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View Full Version : Whats ISO for on the GH1?



Drcoffee
05-29-2009, 07:43 AM
Sorry for being basic, but I'm a bit confused about a few things. I'm coming from a video background, where I think cameras basically have just one ISO:

Does changing the ISO, in the GH1 work like a gain + or - setting?

Is ISO the same as ASA?

Would you want to work at the lowest ISO possible for reduced grain/noise?

Cheers
Jon

Ooze3d
05-29-2009, 04:37 PM
It's basically like a gain control, yes. It controls the sensor sensitivity to light and it's similar to analog ASA. A standard sensor has native and artificial ISO levels. The native levels can actually gather more real light, the artificial ones work basically taking the highest native level and boosting the light by software.

The other question is a bit tricky:

If you were shooting raw you would simply want to keep ISO at a standard level, normally below 1600 or 3200 (most cameras have higher ISO levels, but they're not native, I don't know what's the highest native level for the GH1) because you can always change that in post with no visual difference from doing it in camera. You'd have to be careful because extremely low ISO levels can loose info too (say ISO 50)

When you're not shooting raw, which is the case with the GH1, it's up to you. If you need your shot to look ok in very low light situations it's better to use a high ISO even if it's higher than 3200 because it will probably look much better than setting a lower ISO and trying to boost light in post (since you don't have a raw file in post). As I said before, a lower level will give you less noise, but can also lead to less info.

John Caballero
05-29-2009, 05:39 PM
Check this video out. It shows the GH1 menus. ISO on video mode goes only to 1600. Which for a video camera is very good.

http://vimeo.com/groups/gh1/videos/4904780 (http://vimeo.com/groups/gh1/videos/4904780)

It used to be called ASA last century! It became ISO.

anthonybsd
05-29-2009, 07:12 PM
It used to be called ASA last century! It became ISO.
Hah! I grew up in Eastern Europe - there was never no bloody ASA on my films. Or rather as with most of the other Soviet stuff they came up with their own "superior to capitalist" standard for rating which was something between ASA and DIN called "GOST". It was a lot of fun when first Kodak Golds and AGFAs with ISOs appeared on the scene - I imagine quite a few people overxposed the hell out of them.
Looked like this:
http://bosonogoe.ru/uploads/images/b/e/1/b/1/d46b1790c0.jpg

John Caballero
05-29-2009, 07:23 PM
LOL! Such a simple life. No ASA to worry about. Yeah, last century was a different world....

joesant
08-04-2010, 10:44 AM
This is the way I understand this regarding the canon 7D,
Digital cameras have what's called NATIVE ISO which I believe is how the sensors are calibrated to capture light. On the canon 7d the Native ISO's are 160, 320, 640, 1280 anything outside of those ISO settings are using inferior software to increase and decrease the light sensitivity of the sensor which can add noise or grain to your image, so an ISO 200 may not be as clean as ISO 160 or 320 the native ISO of the canon 7D. So if I am correct with this does anyone know what the Native ISO for the Panasonic GH1 is for sure? it seems like people are basing this on the 7D not the GH1.

joesant
08-04-2010, 10:54 AM
ISO is International Standards Organization and ASA is American Standard Association, they are interchangeable and originally referring to FILM sensitivity standards so all ASA or ISO 100 film will react to light the same and cameras and light meters can use those standards to help you calibrate exposure. Digital cameras don't use film so the sensors have to have multiple ISO settings and I believe they are made with Native ISO starting at a base (ISO 160 for the 7D) and doubled from there 160, 320, 640 etc.

Razz16mm
08-04-2010, 12:10 PM
There is one optimum ISO setting for any digital camera. That is the setting that produces maximum dynamic range with correct exposure.

fraustosound
08-04-2010, 01:06 PM
I come from video world and I'm pretty new to using still cameras. Video cameras have one "native" gain setting where no gain is added. Any camera that uses a sensor to generate pictures would be the same. Any setting that adds gain will add noise but it may not be noticeable if you don't boost it too much.

At work we use HDX-900's and they have a 0db, 6db and 12db boost.

Personally I think it's time to abandon the ISO nomenclature and switch to db since our cameras don't use film.

Svart
08-04-2010, 01:41 PM
heh. I come from a photography background and think it should stay ISO!

:)

thisisapocalypse
08-04-2010, 01:45 PM
heh. I come from a photography background and think it should stay ISO!

:)

+1 ISO makes sense to me :)

Razz16mm
08-04-2010, 02:32 PM
Gain doesn't make much sense photographically. It tells you nothing about the light sensitivity of the camera in any case. ISO is a standard that ties your camera, whether film or digital, to absolute light values, so you know how to expose and light for it.

Even with video cameras, I have always used charts and a waveform monitor plus field testing under various conditions to establish a practical range of ISO speeds for my cameras, with and without gain applied, with and without ND or CC filters, and for tungsten vs daylight. Then I can manually expose video just as I would any other photographic medium.
It takes a little more effort but the end result is worth it if you really care about your image quality. With manual exposure you can get a much more refined degree of creative control over your available sensitivity and dynamic range. If you are after "cinematic" quality images this is one of the important skill sets that separates a cinematographer from a videographer.

doccutter
08-04-2010, 04:04 PM
OK, while it's true that folks used to working in film are accustomed to ISO ratings, and yes, I've calibrated many a video camera using a waveform monitor, light meter and grey cards to get the ISO of the camera, the truth is that there is one ISO setting that will perform better than any other setting of the camera, this is the native ISO. Any setting above or below is essentially gaining up or down artificially. I think the OP (any myself included) would love to know what the actual native ISO of the GH1 is. This is vital for squeezing the best possible performance out of the camera. I'm not sure why DSLR's have pretended that "choosing" an ISO is more meaningful than gaining up or down, for me, I'm fine with the camera having an ISO setting, just tell me what the native ISO is!

MR Fanny
08-04-2010, 07:36 PM
yes ISO is supposed to replicate the sensitivity of film in which cameras used to use and everyone/photographers are accustomed to. it is a stills camera first and foremost after all =) I'm happy with ISO.

now lets see what they use in the new AG-AF 100 if they use iso or gain as it is a video camera and not a stills camera.

Homunculus
08-04-2010, 08:07 PM
doccutter and others: to my knowledge i have read in other threads that the gh1 has native ISO's that double I just can't remember hwat they are. they are either 100, 200, 400 etc doubling upwards or something like 320 640 etc. hopefully someone that knows will chime in.
Also in another thread someone kept saying that forum member Kholi uses 320 ISO as standard in all shoots including outdoors which leads me to believe that he may know something we don't in regards to that, that maybe 320 is the native ISO of gh1. I'm just curious why 100 wouldn't be the native. why would you have a LOWER ISo than the native? If native is let's say 320, why would there be a 100 included.

doccutter
08-04-2010, 08:37 PM
Homunculus,

You often have 'negative' gain on video cameras as well, like -3 db. The reason ostensibly is that it's like a one-stop ND, you can use a larger aperture if you need to. On the other hand, I'm often wondering if using one of these negative gain settings is actually the native ISO, and for marketing reasons, they have the 0db gain setting as a norm, but it actually includes gain as well. Technically, gain is gain, so if 0 is the baseline, then gaining down 3 db should increase noise just like +3 does. So again, if we set the GH1 ISO too low, then we will also get noise. The problem with this "multiples" idea is that the difference between 100 and 200 ISO is a full stop, there's no way that gain isn't involved, and as we know Gain == Noise. That's why it's so important to figure out the real ISO of the sensor...

Homunculus
08-04-2010, 08:58 PM
doccutter: thanks for response. however for me at that low level noise seems negligible anyway so i wouldn't really care less about the negligible difference of noise between 100-200 or so ISO, what I care more about is someone mentioning that using the native ISO would perhaps give a higher dynamic range to the camera than artificial ISO's, now THAT'S an improvement worth writing home about and that's the main reason I'm very interested in hearing what the native ISo possibly could be as we could use all the latitude we can get on these DSLR's...

fraustosound
08-04-2010, 09:19 PM
Even with video cameras, I have always used charts and a waveform monitor plus field testing under various conditions to establish a practical range of ISO speeds for my cameras, with and without gain applied, with and without ND or CC filters, and for tungsten vs daylight. Then I can manually expose video just as I would any other photographic medium.
It takes a little more effort but the end result is worth it if you really care about your image quality. With manual exposure you can get a much more refined degree of creative control over your available sensitivity and dynamic range. If you are after "cinematic" quality images this is one of the important skill sets that separates a cinematographer from a videographer.

You are getting into semantics. As a broadcast engineer, I have set up and shaded many a video camera, from older analog and digital SD cameras to modern HD broadcast cameras. Like you I use chip charts, WFM monitors and vectorscopes but I have yet to work with a broadcast level camera that has any form of ISO adjustment. I suppose you can find a way to convert luma voltage readings on a WFM to an ISO rating but that seems pointless from an engineering standpoint. If anything I'd call it signal-to-noise ratio before I call it ISO.

Anyway, I still would like to see proof of which ISO setting on the GH1 and GF1 is 0db gain.

Pietro Impagliazzo
08-04-2010, 09:20 PM
I come from video world and I'm pretty new to using still cameras. Video cameras have one "native" gain setting where no gain is added. Any camera that uses a sensor to generate pictures would be the same. Any setting that adds gain will add noise but it may not be noticeable if you don't boost it too much.

At work we use HDX-900's and they have a 0db, 6db and 12db boost.

Personally I think it's time to abandon the ISO nomenclature and switch to db since our cameras don't use film.

No Frausto, it's the other way around.

+6dBs over what? What is 0db? What the manufacturer determined, but you don't know what is it.

ISO is a standard! ISO100 is ISO100 in whatever system you use.

Homunculus
08-04-2010, 09:37 PM
No Frausto, it's the other way around.

+6dBs over what? What is 0db? What the manufacturer determined, but you don't know what is it.

ISO is a standard! ISO100 is ISO100 in whatever system you use.


are you sure? Many people say that ISO 800 on GH1 is equivalent to ISO 1600 on canon 7d etc. It doesn't seem to be standardized

fraustosound
08-04-2010, 09:46 PM
No Frausto, it's the other way around.

+6dBs over what? What is 0db? What the manufacturer determined, but you don't know what is it.

ISO is a standard! ISO100 is ISO100 in whatever system you use.

When it comes to sensor output, 0db means there is no gain reduction or boost. ISO is a film sensitivity term and has nothing to do with ccd or cmos sensor output voltage.

Chris Light
08-05-2010, 01:27 AM
Anyway, I still would like to see proof of which ISO setting on the GH1 and GF1 is 0db gain.
all the talk of "sweet spot" it too relative...i too would like to know this.

Razz16mm
08-06-2010, 10:12 AM
You are getting into semantics. As a broadcast engineer, I have set up and shaded many a video camera, from older analog and digital SD cameras to modern HD broadcast cameras. Like you I use chip charts, WFM monitors and vectorscopes but I have yet to work with a broadcast level camera that has any form of ISO adjustment. I suppose you can find a way to convert luma voltage readings on a WFM to an ISO rating but that seems pointless from an engineering standpoint. If anything I'd call it signal-to-noise ratio before I call it ISO.

Anyway, I still would like to see proof of which ISO setting on the GH1 and GF1 is 0db gain.

ISO is an illumination reference point. Native ISO is the setting for a digital sensor that produces equal DR above and below 18% gray at the camera's nominal 0 gain setting. Exposing at a different ISO for the same gain setting will trade off shadow noise for highlight protection, or highlight burnout for cleaner shadow detail. Increasing gain above the minimum setting may reset the 18% gray ISO reference point, but it also usually reduces available dynamic range. Noise is amplified and highlights clip sooner. 6dB gain is equal to a one stop shift or doubling of ISO speed. But depending on conditions one may get a better image with no gain.
Rather than specifying an ISO rating, video camera makers specify sensitivity as an f-stop rating at a particular illumination reference, usually 2000 lux or about 200fc. Matching this specification setting on a chip chart will result in 18% gray falling at 50-55IRE on a waveform monitor. One can enter these values into a programmable light meter and get an ISO reference point, but that likely will not be ideal many conditions.
If you are a gaffer prelighting a set, gain tells you nothing about the required light levels or contrast ratios one must provide to establish the look and dynamic range of the recorded scene. Light meters use ISO reference and EV scales.
Gain provides no guidance for adusting ND filters, iris, or shutter speed to achieve a particular look for a scene, shallow DOF for example if one is shooting outdoors on a bright day. If you know your camera's ISO sweet spot, this is much easier to plan, and you can precisely determine your exposure trade offs for the desired result.
It is much more than semantics, it is about knowing your photographic instrument, whether film or digital, to a degree that gives one more precise creative control, especially under conditions where you are shooting without studio control room instrumentation and monitoring conditions. One cannot practically judge exposure in the field with a viewfinder or LCD to a very fine degree, and this is especially true of low end cameras. In camera meters and zebras are pretty crude too. Forget auto iris if you want anything approaching a film like look. The only practical way to get a consistent predictable film like look is with fully manual exposure techniques and intimate knowledge of the characteristics of your camera.

doccutter
08-06-2010, 10:29 AM
I would agree with all that you mention here, but I'd really still just love to know the native ISO of the GH1. Regardless of if we are approaching from a video engineering background or a film background, we still need to know the native ISO of the camera, so we can squeeze the best performance out of it.

Razz16mm
08-06-2010, 10:42 AM
I would agree with all that you mention here, but I'd really still just love to know the native ISO of the GH1. Regardless of if we are approaching from a video engineering background or a film background, we still need to know the native ISO of the camera, so we can squeeze the best performance out of it.

Agreed. Wish I could help more with that question.

fraustosound
08-06-2010, 02:02 PM
I cannot disagree with anything you said Razz, good info all around.

As a video engineer I mostly adjust the camera to suit the lighting whereas you adjust the lighting to suit the camera. Different approaches with the same goal in mind.

Razz16mm
08-06-2010, 02:09 PM
I cannot disagree with anything you said Razz, good info all around.

As a video engineer I mostly adjust the camera to suit the lighting whereas you adjust the lighting to suit the camera. Different approaches with the same goal in mind.

Thanks, actually a bit of both, camera and lighting. The key is to know what the light is doing by using a good incident and/or spot meter, then to take best advantage of it with exposure.
I will post a couple of still frames and exposure info from my old GL2 to illustrate how well shooting video like film can work.

fraustosound
08-06-2010, 02:22 PM
The key is to know what the light is doing by using a good incident and/or spot meter, then to take best advantage of it with exposure.


I'm usually not allowed near any lights, hehe. If it were not for my WFM and vectorscope I would have no idea what's going on. :huh: