100 ASA or 400 ASA in sunny days - video?

[Gary Huff]

Originally Posted by Adriano Moroni

I made many clicps with 200 ISO and 400 ISO. 200 ISO clips are very better.

All things being equal, you should not be able to see any difference whatsoever, save for some less dynamic range.

[Adriano Moroni]

Friends, I've done a lot of tests, shooting in many ways and I've just come home to evaluate them with a good big monitor. Here are my mental results. Maybe they will be wrong but I say this: I haven't used any filter and the best results in absolute I had them in manual choosing 100 ASA and an aperture between f5.6 and f11 (f11 is the maximum limit to get good images). In my opinion is better open more the diaphragm maybe speeding the shutter (1/320) that close the diaphragm (f16) with a slower shutter speed maybe at 1/100. I've been in the countryside, the day was good with sun and clouds. I filmed landscapes in 4K with lots of green and yellow ripe wheat. What surprised me was the fact that with F5.6, 1/100, with 100 ASA I needed an ND filter. But can it be? It seems a bit 'strange because I was not at the beach and the day was not very sunny.
I will go to Africa but I always brought the videocamera with me. The GH5 is a completely new thing that makes me anxious. We hope well. I don't go to visit the african cities, they don't interest me. I'm interested in people.
A consideration I have to do: in this forum I learned a lot, especially the fact of trying on the field the advice all you have given me.

PS:
1) Could someone suggest a good variable ND filter?
2) If someone use a GH5 with lens hood, can you tell me if it is hard to turn the filter? I'm worried the lens hood could bother a lot because I have to make fast shooting.
Thanks

[Cliff Totten]

Not sure if you are up on the latest, but the term ASA is not really used any more. It was replaced by "ISO". Even still, the more accurate term for image sensors would be "gain" as that is actually what is really being applied to the signal off the sensor.

Sensors only have ONE "sensitivity" to light. That sensitivty is adjusted to "0db" by the manufacturer. You can then apply your own user adjustable gain after that.

"Dual gain" cameras simply re-map the same pixel well output to a higher "0db" brightness rating. It's just different "pre-gain" at the collection level. It doesn't change what the sensor actually "saw" in any way whatsoever. A 50% full pixel well will always be 50% full no matter how high you gain up your camera. 100 ISO, 800ISO, 1 million ISO....and your pixel well is still exposed to only 50% full.

"ISO" is not even "exposure" at all in the image sensor world. Only shutter speed and iris affect the image sensors true exposure. Unlike film, ISO/gain has no affect on a sensors exposure in any way at all.

Just thought I would throw this out there as its common to talk about ISO and treat sensors as though they are like film...but nothing could be further from the truth.

[Noa Put]

I don't think this is the answer Adriano was waiting for, even if it was very informative for those who are into these kind of technicalities.

Adriano; when you shoot outside with a low shutterspeed like 1/100 you often will need to apply a nd filter to keep your f-stop at 5.6, even without direct sunlight the incoming light on a cloudy day can be bright enough that you need to apply a extra ND in such a case.

When you use a lenshood you will not be able to turn your variable nd filter anymore without seeing your hand reaching for the filter. You need to leave the lenshood off if you plan on turning the ring while you are recording.

I have used some variable nd filters in the past and found that the cheaper filters gave colorshifts, the expensive ones didn't, I think you can compare this with cheap vs expensive lenses, the more expensive the lenses remain sharper across the frame when wide open, they show less chromatic abberation etc, same for filters you put in front of your lens, it's best not to put some cheap filter in front of a expensive lens.

[Adriano Moroni]

Cliff, thanks for your availabity. I always used videocameras and it is new to me to use camera to make videos. Afrer reading your interesting writings a concept isn't clear to me and I'd like to understand better. I give you an example. If my GH5 has 400 native ISO, if I will use 100 ISO in a very sunny days, what will it happen? The image that I will get will be a little degraded?

[Adriano Moroni]

Originally Posted by Noa Put

I have used some variable nd filters in the past and found that the cheaper filters gave colorshifts, the expensive ones didn't, I think you can compare this with cheap vs expensive lenses, the more expensive the lenses remain sharper across the frame when wide open, they show less chromatic abberation etc, same for filters you put in front of your lens, it's best not to put some cheap filter in front of a expensive lens.

Noa, after many tests in these days I understood that every filter degrades the image quality even if it is expensive. I verify it with a large and good monitor. I tried it many times with a fixed ND Hoya filter. It isn't variable and I think a fixed filter is better than the variable one. I can't think to put a filter so often. brrrrr

[Cliff Totten]

Originally Posted by Adriano Moroni

Cliff, thanks for your availabity. I always used videocameras and it is new to me to use camera to make videos. Afrer reading your interesting writings a concept isn't clear to me and I'd like to understand better. I give you an example. If my GH5 has 400 native ISO, if I will use 100 ISO in a very sunny days, what will it happen? The image that I will get will be a little degraded?

Your question is excellent. And because it is, its not easy to answer....

All camera companies have to read their image sensor and collect a raw linear output. This raw data has no real gain inside of it. But then they need to amplify it and apply some type of gamma respose to it and assemble that into an actual "image". They try to find the nominal "pre-amp" that gives that sensor the best signal to noise ratio.....after they are done with pre-amp settingd, they then call this "0db". You and I then take it from there and we add all the gain we want above 0db.

This "0db" will then be tested in a lab and they try to match up what the estimated ISO would equal to with light meters.

However,...this is not etched in stone. If that company "changes" the pre-amp values on the sensor readout and apply a "different" gamma curve...they now have a NEW "0db" brightness. They have to test this new "0db" and match it up with new ISO lab readings.

On your GH5....just for a minute, forget "ISO" and only watch gain settings. You always want "0db" no matter what gamma you are using. VLog, CineD or Natural can all give different minimum ISO values but you can always use "0db" as your reference. While at 0db, that is the NOMINAL gain amount....for THAT actual gamma curve you are using.

Remember....0db is a SET gain amount that was determined by the camera engineers with their "PRE-Amp" gain that you dont have access to. They could make "0db" equal 100ISO...or 800ISO. They could make 0db equal 25,000ISO. (Would look horrible but they could do it)

Panasonic chose to make "0db" equal arround 400ISO for VLog-L because they needed that much pre-amp to get the most out of that sensor...and make the best "0db" that they could. (The end result was about 400 ISO after they tested it)

Gamma curves with less dynamic range require less pre-amp and their "0db" will equal a different ISO light meter reading. But again,..."0db" should always be the best signal to noise ratio and highest dynamic range for THAT particular gamma curve you are using.

This is why ISO confuses so many people today. I tell people that ISO has nothing to do with actual image sensor exposure and that raw files dont even have any camera ISO in them, only ISO metadata and many people cant understand it. It blows their mind.

I hope is explained this in an easy to understand way!

[Noa Put]

400 iso on the gh5 should give you the cleanest image with the most dynamic range but I doubt if you are able to see a difference from a normal viewing distance to a screen if you shoot at a lower iso.

[Cliff Totten]

Adriano, what gamma curve are you using? This determines its "native ISO".

[Adriano Moroni]

Originally Posted by Cliff Totten

Adriano, what gamma curve are you using? This determines its "native ISO".

As I don't want to modify every clip in post, I'm using "Standard" option. I don't know if I'm doind the right thing.

[Cliff Totten]

Gamma type is your choice. There is no right or wrong. If color grading is not your thing than standard or natural is fine. Im only saying your cleanest image will be 0db on every gamma setting and adding any more gain wont give you any more dynamic range anyway. Standard gammas dont use the entire sensor dynamic range. It already throws away allot so you dont get anything more by adding any more gain.....you just get more noise for nothing in return.

[Adriano Moroni]

Suggest me please. For me it is the first time I will take a 4K documentary in Africa wirh a camera. I always used videocameras. Would you shot 25p or 50p? Now I don't have free time to study v-log, etc. etc. I have to settle for what my GH5 offers me. Which style would you choose instead of "Standard"? How would you set the GH5 please?
Thanks

[Cliff Totten]

First thing...take your camera to your back yard or local park and do test shots! Get to know your camera ASAP.

I cannot tell you 25 or 50p. Nobody can, this is completely your preference.

Im in the US and if I didnt know my GH5 or what VLog was, I would shoot 4k in 29.97p in natural gamma. I dont like 24p that much and I hate 60p. 30p is the perfect middle ground for me and using 30psf (progressive segmented frame) this will give a progressive look over traditional 60i monitors or even 60i broadcast.

Anyway.....shoot right now and test the different profiles and figure out what "you" like.

What is your delivery goal? Are you editing this? Are you delivering it to somebody else? If so, get THEM to tell you what they require.

You need an end goal. Once you know it, you can shoot acordingly.

[Adriano Moroni]

Cliff, I did a lot of tests and for that reason I asked if you had a GH5 how you would set it. Sure I will do my choise but I'd like to know another thought. I have Pal system, do you think me too I could shot 30p? Or is it better 25p for me? If I have to be sincere I like more 25p than 50p. I see a better image quality but I shoot indigenous people they sometimes walk and then run, I need often to walk with fast step behind them with the camera in hand. I'm afraid 25p could create some problems, maybe 50p is better for me.

I don't have to deliver my documentaries. They are for me only. I only do video projections and I like to get a good quality of image. I always make editing of my videos with Edius 9.

[Ron Evans]

25P or 30P will give you problems if you walk fast or run with it in your hand. As you know I am not a fan of slow frame rates preferring the smooth motion. You have to decide yourself, nobody can do that for you only offer their opinion. My opinion, shoot UHD50P, shutter 1/50 ( so you get the motion blur of 25P ) make sure the lens image stabilizer is on so that you have both lens and IBIS active all the time. Before you go shoot some Cine-D or Like 709 and see how they work for your editing. You will have to learn how to set iris, gain and ND as you want. It will not be as easy as your AX100 with auto ND etc