure/iris: the primary means of adjusting brightness. This is measured in F-stops, with F1.5 or so being the brightest, F4 is a nice medium, and F11 is the darkest it can go. Adjusting this physically opens a 'door' (the 'iris' is it's name) which allows more or less light to hit the sensor. A very gradual adjustment, you can change it while shooting gracefully.
As a side-note, the wider, aka, brighter the F-stop, the shallower your depth of field.

2) Shutter speed: measured in fractions of a second. This is a measure of how long the iris stays open for. The longer it stays open, the more light gets through. A typical setting is 1/60, which means it opens for 1/60th of a second. That makes sense shooting at 60fps.
If you cut the time in half (down to 1/120th) then your picture darkens by half. The main reason you'd do this is to reduce motion blur. If you're shooting fast action and especially if you plan to go to slow motion, knocking this down to 1/120th or faster is a great idea. IMO this tends to give it a "Jason Borne dodging bullets" or "Saving Private Ryan" action-movie feel, a fairly new and novel look since most cinema is traditionally shot at 1/48th. I almost always leave my shutter at 1/60 because I like how that motion blur is similar to what our eyes see. Avoid changing this during shooting because it's very abrupt.

3) Neutral density filters
On a bright day sometimes the exposure control isn't enough, and even the darkest F11 will be way too bright. Just slap on an ND filter and you're good to go. Avoid changing this during shooting because it's so abrupt.

4) Gain
If you're shooting in low light and everything else is set to brightest, this is your last resort. Only use this when you need it, because it introduces ugly grain into your footage. The HMC though is very good about low noise - even small amounts like 3 or 6db can wreak havoc on similar cameras; my experience is that the HMC150 copes quite well. These are set as "low / medium / high" on the side of your camera, and you can choose in the menu what values these correspond with, from 3db to 12db. If you need 18db (looks like the Blair Witch Project) there's a menu setting to set that to any user key.

Let's say, I'm shooting a landscape. Sky is cloudy. Light is bright. I face overexposure. what i have in mind after your recommendations:

1) swith iris to auto mode. let the camera adjust it.
2) select the suggested ND filter
3) switch back to manual iris mode
4) try to tune up by opening up the iris. Use zebra features.

Now I might need to tweak some scene settings. For instance, i would like to see the details of the clouds. Panasonic scene settings manual recommends to set "KNEE" to "LOW".


-herve
Click to expand...

My personal formula is this:

1) Decide what's more important to me: a specific depth of field (shallow for 'beauty' shots, wide for landscapes), or a specific motion blur (1/60 for everyday/smooth, 1/120 or more for action/shaky). Once I've made this decision, I set that. So if it's shallow DOF I'm after, I'll open up the iris as wide as I can.

2) Fix the brightness using all the other tools at my disposal

The other consideration is, is there a chance the lights will darken (will the clouds cover the sun)? If so I don't want the iris open the whole way because the only way to brighten the picture would be to shut off one of the ND filter's, which is very jarring to viewers.

In all practicality what I really do is just set my shutter to 1/60 or 1/120 where I like it, then set the iris to a comfortable medium so I have room to twiddle if lighting changes (F2-F6ish), and if things are too bright/dark, I use ND filters/gain to compensate before I start rolling.



By the way, I don't touch scene files at all. I know, I'm missing out on a lot, but there are SO MANY and I haven't taken the time to stare at the difference on a monitor and I'm too cheap to buy Barry's book (though I know it's wonderful). My experiences with making scene files is that I can make it look awesome for any given shot, but when I move the camera to a different environment my beautiful look gets trashed. Because of that, I choose to play it safe and use LoNoiz for everything, and control things in post. I see a TON of discussion about scene files but I tend to stay out of it, leave things toward the middle and if I want to play with it in post, I can. I've already ruined a bunch of fine shots by using a scene with too much contrast, and I don't want to make that mistake again. The LCD is not trustworthy for these sorts of details.
 
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hattia said:
you meant the opposite ?

as per this document http://www.mir.com.my/rb/photography/fototech/apershutter/aperture.htm

the smaller the f-stop (e.g 1.4) is , the larger is it the aperture. Thus allowing more light.

-herve
Click to expand...

The confusion here is in how you're writing the f-stops. It is NOT, e.g., f2.8, it's f/2.8. As the denominator grows larger, the number grows smaller. Thus a larger f-stop (e.g., f/2.4 vs f/3.4) means a larger aperture; larger DENOMINATOR means a smaller number and a smaller aperture.

Just write 'em right and it makes sense.
 
Thank you Allen for taking the time to share your experience. It is very informative. I finished reading Barry's book. I wish I could find in it this type of advice. Don't get me wrong, Barry's book is great. More complete than the instructions manual.

Since you talked about DOF. Do you use any 35mn DOF adapter? If yes, which one you will recommend?

Now, let me know if I'm mistaken. If I understood correctly. In order to control the exposure for good brightness, we must do our best to keep the aperture close to F/4 and tweaks the shutter speed to let more light in.

I will definitely try the LONoize Barry's scene settings.

Thanks again.

-Herve
 
hattia said:
Since you talked about DOF. Do you use any 35mn DOF adapter? If yes, which one you will recommend?
Click to expand...

No, I'd love one but they're too darn expensive. For half the price you can get 35mm DOF in a DSLR (the Canon T2i) which gives you a second camera to boot. I've got my eye on that. Not to mention 35mm adapters take a while to setup and require some extra support because they're very front-heavy.

Now, let me know if I'm mistaken. If I understood correctly. In order to control the exposure for good brightness, we must do our best to keep the aperture close to F/4 and tweaks the shutter speed to let more light in.
Click to expand...

You can do what you like. Really the F/4 suggestion was just something to keep in mind, I'm not even sure how noticeable that "sweet spot" is. It's engineered to look pretty good at every f-stop.

Really you probably want to tweak the light during your shot with exposure because it's the gentlest. If you depend on switching the ND's or shutter during the shoot, it will be a very abrupt shift. So before you're rolling, try to get your exposure near the middle so you have wiggle room both ways.

All of these are suggestions anyway. Just get out there and start playing with it and you'll pick these things up ;). Don't worry too much about perfectly optimizing every setting - those sorts of tweaks (like finding the "sweet spot") are really only noticable if you're pixel peeping and other concerns like having a good tripod, enough light, things in focus, a good story, etc, trump these concerns of "perfect" settings by 10,000% easily.
 
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