Going to run a test on my new FS7 to rate the sensor for various shooting modes. Can't seem to find any definitive source on the middle grey value of r709. I've read a couple posts that mention it's "somewhere between 40-50%" etc. And since it's "based" on an output format it seems to make sense that it would be 50% but I'm not sure if Sony has home-brewed some version of it for they're cameras that may function differently--not to mention that my reasoning may be flawed at multiple points along the line here.. Anyone seen any documentation that gives an answer?
FS7: Sony r709 Middle Grey?
- Thread starter LAshooter
- Start date
cameramanben
Well-known member
Hi LAshooter,
some 18% mid gray values:
Rec709(800%) (the base LUT in CineEI) - 44%
S-Log2 - 32%
S-Log3 - 41%
18% at 50% S-Log3/S-Gamut3.cine MLUT
I've just made up the above MLUT which might be handy. This is maps 18% gray under S-Log3/S-Gamut3.cine to 50% IRE, with high contrast. The reason for this is that zebras don't go down below 50%, and that increasing the contrast makes it much easier to judge exposure on a waveform. It's a calibration LUT and definitely no use for filming! ;-)
With that in mind, set the camera to CineEI mode, S-Log3/S-Gamut3.cine. Zet zebra 1 to 50%, with zebra aperture to 1%. If you haven't noticed it before, zebra aperture is the tolerence around the nominal value. The default is 10%, so zebra value plus or minus 5%. 1% is very narrow ;-) .
Make sure that MLUTs are all turned 'ON' in the 'Video' menu and that the ISO is set to the nominal native - 2000 for the FS7.
Now point at an evenly lit gray card. Dial the aperture until zebras cover a suitable portion of the card or the waveform is a nice reasonably horizontal line at 50%.
You should now have the camera precisely on 'correct' exposure according to your card as reference.
Change your LUT to whatever look / LUT / User 3D LUT you wish, or flip over to custom mode and try out whichever gamma settings you are interested in, and provided you don't change the shutter, you keep the ISO at 2000 - some custom mode gammas will initially change it - and lock off the aperture and lighting you will be able to read off 'ideal' 18% gray levels using a waveform monitor.
If you have a test scene lit to that gray card, you can also get a great idea of how different looks compare at nominal exposure,
Ben
some 18% mid gray values:
Rec709(800%) (the base LUT in CineEI) - 44%
S-Log2 - 32%
S-Log3 - 41%
18% at 50% S-Log3/S-Gamut3.cine MLUT
I've just made up the above MLUT which might be handy. This is maps 18% gray under S-Log3/S-Gamut3.cine to 50% IRE, with high contrast. The reason for this is that zebras don't go down below 50%, and that increasing the contrast makes it much easier to judge exposure on a waveform. It's a calibration LUT and definitely no use for filming! ;-)
With that in mind, set the camera to CineEI mode, S-Log3/S-Gamut3.cine. Zet zebra 1 to 50%, with zebra aperture to 1%. If you haven't noticed it before, zebra aperture is the tolerence around the nominal value. The default is 10%, so zebra value plus or minus 5%. 1% is very narrow ;-) .
Make sure that MLUTs are all turned 'ON' in the 'Video' menu and that the ISO is set to the nominal native - 2000 for the FS7.
Now point at an evenly lit gray card. Dial the aperture until zebras cover a suitable portion of the card or the waveform is a nice reasonably horizontal line at 50%.
You should now have the camera precisely on 'correct' exposure according to your card as reference.
Change your LUT to whatever look / LUT / User 3D LUT you wish, or flip over to custom mode and try out whichever gamma settings you are interested in, and provided you don't change the shutter, you keep the ISO at 2000 - some custom mode gammas will initially change it - and lock off the aperture and lighting you will be able to read off 'ideal' 18% gray levels using a waveform monitor.
If you have a test scene lit to that gray card, you can also get a great idea of how different looks compare at nominal exposure,
Ben
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cameramanben
Well-known member
A couple of other notes:
many people use 90% white reflectance as their datum for filming. If you go through the process I described before, once you have lined up to the gray card, you can swap it for white (or use a grayscale) and then measure off the 'correct' level for 90% white in your chosen look / LUT / gamma.
You could read it off the waveform, but if you want to be really nuts precise, set your chosen look, dial your zebras (with 1% aperture) until they cover the bulk of your 90% white reference and you should have a perfect reference for where 90% reflectance should sit. You can also make a note of the zebra value if you then want to work through calibrating other looks.
For actual shooting, I tend to set my zebra aperture to 3%, so that I see a decent band without it being too distracting.
My other note is that if you use zebras rather than the waveform for judging the initial 18% gray level using the LUT I uploaded, then you can easily judge it without filling the frame, ie your gray could be a small part of a test frame, but the zebras will still zing out where the waveform may be hard to read.
many people use 90% white reflectance as their datum for filming. If you go through the process I described before, once you have lined up to the gray card, you can swap it for white (or use a grayscale) and then measure off the 'correct' level for 90% white in your chosen look / LUT / gamma.
You could read it off the waveform, but if you want to be really nuts precise, set your chosen look, dial your zebras (with 1% aperture) until they cover the bulk of your 90% white reference and you should have a perfect reference for where 90% reflectance should sit. You can also make a note of the zebra value if you then want to work through calibrating other looks.
For actual shooting, I tend to set my zebra aperture to 3%, so that I see a decent band without it being too distracting.
My other note is that if you use zebras rather than the waveform for judging the initial 18% gray level using the LUT I uploaded, then you can easily judge it without filling the frame, ie your gray could be a small part of a test frame, but the zebras will still zing out where the waveform may be hard to read.
Wow Ben thanks for the thorough reply and the remapping Lut I'll definitely put it to good use. Above and beyond my friend 
Had just downloaded your lutcalc and was noodling around with it before I flipped over here to check my post. Bare with me I'm coming from the stills world and still trying to wrap my head around all this new information I've been absorbing. Everything you've said makes perfect sense. But I wonder about STD5 r709 in custom mode. I can foresee some low-DR situations (mostly when I'm in control of the lighting) where using that gamma's smaller range could be beneficial as far as data per-stop. Do you know how middle grey is mapped in that gamma exactly?
I'm very comfortable with a meter so after I rate the sensor I wont be using a grey or white card in the field/on set to draw exposure. Will probably find a few luts i like and then use your lutcalc tool to make exposure compensating versions for monitoring.
Had just downloaded your lutcalc and was noodling around with it before I flipped over here to check my post. Bare with me I'm coming from the stills world and still trying to wrap my head around all this new information I've been absorbing. Everything you've said makes perfect sense. But I wonder about STD5 r709 in custom mode. I can foresee some low-DR situations (mostly when I'm in control of the lighting) where using that gamma's smaller range could be beneficial as far as data per-stop. Do you know how middle grey is mapped in that gamma exactly? I'm very comfortable with a meter so after I rate the sensor I wont be using a grey or white card in the field/on set to draw exposure. Will probably find a few luts i like and then use your lutcalc tool to make exposure compensating versions for monitoring.
cameramanben
Well-known member
Thanks LAshooter and to be really honest I couldn't give a precise answer to STD5, but it's going to be around 42%-44%. If you follow the technique I posted above, you can flip over to custom mode, set STD5 and get a solid answer. Just remember to post your result!
What's handy starting off with a log setting is that they have been precisely, publicly defined and once you have your camera correctly exposed for a log curve, by definition if you keep the same aperture, ISO and shutter you will also be at the nominal value for any other gamma setting.
Base gamma standards such as Rec709 (18% = 43% IRE) or sRGB (18% = 48% IRE) are also well defined, but in actual cameras tend to be loose guidelines once knees, black, contrast tweaks etc come into it, though 18% on a Rec709-based look should generally come up in the low forties if percent IRE.
I'm currently getting close to adding Nikon .NCP output to LUTCalc to make my D800 an easier fit with my Sony, but pinning down decently accurate curves for the differing base styles has been a heck of a lot trickier than any of the S-Logs were!
What's handy starting off with a log setting is that they have been precisely, publicly defined and once you have your camera correctly exposed for a log curve, by definition if you keep the same aperture, ISO and shutter you will also be at the nominal value for any other gamma setting.
Base gamma standards such as Rec709 (18% = 43% IRE) or sRGB (18% = 48% IRE) are also well defined, but in actual cameras tend to be loose guidelines once knees, black, contrast tweaks etc come into it, though 18% on a Rec709-based look should generally come up in the low forties if percent IRE.
I'm currently getting close to adding Nikon .NCP output to LUTCalc to make my D800 an easier fit with my Sony, but pinning down decently accurate curves for the differing base styles has been a heck of a lot trickier than any of the S-Logs were!
starcentral
Veteran
LAShooter, there are a slew of caveats when going through this process so I might suggest you read through this thread. It will definitely give you some insights when it comes to rating a camera and as you will see;
http://community.sony.com/t5/F5-F55/F5-Not-really-2000-ISO/m-p/473816#U473816
http://community.sony.com/t5/F5-F55/F5-Not-really-2000-ISO/m-p/473816#U473816
cameramanben
Well-known member
Dennis,
when you say 'slew of caveats' with 'this process' I feel I have to say that the only caveat in relation to the specific process I described for judging mid gray (and by extension 90% white) should be that you use a card you know to be 18% gray. I'll knock up a version for 12% gray cards which I see mentioned on the first page of that thread. Calibrating lightmeters is a related extension to this, but does not effect the basic assessment of what mid gray should be recorded as.
I'm using the axiomatic level of 18% gray for S-Log3 as defined by Sony in their documentation mapped to 50% for zebras. Once you set the camera's exposure to that it is by definition 'correctly' exposed for an 18% gray card. Fix the ISO, shutter and aperture and the EV does not change regardless of which look, LUT, gamma etc you set.
You can then read off IRE levels in different looks with waveform or zebras as I described with confidence. As I say, I'll knock up a version for 12% cards.
With that datum set, you could if you wish set a meter to the same EV conditions (ISO, shutter and aperture) and compare or calibrate it. How you work your meter is between yourself and maybe the linked thread. To be honest I haven't looked at it in a long time after a couple of voices seemed to send it a bit grumpy which is rather a turnoff for me. Provided you get your meter spitting out a value which tallies with what the waveform / zebras tell you, you are good to go. At risk of lighting the blue touchpaper, the meter's ISO setting may well end up a little different to what the camera suggests it is.
Alternatively kick back, relax and pretend you are Douglas Slocombe who ditched his lightmeter altogether
.
when you say 'slew of caveats' with 'this process' I feel I have to say that the only caveat in relation to the specific process I described for judging mid gray (and by extension 90% white) should be that you use a card you know to be 18% gray. I'll knock up a version for 12% gray cards which I see mentioned on the first page of that thread. Calibrating lightmeters is a related extension to this, but does not effect the basic assessment of what mid gray should be recorded as.
I'm using the axiomatic level of 18% gray for S-Log3 as defined by Sony in their documentation mapped to 50% for zebras. Once you set the camera's exposure to that it is by definition 'correctly' exposed for an 18% gray card. Fix the ISO, shutter and aperture and the EV does not change regardless of which look, LUT, gamma etc you set.
You can then read off IRE levels in different looks with waveform or zebras as I described with confidence. As I say, I'll knock up a version for 12% cards.
With that datum set, you could if you wish set a meter to the same EV conditions (ISO, shutter and aperture) and compare or calibrate it. How you work your meter is between yourself and maybe the linked thread. To be honest I haven't looked at it in a long time after a couple of voices seemed to send it a bit grumpy which is rather a turnoff for me. Provided you get your meter spitting out a value which tallies with what the waveform / zebras tell you, you are good to go. At risk of lighting the blue touchpaper, the meter's ISO setting may well end up a little different to what the camera suggests it is.
Alternatively kick back, relax and pretend you are Douglas Slocombe who ditched his lightmeter altogether
.
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cameramanben
Well-known member
I do really appeciate this point which Dennis makes early in that thread:
starcentral
Veteran
I can elaborate, but it's already been extensively discussed in the thread between several members. Lots of good tips, debates and considerations for the keen reader.
But to elaborate for just a minute, for example the angle of the grey card to the lens axis, the quality of light and it's angle to the grey card, and when taking a meter read whether the lens axis or light axis is used - are all factors which can easily skew results so my caution was just to make folks aware of them.
...and this is aside from what level grey card your using, and what level of grey a given light meter is calibrated to which in practically different from meter to meter. As I discovered recently the actual grey calibration value for a specific light meter can be calculated using the meters "constant" value published in the back of the manufacturers manual combined with the formula I posted in this DVX thread : http://www.dvxuser.com/V6/showthrea...00-ISO&p=1986560854&viewfull=1#post1986560854
Now having said ALL OF THIS not everyone is going to care or want to be so precisely scientific about it so if you've gone through the entire process of rating your camera and unable to match the light meter's ISO to the camera set ISO when f-Stop match between lens iris and light meter f-stop it is not the end of the world. You can just use the "new value" ISO on the meter to know when you've got your grey level, it's the repeatability that matters more.
Cheers all,
But to elaborate for just a minute, for example the angle of the grey card to the lens axis, the quality of light and it's angle to the grey card, and when taking a meter read whether the lens axis or light axis is used - are all factors which can easily skew results so my caution was just to make folks aware of them.
...and this is aside from what level grey card your using, and what level of grey a given light meter is calibrated to which in practically different from meter to meter. As I discovered recently the actual grey calibration value for a specific light meter can be calculated using the meters "constant" value published in the back of the manufacturers manual combined with the formula I posted in this DVX thread : http://www.dvxuser.com/V6/showthrea...00-ISO&p=1986560854&viewfull=1#post1986560854
Now having said ALL OF THIS not everyone is going to care or want to be so precisely scientific about it so if you've gone through the entire process of rating your camera and unable to match the light meter's ISO to the camera set ISO when f-Stop match between lens iris and light meter f-stop it is not the end of the world. You can just use the "new value" ISO on the meter to know when you've got your grey level, it's the repeatability that matters more.
Cheers all,
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cameramanben
Well-known member
Dennis,
you misread me. I said I do really appreciate it. I totally, wholeheartedly and completely agree with the quote from you in the previous post.
Please do have a look at my sentence again; I hate to think that you imagine I wrote something mean-spirited and 180 degrees from what I actually did. I'm very sorry if you read it that way.
Back to the specific and limited area of the gray value assessment process I was posting about, if you calibrate the recording level to a gray card the way I described above, you can then also get values for 18% gray in all other gammas and LUTs. Provided the target is evenly lit (which means a reasonably horizontal line on the waveform) it doesn't actually matter for that specific process if the card is even 18%, as you are only comparing one gamma to another, with the card being exposed as if 18% and the S-Log3 log curve a well defined base.
Calibrating a lightmeter does involve more care, but again, if you know what gray your gray is and the waveform line is horizontal it should be pretty straightforward to set yourself a consistent datum.
Thanks in agreement - really, I promise!,
Ben.
you misread me. I said I do really appreciate it. I totally, wholeheartedly and completely agree with the quote from you in the previous post.
Please do have a look at my sentence again; I hate to think that you imagine I wrote something mean-spirited and 180 degrees from what I actually did. I'm very sorry if you read it that way.
Back to the specific and limited area of the gray value assessment process I was posting about, if you calibrate the recording level to a gray card the way I described above, you can then also get values for 18% gray in all other gammas and LUTs. Provided the target is evenly lit (which means a reasonably horizontal line on the waveform) it doesn't actually matter for that specific process if the card is even 18%, as you are only comparing one gamma to another, with the card being exposed as if 18% and the S-Log3 log curve a well defined base.
Calibrating a lightmeter does involve more care, but again, if you know what gray your gray is and the waveform line is horizontal it should be pretty straightforward to set yourself a consistent datum.
Thanks in agreement - really, I promise!
,Ben.
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cameramanben
Well-known member
Oh heck,
it seems I'm on a roll today! I just got home and tested out that 18at50 LUT I posted. Something is a bit off as a precise internal MLUT so please leave it for now. I'll repost when I've checked things through,
Ben
it seems I'm on a roll today! I just got home and tested out that 18at50 LUT I posted. Something is a bit off as a precise internal MLUT so please leave it for now. I'll repost when I've checked things through,
Ben
All good points guys. There are a significant number of factors involved in getting an accurate reading, here are my two cents on a few of the basic setup-type questions (As much of the technical workings of video is something that still alludes me.) These may be obvious to some people but in the interest of recording some useful basics for future readers I'll put them down here. And I suspect that they are more likely the reasons for differences in the other threads between peoples personal ratings of the FS7 (I recall various numbers from 800-1250) rather than some internal technical difference between individual cameras.
Uniformity of reflectance of the card: Some people suggest tipping the card down a bit. This is a good suggestion most of the time. If you angle the card in any direction away from the general direction of the light source it will have the same effect. The key is that any specular highlights are cast off away from the lens as this can significantly increase exposure. Ideally the source won't come from the general vicinity directly behind the camera unless it's a large soft source or multiple point sources spread evenly around the lens such that the return from the card is even as well (for my part I'll be using two 4bank kinos, one above and one below the lens.)
Meter: Besides your meter being calibrated for 12% or 18% some meters will drift over time. At least in Los Angeles, there are places you can send your meter in to be recalibrated, I'm sure this isn't an option for everyone though. I myself use an old L-508 that I got off ebay about 15 years ago. The meter is probably 25 years old, is battle tested and sees a lot of use. But I've tested it against many other meters, there's very often a difference of about 1/3 stop either way but mines bang on in the middle so I'm confident its accurate.
Angle of reading: The proper angle in this situation is definitely to match the plane of the card with the plane of the meter's photocell under the lumisphere. Lumisphere up, since the photocell recedes with the lumisphere you will get inaccurate readings in this mode unless you meter directly towards the light source (which you don't want to do in this situation. **Unless your light source is directly behind the camera.)
Lens: If you're using still lenses as I'm sure many people are, there can be a significant discrepancy between any two lenses at a given fstop. As much as 2/3 stop is not rare. I would say 1/3 stop deviations between lenses is at least as common as no deviation at all. Zoom lenses will pass light at different efficiencies across zoom range--1/3-1/2 stop difference from the wide end to the long end is not uncommon. etc. etc.
As much as a lot of us desire optimal conditions and unequivocal scientific answers (I'm one of those people most the time too), making a beautiful image is equal parts art and science. Know your equipment, know its capabilities, know its limitations, use your equipment to achieve your vision not to tell you it.
Uniformity of reflectance of the card: Some people suggest tipping the card down a bit. This is a good suggestion most of the time. If you angle the card in any direction away from the general direction of the light source it will have the same effect. The key is that any specular highlights are cast off away from the lens as this can significantly increase exposure. Ideally the source won't come from the general vicinity directly behind the camera unless it's a large soft source or multiple point sources spread evenly around the lens such that the return from the card is even as well (for my part I'll be using two 4bank kinos, one above and one below the lens.)
Meter: Besides your meter being calibrated for 12% or 18% some meters will drift over time. At least in Los Angeles, there are places you can send your meter in to be recalibrated, I'm sure this isn't an option for everyone though. I myself use an old L-508 that I got off ebay about 15 years ago. The meter is probably 25 years old, is battle tested and sees a lot of use. But I've tested it against many other meters, there's very often a difference of about 1/3 stop either way but mines bang on in the middle so I'm confident its accurate.
Angle of reading: The proper angle in this situation is definitely to match the plane of the card with the plane of the meter's photocell under the lumisphere. Lumisphere up, since the photocell recedes with the lumisphere you will get inaccurate readings in this mode unless you meter directly towards the light source (which you don't want to do in this situation. **Unless your light source is directly behind the camera.)
Lens: If you're using still lenses as I'm sure many people are, there can be a significant discrepancy between any two lenses at a given fstop. As much as 2/3 stop is not rare. I would say 1/3 stop deviations between lenses is at least as common as no deviation at all. Zoom lenses will pass light at different efficiencies across zoom range--1/3-1/2 stop difference from the wide end to the long end is not uncommon. etc. etc.
As much as a lot of us desire optimal conditions and unequivocal scientific answers (I'm one of those people most the time too), making a beautiful image is equal parts art and science. Know your equipment, know its capabilities, know its limitations, use your equipment to achieve your vision not to tell you it.
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cameramanben
Well-known member
Totally agree LAshooter, particularly that last sentence, plus of course we have the luxury of far more usable dynamic range than when the likes of Ansel Adams were developing zones or even when video shooters were working with U-Matic, Beta-SP and then Digibeta. I personally think that consistency is the big thing. If I was shooting mostly with 'T' stop cinema lenses I'd probably get my lightmeter out more, but as you mention I'm one of those who spend most of their time with 'f' stop stills lenses. In my case zebras and waveform help avoid issues like the stills lens variation as they come after the light has hit the sensor.
I remember when I was loading that different cameramen would end up with different printer lights - different people, different meters - but would be consistent to themselves. Mind you the only 'f'-stop stills lenses I would regularly come across were PL-converted Canon 300mm f2.8s.
I'm obviously a bit of a nut for the maths behind it all, but to be honest when I'm shooting I'm much more of a hand-wavy-arty-fart. If it looks nice, I'm happy (though a quick flick of the waveform or zebra is a great reassurance)!
Anyway, on my bedevilled LUT I realise I've actually been very silly. When I double checked the LUT I did it with Resolve Live, completely forgetting that the scale on the waveform is 0-1023 data range from the SDI feed. I lined up to the 50% dotted line, which is 10-bit 512 - half way over data range - rather than 502 - which is 50% of legal range (876/2 + 64). If I had just trusted the zebras and the fact that I have done this a number of times before all would have been well, but I managed to completely confuse myself in double checking. D-oh!
I have uploaded another version - which this time I know I'm happy with (although the others should actually work OK after all!). Link here:
18at50 S-Log3/S-Gamut3.cine MLUT
Ben
I remember when I was loading that different cameramen would end up with different printer lights - different people, different meters - but would be consistent to themselves. Mind you the only 'f'-stop stills lenses I would regularly come across were PL-converted Canon 300mm f2.8s.
I'm obviously a bit of a nut for the maths behind it all, but to be honest when I'm shooting I'm much more of a hand-wavy-arty-fart. If it looks nice, I'm happy (though a quick flick of the waveform or zebra is a great reassurance)!
Anyway, on my bedevilled LUT I realise I've actually been very silly. When I double checked the LUT I did it with Resolve Live, completely forgetting that the scale on the waveform is 0-1023 data range from the SDI feed. I lined up to the 50% dotted line, which is 10-bit 512 - half way over data range - rather than 502 - which is 50% of legal range (876/2 + 64). If I had just trusted the zebras and the fact that I have done this a number of times before all would have been well, but I managed to completely confuse myself in double checking. D-oh!
I have uploaded another version - which this time I know I'm happy with (although the others should actually work OK after all!). Link here:
18at50 S-Log3/S-Gamut3.cine MLUT
Ben
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starcentral
Veteran
Ben, I updated my post. Sorry about that I was reading on blackberry whilst up at the cottage so misread :beer:
LAShooter, I'm glad you've gone into more details about just some of the caveats I mentioned. In fact I can alter the waveform monitor reading by over a FULL stop depending on the tilt of the gray card, where the light is placed, and the type of light used.
I'd be curious to hear about what value you come up with when you do your rating exercise. I'm also using the L-508 and if I want it to match my F55 for what I think is the right angle of grey card to get right reflectance for IRE reading I'm about a full stop off. This is using 3 different brand lenses from Zeiss CP.2, Nikon AIS, and Canon PL Cine Zooms. I expect my meter to be about at least 1/2 a stop off because of the calibration to 11.2% instead of the 18% grey value the camera is calibrated to which leaves me with still about a half stop difference.
Based on my setup I would therefore rate the F55 as an 800 ISO camera and if the F5/FS7 is in line with the F55 in terms of factory calibration and I were to repeat my test I'd likely come up with 1600 ISO as its rating.
Cheers,,
LAShooter, I'm glad you've gone into more details about just some of the caveats I mentioned. In fact I can alter the waveform monitor reading by over a FULL stop depending on the tilt of the gray card, where the light is placed, and the type of light used.
I'd be curious to hear about what value you come up with when you do your rating exercise. I'm also using the L-508 and if I want it to match my F55 for what I think is the right angle of grey card to get right reflectance for IRE reading I'm about a full stop off. This is using 3 different brand lenses from Zeiss CP.2, Nikon AIS, and Canon PL Cine Zooms. I expect my meter to be about at least 1/2 a stop off because of the calibration to 11.2% instead of the 18% grey value the camera is calibrated to which leaves me with still about a half stop difference.
Based on my setup I would therefore rate the F55 as an 800 ISO camera and if the F5/FS7 is in line with the F55 in terms of factory calibration and I were to repeat my test I'd likely come up with 1600 ISO as its rating.
Cheers,,
Dennis, I'll post the full results of my test later this week once completed for sure.
I still wonder about the whole 11.2%/12%/16%/18% meter thing though. I have to admit the implications of all the math is beyond me so I certainly don't want to suggest you're wrong, I really have no idea where the truth lies. Just seen this debated for years and am always surprised how little hard data on it is available, statements about it from manufacturers, or people running tests between meters that are supposedly calibrated differently. For instance, my L508 has always been within 1/10 of the sunny 16 rule in direct sunlight every time i test it. If a large portion of the meters out there are a full half off wouldn't you see "why doesn't my meter conform to sunny 16" posts all over the internet?
I work as a camera and lighting tech in the stills industry 5-6 days a week and use my meter and check exposures all day, my eyes can easily detect 1/10 stop exposure shifts in most circumstances. And I know exposure is ultimately subjective but I feel like I would absolutely notice a half stop difference in my meter compared to others. Also, you'd think a company like sekonic, the gold standard of the film and stills industry for decades would calibrate their meters to what's widely considered industry standard 18% grey? I mean I don't really know I could be wrong, I don't know any pros that meter grey cards I only know ones that meter light so maybe sekonic and other manufacturers aren't too concerned--their engineers designed their meters one way decades ago and nobody's really complained or noticed yet so why change something that sells.. Anyways just thinking out loud, would be really interested to see a definitive test on this issue somewhere.
I still wonder about the whole 11.2%/12%/16%/18% meter thing though. I have to admit the implications of all the math is beyond me so I certainly don't want to suggest you're wrong, I really have no idea where the truth lies. Just seen this debated for years and am always surprised how little hard data on it is available, statements about it from manufacturers, or people running tests between meters that are supposedly calibrated differently. For instance, my L508 has always been within 1/10 of the sunny 16 rule in direct sunlight every time i test it. If a large portion of the meters out there are a full half off wouldn't you see "why doesn't my meter conform to sunny 16" posts all over the internet?
I work as a camera and lighting tech in the stills industry 5-6 days a week and use my meter and check exposures all day, my eyes can easily detect 1/10 stop exposure shifts in most circumstances. And I know exposure is ultimately subjective but I feel like I would absolutely notice a half stop difference in my meter compared to others. Also, you'd think a company like sekonic, the gold standard of the film and stills industry for decades would calibrate their meters to what's widely considered industry standard 18% grey? I mean I don't really know I could be wrong, I don't know any pros that meter grey cards I only know ones that meter light so maybe sekonic and other manufacturers aren't too concerned--their engineers designed their meters one way decades ago and nobody's really complained or noticed yet so why change something that sells.. Anyways just thinking out loud, would be really interested to see a definitive test on this issue somewhere.
starcentral
Veteran
I don't know where the truth lies either, and mostly I'm sharing what some others on the internet have indicated about light meters and why many of us are finding our ISO to be off on the Sony F5 & F55 and now FS7 cameras. To me there is some merit in the fact that meters are actually calibrated to different values then 18% grey. Those posts are all over the internet from DSLR forums to some video based forums like DVX and DVInfo. The big problem with DSLR's and photography however is there are at least 5 standards a manufacturer can use when rating ISO on their digital stills camera, so there is an even bigger issue since it allows manufacturers to work apart from each other instead of having one common standard.
But on the internet there are general statements like "Sekonic is actually 14%" etc.. which is way off from the values I calculated using Sekonic's own data in the back of the manual for L-508, and 758. Then there is this article and series of posts following it all of which contradict one another: http://photo.stackexchange.com/ques...and-how-do-i-make-a-18-gray-card-in-photoshop Posts like this are all over the internet offering no real concrete answers, only theories.
As for the sunny 16 rule I haven't tried it myself, generally if I shoot stills on a DSLR I'm using the camera in manual mode and internal meter to judge exposure. But I will give it a shot today with my L-508 and see what it says.
As Fox Mulder would say, the truth is out there Scully.
But on the internet there are general statements like "Sekonic is actually 14%" etc.. which is way off from the values I calculated using Sekonic's own data in the back of the manual for L-508, and 758. Then there is this article and series of posts following it all of which contradict one another: http://photo.stackexchange.com/ques...and-how-do-i-make-a-18-gray-card-in-photoshop Posts like this are all over the internet offering no real concrete answers, only theories.
As for the sunny 16 rule I haven't tried it myself, generally if I shoot stills on a DSLR I'm using the camera in manual mode and internal meter to judge exposure. But I will give it a shot today with my L-508 and see what it says.
As Fox Mulder would say, the truth is out there Scully.
morgan_moore
Major Contributor
Surely the answer is in the question; middle grey is grey in the middle. 50-50-50 where 0-0-0 is black and 100-100-100 is clip
For 709 you are not adding a LUT so what goes in will come out. WFM at 50 in camera should lead to WFM at 50 in post.
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I would expect to hit this value using a grey card or an incident light meter just in front of the subject (being the grey card)
S
For 709 you are not adding a LUT so what goes in will come out. WFM at 50 in camera should lead to WFM at 50 in post.
==
I would expect to hit this value using a grey card or an incident light meter just in front of the subject (being the grey card)
S
starcentral
Veteran
Ok, 4pm EST here in the Toronto area. Not a cloud in the sky. Sekonic L-508 set to 200th shutter speed and 200 ISO. My meter reads 2/10th's short of f16. 1/10th if I wiggle it around like a crazy man, but generally it reads 2/10ths short consistently.
starcentral
Veteran
OK for OCD members:
There is a 1/10th of a stop difference between 24fps at 1/48th shutter and say a meter reading of 1/200th shutter at 200 ISO if looking specifically at the sunny 16 rule. Our friends in PAL land don't have this extra 1/10th stop because at 25fps the shutter is 1/50th which would be a full 3 stops off from 200th at 200 ISO.
Still only fractions I understand, but still.
There is a 1/10th of a stop difference between 24fps at 1/48th shutter and say a meter reading of 1/200th shutter at 200 ISO if looking specifically at the sunny 16 rule. Our friends in PAL land don't have this extra 1/10th stop because at 25fps the shutter is 1/50th which would be a full 3 stops off from 200th at 200 ISO.
Still only fractions I understand, but still.
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