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Metering on set procedure: choosing a correct ISO


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Hallo everybody,

I am introducing myself on "metering" world... :blink:

 

Reading some articles on web, I found this the should be pretty good to start:

 

http://www.sekonic.com/germany/whatisyourspecialty/cinevideo/articles/cine-essentials-scouting-a-location.aspx

 

I have a Sekonic L-308DC (I always wogk with DSRL or Digital cameras, unfortunately not with film stock).

 

Many article suggest to make a Lighting location scouting to measure the lighting of the stage: in short, to measure the light intensity of the light sources present in the location. In daily outdoor locations we can measure the natural light sources (sun) intensity in the moment we intend to film the scene. In outdoor night locations we can measure the natural light sources ( moon.... fires, candles, bonfires... ) or artificial lighting (street lighting, urban lighting....).

 

The problem is to set up a right ISO mode. We should be know which ISO value we (or the DP) intend/s to use for that scenes.

But how we can decide it and when?

I mean, when we (or the DP) are/is on location, we/he have/has to decide which will be the ISO value?

I know we should be remain always in a value from 100 ISO to 320 for Daily outdoor scenes, and at most up to 800 ISO, for indoor and night scenes to avoid noise. Of course, we needs light, we have to add instead to increasing ISO value.

So, are these the basic rules to choose the correct ISO value to use?

 

Many thanks for a reply! :)

 

 

 

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The cinematographer will measure the natural light levels on location during a scout knowing what the fastest stop of the lens they will be using and if they want to shoot wide-open.

 

But let's say you scout a location and it says you need to shoot at f/2.0 (if that's what you are limited to) at 3200 ISO and you plan on limiting yourself to 800 ISO.

 

You either have to add 2 more stops of light or get an f/1.4 lens and add one more stop of light, or compromise and shoot at f/2.0 at 1600 ISO. You may decide to cheat a little and open the shutter from 180 degrees to 240 or 270 degrees if shooting digitally.

 

But in terms of how the ISO looks, that's a matter of testing and looking at the results on as large a screen that you plan on presenting in. And it would also help if you played with the image in color-correction to see how fast it falls apart.

 

Also, keep in mind that you don't necessarily have to increase all the light everywhere, you might decide just to boost it in one area and let the rest play a little underexpose.

 

It helps if you take a few photos at the f-stop and ISO you'd like to shoot at -- let's say that is f/2.0 at 800 ISO -- so you see what the space looks like even if it is underexposed. You may decide it looks fine darker and all you need is a little more light on the faces in one area, or just need to boost one source a little more but the rest are fine. That's the job of previsualization when the cinematographer imagines what the space will look like as different lights are added, adjusted, or even turned off.

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The cinematographer will measure the natural light levels on location during a scout knowing what the fastest stop of the lens they will be using and if they want to shoot wide-open.

Okay, but the problem is you are going to use many lenses... for example, in a scene indoor, you can use a wide lens for the Establishment shot (Master shot) (i.e. 24mm or a 35mm) and than you use a 50mm, 85mm, 100mm or/and 135 mm for the Coverage. And every lens has a different f/ stop...

So, if I have rightly understand, you have to scout you location referring your brightest lens you are going to shot (normally is a wide lens as a 24 or a 35mm). For example, I have a Canon 15-55 f/2,8, so I have to set up my meter to f/ 2,8 as aperture and than provide to measure natural source lights trying to use a good compromise about ISO value?

 

 

But let's say you scout a location and it says you need to shoot at f/2.0 (if that's what you are limited to) at 3200 ISO and you plan on limiting yourself to 800 ISO.

I don't understand this step: if you want to measure the natural light levels on location you have to set up ISO value

 

You either have to add 2 more stops of light or get an f/1.4 lens and add one more stop of light, or compromise and shoot at f/2.0 at 1600 ISO. You may decide to cheat a little and open the shutter from 180 degrees to 240 or 270 degrees if shooting digitally.

 

But in terms of how the ISO looks, that's a matter of testing and looking at the results on as large a screen that you plan on presenting in. And it would also help if you played with the image in color-correction to see how fast it falls apart.

 

Also, keep in mind that you don't necessarily have to increase all the light everywhere, you might decide just to boost it in one area and let the rest play a little underexpose.

 

It helps if you take a few photos at the f-stop and ISO you'd like to shoot at -- let's say that is f/2.0 at 800 ISO -- so you see what the space looks like even if it is underexposed. You may decide it looks fine darker and all you need is a little more light on the faces in one area, or just need to boost one source a little more but the rest are fine. That's the job of previsualization when the cinematographer imagines what the space will look like as different lights are added, adjusted, or even turned off.

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Also, keep in mind that you don't necessarily have to increase all the light everywhere, you might decide just to boost it in one area and let the rest play a little underexpose.

 

That's exactly what I see in a lot of student films, these days. Filmmakers feel that they need to light the entire space, often creating an uninteresting frame. I know cameras have high-dynamic range today, but it's always refeshing to see someone who knows how to play with extreme over or underexposure, creating nice color-contrast.

 

So as David said, don't be afraid to experiment with different lighting styles.

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Hallo guys,

yes this is what I look for when i try to create a lighting: isolate what is important. So, let's light what you need...

So , think you should find

 

 

The cinematographer will measure the natural light levels on location during a scout knowing what the fastest stop of the lens they will be using and if they want to shoot wide-open.

 

Okay, but the problem is you are going to use many lenses... for example, in a scene indoor, you can use a wide lens for the Establishment shot (Master shot) (i.e. 24mm or a 35mm) and than you use a 50mm, 85mm, 100mm or/and 135 mm for the Coverage. And every lens has a different f/ stop...

 

So, if I have rightly understand, you have to scout you location referring your brightest lens you are going to shot (normally is a wide lens as a 24 or a 35mm). For example, I have a Canon 15-55 f/2,8, so I have to set up my meter to f/ 2,8 as aperture and than provide to measure natural source lights trying to use a good compromise about ISO value?

 

 

But let's say you scout a location and it says you need to shoot at f/2.0 (if that's what you are limited to) at 3200 ISO and you plan on limiting yourself to 800 ISO.

I don't understand this step: if you want to measure the natural light levels on location you have to set up ISO value

 

You either have to add 2 more stops of light or get an f/1.4 lens and add one more stop of light, or compromise and shoot at f/2.0 at 1600 ISO. You may decide to cheat a little and open the shutter from 180 degrees to 240 or 270 degrees if shooting digitally.

 

But in terms of how the ISO looks, that's a matter of testing and looking at the results on as large a screen that you plan on presenting in. And it would also help if you played with the image in color-correction to see how fast it falls apart.

 

Also, keep in mind that you don't necessarily have to increase all the light everywhere, you might decide just to boost it in one area and let the rest play a little underexpose.

 

It helps if you take a few photos at the f-stop and ISO you'd like to shoot at -- let's say that is f/2.0 at 800 ISO -- so you see what the space looks like even if it is underexposed. You may decide it looks fine darker and all you need is a little more light on the faces in one area, or just need to boost one source a little more but the rest are fine. That's the job of previsualization when the cinematographer imagines what the space will look like as different lights are added, adjusted, or even turned off.

 

 

I David, I forgot I forgot to highlight text with my considerations... I make it here above:

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I don't know why I can not edit my message... :angry:

 

Anyway, I try to write again what I wanted to say:

 

As I said, the first approach should be to isolate (light) what is important for you (for the script, for the scene, for the Director...), regardless of how it illuminated the scene originally. Okay.

 

But there are many cases (Docs, Historical, Turistic, ...) where you have to consider to PRESERVE the original on location lighting:

For example, if we are in a Church, or a Villa, or a Gallery or historical place or in every place who the lighting location has something special (authentic, original...) - we can meter the original lighting contrast ratio and preserve it, if we need to increase the brightness of the scene because we have little light lenses, for example.

Vice versa, another interesting aspect to check the original on location lighting - when it is too bright [as a DAY Outdoor scene, or DAY indoor scene with many windows or on site lighting sources (Offices, supermarket, ...)] - is to underexpose the scene to see better the contrast ratio of the original scene, evaluating if it could be great for your creative/narrative purposes.

 

Of course, when you shot an underexposed scene, you should use ND filters to preserve the possibility to choose the Aperture only for Depth of field (Soft or Deep focus).

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Of course, when you shot an underexposed scene, you should use ND filters to preserve the possibility to choose the Aperture only for Depth of field (Soft or Deep focus).

 

 

Do you mean over exposed..?..

Of course, over exposed!

 

(But the REAL problem here is I can not edit my messages... :unsure:)

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  • 3 months later...

Hallo everybody, this message posy is just little confused because it was not able to edit my replies....

For this reason, I still have some doubts that I would like to clarify.

 

If I am right, in film stock you have maximal ISO 500 (!). In Digital, instead, I read the best "standard" setting for ISO should be:

- outdoor, max 320 ISO;

- indoor, max 800 ISO.

That's to avoid to compromise image quality with a huge range of noise.

 

The second consideration is that we normally shouldn't shoot in "wide open", to avoid frequent out of focus, but we should choose a "practical" aperture...: i.e I read the most used aperture in cinema are f/4 and f/5.6. Anyway, we should stay around a range from f/4 up to f/11 and more (Greg Toland deep focus approach...).

 

Said that, I'd like to make a piratical example to understand if I got it... :unsure: : I have a Canon EF 17-55 with constant (fastest) aperture in f/2.8.

 

Outdoor, day, we shouldn't have problem to stay on ISO in a range of 100 up to 320, using a least an f/4 as aperture. Shortly, if you have much light, the have the only problem to limit it... (ND filters closed aperture...)

 

The problems come when we have low lights...

 

- Indoor, day, only natural lighting from windows, doors, and similar.

I start to set up the light meter to 800 ISO, 25fps, 180 as shutter angle: I have a f/1.4... so, it should mean I need to add 2 more stops of light, because I don't want to use open wide f/1.4 (even If I could have it) and because, of course I'd don't want an ISO value upper to 800.

 

This reasoning is correct?

 

 

Many thanks for a reply! :wub:

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Right off the top you make a statement that isn't correct about ISO... Where did you get the notion that all cameras have a 320 ISO outside but a 800 ISO inside? Why would it be different outside? Do you think digital cameras are less sensitive in daylight? Why do you think all cameras are designed the same way with the same sensitivities?

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The problems come when we have low lights...

 

- Indoor, day, only natural lighting from windows, doors, and similar.

I start to set up the light meter to 800 ISO, 25fps, 180 as shutter angle: I have a f/1.4... so, it should mean I need to add 2 more stops of light, because I don't want to use open wide f/1.4 (even If I could have it) and because, of course I'd don't want an ISO value upper to 800.

 

This reasoning is correct?

 

 

Yes, for you intention the reasoning is correct.

That is if you want to come to your lens' f2.8.

 

...

 

About the ISO's.

 

Your working ISO's, being Out or Indoors, should be the ones

you accept the picture quality off, noise wise.

 

So your above "100 ISO to 320 for Daily outdoor scenes, and

at most up to 800 ISO for indoor and night scenes"

is a relative thing.

 

You might still like the look of an 800 ISO image outdoors.

Or you decide to make the indoors/night shots pristine

clear so you light up the set to levels for say f4, ISO 100, 1/50.

 

Test your camera at various ISO's, decide what is optimal for you,

what will pass and what's unacceptable.

 

 

Same for F-stop.

While 1.4 sounds sexy and "useful" , test if it is really that practical having razor thin DoF

and how is the focus following working for you. Or you like/need the sharpness

when the same lens is stopped down at f4.

 

With those parameters you'll know where you at when doing meter readings.

 

 

Best

 

Igor

 

 

PS: You option for editing your post is available just a limited amount of time after adding the reply.

I think, just couple of minutes.

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Different cameras have different optimal ISO ratings, but it is mostly about choosing a compromise between noise and overexposure clipping -- low ISO ratings give you less noise but more clipping in overexposed areas, high ISO's give you more noise but more overexposure information.

 

So for outdoor shooting, it can be complicated because some people want a cleaner image while other people want more overexposure latitude.

 

For low-light photography, it all depends on your tolerance for noise.

 

Also, since most sensors prefer daylight-balance, when shooting in tungsten-balance the camera is basically pushing an underexposed blue channel to compensate so blue has the most noise in it. So your noise characteristics at high ISO's partly depend on the color balance -- you may, for example, think that under daylight-balanced lighting that the camera noise at 1600 ISO, is acceptable but too noisy under tungsten-balanced lighting.

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Right off the top you make a statement that isn't correct about ISO... Where did you get the notion that all cameras have a 320 ISO outside but a 800 ISO inside? Why would it be different outside? Do you think digital cameras are less sensitive in daylight? Why do you think all cameras are designed the same way with the same sensitivities?

Hi David,

every camera of course has different sensor sensibility, my example was a general approach for DSRL, but yes, it to much rough. We should test every camera in use to see which are the ISO limits. My general consideration was that in outdoor daily scene we have always more light then in indoor scene, so there is not reason to push up the ISO value.

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Yes, for you intention the reasoning is correct.

That is if you want to come to your lens' f2.8.

 

...

 

About the ISO's.

 

Your working ISO's, being Out or Indoors, should be the ones

you accept the picture quality off, noise wise.

 

So your above "100 ISO to 320 for Daily outdoor scenes, and

at most up to 800 ISO for indoor and night scenes"

is a relative thing.

 

You might still like the look of an 800 ISO image outdoors.

Or you decide to make the indoors/night shots pristine

clear so you light up the set to levels for say f4, ISO 100, 1/50.

 

Test your camera at various ISO's, decide what is optimal for you,

what will pass and what's unacceptable.

 

 

Same for F-stop.

While 1.4 sounds sexy and "useful" , test if it is really that practical having razor thin DoF

and how is the focus following working for you. Or you like/need the sharpness

when the same lens is stopped down at f4.

 

With those parameters you'll know where you at when doing meter readings.

 

 

Best

 

Igor

 

 

PS: You option for editing your post is available just a limited amount of time after adding the reply.

I think, just couple of minutes.

HI Igor, thanks for your reply.

 

yes, first, we have to test every single camera (sensor) in use to see how ISO value works, as David mentioned.

Than we could also decide if we want use an high ISO even if shouldn't be necessary, to noise footage. Or stay in a pretty clean image situation, as you said, "...to make the indoors/night shots pristine

clear so you light up the set to levels for say f4, ISO 100, 1/50...".

Again, my was a general approach for DSRL Canon I used. A rough approach...

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Different cameras have different optimal ISO ratings, but it is mostly about choosing a compromise between noise and overexposure clipping -- low ISO ratings give you less noise but more clipping in overexposed areas, high ISO's give you more noise but more overexposure information.

 

So for outdoor shooting, it can be complicated because some people want a cleaner image while other people want more overexposure latitude.

 

For low-light photography, it all depends on your tolerance for noise.

 

Also, since most sensors prefer daylight-balance, when shooting in tungsten-balance the camera is basically pushing an underexposed blue channel to compensate so blue has the most noise in it. So your noise characteristics at high ISO's partly depend on the color balance -- you may, for example, think that under daylight-balanced lighting that the camera noise at 1600 ISO, is acceptable but too noisy under tungsten-balanced lighting.

So David,

great, I didn't know this relation between ISO value and overexposure clipping.

Some considerations about it:

1 - if we shoot in Log, we already obtain a reasonable dynamic range even if we use a low ISO value..., and we can recover detail in the highlights in post production, but with a minimal noise impact. So, why increase ISO?

2 - there is tons of noise effects to add to a footage... but remove noise is a process many many more complicated, and it compromise always the footage quality.

3 - in my approach, as inexperienced cinematographer, I let me guide by "contrast" (I thing it's still the best school). It mean basically that, I have to decide what should be rightly exposed and what not, inside the image. I don't like recent low contrast "log" mood... s

Shortly, I don't prefer have details in highlights (with a noised footage...) rather then having detail in a focused area which is important, and in which I don't need noise.

 

Okay, we are talking about an aesthetic approach, where all should be possible, anyway, I tend to create a clear and contrasted images as general approach. If I need grain, I add it in post.

 

Many thanks for your reply!

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1 - if we shoot in Log, we already obtain a reasonable dynamic range even if we use a low ISO value..., and we can recover detail in the highlights in post production, but with a minimal noise impact. So, why increase ISO?

Duca, this is not exactly correct. Suppose you have a camera that can record 10 stops of exposure, at ISO 800. 5 stops above the middle level and five stops below.

At 400 ISO you have 4 stops above the middle and 6 stops below.

At 200 ISO you have 3 stops above the middle and 7 stops below.

At 100 ISO you have 2 stops above the middle and 8 stops below.

 

So now you're shooting a high contrast scene in the outdoors. For your preferred f-stop you need 100 ISO, but you'll clip a lot of highlights and even below highlights (only 2 stops are recorded above the middle value). The preferred choice would be to shoot at a high ISO, and add ND filters to get to your preferred f-stop. LOG recording does not allow one to retrieve data that has not been recorded in highlights when using a low ISO setting.

 

The reverse is also true for low light shooting with high ISO settings.

 

So, you must know the dynamic range of your camera, through testing or experience, and the dynamic range of your scene, to properly choose an ISO setting for your shot.

 

From my experience, with an Alexa for example, I rarely shoot day exterior scenes below ISO 800. Maybe 400 sometimes. Never 100.

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As Bruce says, ISO setting does affect your clip point. The simplest example is the Alexa (not all cameras behave the same way though) where there are 14-stops of dynamic range recorded in raw or log. At 800 ISO, there are seven stops above middle grey and seven stops below middle grey captured, but if you rate the camera at 400 ISO, then there are six stops above middle grey and eight stops below middle grey captured (you've taken away one stop of overexposure information and given it to the shadows instead). Of course, you could decide at 400 ISO to underexpose a stop to hold another stop of overexposure detail... but then you are effectively rating the camera at 800 ISO again.

 

Some cameras are a bit more complicated since they use internal noise reduction to try and extend usable shadow information at different ISO settings so it's a bit less linear.

 

With my Nikon DSLR, my approach is to use the 200 ISO setting when possible, expose for the highlights (i.e. generally underexpose in order to hold bright detail) and then play with the raw file to bring up the shadows or brightness in general. But this is partly because I think the "native" sensitivity of many still cameras is on the low side (below 320 ISO) but internal processing allows them to use high ISO settings with minimal noise. But with those DSLR's often you'll notice that the dynamic range is a bit more limited at the high ISO settings because they are adding contrast in order to mask noise problems or a lack of shadow detail.

 

Ultimately, it's probably better to recognize that ISO setting is somewhat of a nebulous concept in a digital camera -- it's more about picking a rating that gives you the combination or balance between noise in the shadows versus overexposure information that you can work with practically.

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As Bruce says, ISO setting does affect your clip point. The simplest example is the Alexa (not all cameras behave the same way though) where there are 14-stops of dynamic range recorded in raw or log. At 800 ISO, there are seven stops above middle grey and seven stops below middle grey captured, but if you rate the camera at 400 ISO, then there are six stops above middle grey and eight stops below middle grey captured (you've taken away one stop of overexposure information and given it to the shadows instead). Of course, you could decide at 400 ISO to underexpose a stop to hold another stop of overexposure detail... but then you are effectively rating the camera at 800 ISO again.

 

Some cameras are a bit more complicated since they use internal noise reduction to try and extend usable shadow information at different ISO settings so it's a bit less linear.

 

With my Nikon DSLR, my approach is to use the 200 ISO setting when possible, expose for the highlights (i.e. generally underexpose in order to hold bright detail) and then play with the raw file to bring up the shadows or brightness in general. But this is partly because I think the "native" sensitivity of many still cameras is on the low side (below 320 ISO) but internal processing allows them to use high ISO settings with minimal noise. But with those DSLR's often you'll notice that the dynamic range is a bit more limited at the high ISO settings because they are adding contrast in order to mask noise problems or a lack of shadow detail.

 

Ultimately, it's probably better to recognize that ISO setting is somewhat of a nebulous concept in a digital camera -- it's more about picking a rating that gives you the combination or balance between noise in the shadows versus overexposure information that you can work with practically.

On my Canon DSLR (for still images) it seems to amplify the signal when raising the ISO setting, before writing the raw data. So, raising the ISO in this case does not increase dynamic range in the highlights at all. Actually, it feels like it lowers the dynamic range... So, if I shoot at ISO 200, I don't loose highlights that I might have captured at ISO 800. ISO 800 on my camera just looks more noisey :) So, on my Canon 5D, to capture more highlights, I need to expose less, and see a dark preview... Just as David observed on his Nikon.

 

I don't know about the Canon cinema cameras though. But it might be the same there, making ISO setting at different strategy than on an Alexa or Red camera. Does anyone who's used the Canon cinema cameras know how they work regarding ISO setting? I'd like to know, thanks!

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Dont know about the Canon.. but the Sony F5/55 has a tricky variant re ISO settings.. in Cine EI mode.. the camera will always record at the "native "settings.. ISO 1250 for F55 and ISO 2000 for the F5.. regardless of what you set the camera to.. the underlying recording ISO will be set in stone.. apparently Sony do this to maintain the highest DR off the sensor.. and its also why you have only the 3 preset WB choices too.. you can of course set the camera or your metre to any ISO..many people purposely over expose 1 stop to get better SN .. but you will need off set LUTs.. as the recorded footage will always be at native ISO..F55 1250 or F5 2000.. another tricky one.. in the menu,giving SDI out 1 and 2 a LUT will also record the LUT internally to your card.. 3 and 4 it wont.. it is clearly shown in the menu but thats been a common mistake ..

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Thanks Igor and David,

but for what above said, I should know how can I knew the camera used dynamic range, to apply our consideration...

So two, questions:

- how is the dynamic range of a camera (because many camera don't declare it in spec techs...)? Maybe a rough value, but usable...

- at which ISO value can I establish that I have (almost) equal stop above and below the grey middle value?

Sincerely I don't know how to answer to these questions..., but it crucial to test every used camera to know the specific dynamic range, and then apply the reasoning from Igor above.

The same problem about measuring (on set) the dynamic range of the scene - I mean scene already illuminated -. How to make it?

 

Many thanks for a reply!

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What camera do you have..? there should be somewhere the manufactures "native" ISO.. this will be the ISO ,as judged by the engineers of that camera ,that will give you the max DR equally between mid grey level..

 

I guess you could gauge the DR of a scene with a light meter .. or just by eye really.. if you are ext with a bright sky and area,s of deep shadow you have a high DR.. if you are in a big super market all evenly lit with hundreds of overhead florrie lights.. its not..

 

Maybe you are over thinking it.. I wouldn't use the ISO as an exposure tool, changing it ever set up.. if you use the native ISO ..for 99% of your shots you,ll be fine.. an Alexa at ISO800 is going to give you a good picture pretty much what ever.. F55 at 1250.. too.

Log gama is giving you so much head room you can usually afford to "rate " the camera one stop slower.. if you personally are worried about SNR of that camera.. so you raise that floor up on stop .. but I wouldn't lose sleep over it.. its not that the lowest possible ISO is going to give you the best picture..

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I have a Canon 60D, but anyway, what is important is to know how is the DR of the camera are you going to use, to be sure to apply a good ISO for that camera.

 

 

Well then I would get onto the inter web and google, type in best ISO for 60D in video mode.. and see what comes up.. there must be alot of info about the camera out there.. but its a stills camera primarily.. not really a video camera.. so pixel skipping etc in video "mode" would also be a consideration I guess..

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