C500: C500 Mark II: Observations from a C200 point of view

[jcs]

Chris and JCS: I think your math on ISO increase is either coming from remembrance of the inverse square principle or from working with "speed booster" adapters where we almost literally squeeze the image circle down and thereby increase its intensity. But that's not what's happening here, we're merely sampling a larger area of the image circle--the ISO doesn't change.

Imagine a hypothetical lens with a 10" large image circle. You put up an 8x10 sensor (of a fixed ISO, let's say) to capture it and you get X for an appropriate exposure. Now tear that sensor in half twice, and it's still the same exposure (X), but you're only sampling 1/4 of the first image. Now tear it to a full-frame size, s-35, and s-16 and you would continually get a smaller and smaller portion of that original angle of view (fewer degrees, rendering the same lens more telephoto) but still the same exposure.

In other words the over-exposed image looks over exposed because it's over-exposed. Crop-factor math only matters with respect to trying to maintain the same DOF in the smaller sensor (on the "wider" lens) by opening to a wider aperture--in which case you would need that much less ISO in order to keep exposure "X" the same. X stays the same

Perhaps you missed this:

If you don't care about matching DOF and FOV, set the C200 to F5.6 in this example (same as the FF set up: focal length and crop factor won't affect exposure. Prove it to yourself with a zoom lens with constant F-stop (ideally T-stop) as well as enabling, disabling the C500's II S35 and S16 crop settings).

I posted equivalence math and examples in the event the OP wanted to match cameras in DOF + FOV + exposure.

This info comes from doing the actual tests and verifying that the math is correct (including ISO):

[Shot with the Sony A7S and Canon lens (no SpeedBooster)]

Shot 1 (FF):

Shot 2 (cropped):

Are these shots nearly identical? From https://brightland.com/w/the-full-frame-look-is-a-myth-heres-how-to-prove-it-for-yourself/

When I first posted these results 5 years ago, many folks didn't want to believe the Full Frame Look was a myth- perhaps that's still the case with the downvote.

An interactive example: https://dofsimulator.net/ (for DOF & FOV)

 

[jcs]

That's a great explanation. For evaluation purposes if trying to match DOF between sensors and analyzing dynamic range, is it better to just leave ISO alone and adjust shutter speed?

This is cool, I haven't learnt anything on dvxuser in a while!

Simplified: focal length & crop factor don't affect exposure. So you can simply match camera settings and see what the sensor is doing; however DOF and FOV won't match between different sensor sizes. If you want to match DOF (and FOV), you'll need to use the equivalence equations by adjusting aperture, focal length, and ISO.

 

[NorBro]

That's a great explanation. For evaluation purposes if trying to match DOF between sensors and analyzing dynamic range, is it better to just leave ISO alone and adjust shutter speed?

I've seen [online] some people do their tests like that and they keep their subjects as still as possible to avoid any motion.

 

[rob norton]

Simplified: focal length & crop factor don't affect exposure. So you can simply match camera settings and see what the sensor is doing; however DOF and FOV won't match between different sensor sizes. If you want to match DOF (and FOV), you'll need to use the equivalence equations by adjusting aperture, focal length, and ISO.

OK but why not adjust shutter speed and keep both cameras at their native ISO? Or should DR be tested separately?

 

[jcs]

OK but why not adjust shutter speed and keep both cameras at their native ISO? Or should DR be tested separately?

You can set up both cameras with exactly the same settings to test the sensor for noise, DR, etc. Just focus both cameras on the target. You can crop the wider angle shot to match the other in post (to make comparisons easier). Even use the same lens- you don't care about the crop/DOF/FOV in this case. When using the same lens (focal length) and all matching settings: if you crop the FF camera in post by 1.5, it should closely match the crop camera in DOF and FOV, since you're doing the same thing the crop camera does in camera, in post (there will be a difference in detail and visible noise, however for a DR & color test, this shouldn't be a major issue).

 

[NorBro]

The same settings for certain cameras will not always provide you accurate results, which is why so much testing is flawed.

 

[Eric Coughlin]

OK but why not adjust shutter speed and keep both cameras at their native ISO? Or should DR be tested separately?

And break the 180 degree shutter guideline? We're not shooting Saving Private Ryan here. Native ISO is a myth; I make little point to shoot at it as I often get better results at other ISOs. Native ISO is often noisier than lower ISOs, and I'd often prefer the increase of dynamic range in the shadows that lower (below 800) ISOs give me. Adjust NDs, aperture, and ISO to get proper exposure, leave shutter to 180 degrees except in rare circumstances where a different shutter look is desired.


Edit: ...Hmm, I guess you were talking for testing purposes of still frames, in which case, ignore the above comment. But it's too late, I already put the enormous effort into typing that so rather than delete this post you can feast your eyes on my work above.

 

[Guest]

Chris and JCS: I think your math on ISO increase is either coming from remembrance of the inverse square principle or from working with "speed booster" adapters where we almost literally squeeze the image circle down and thereby increase its intensity. But that's not what's happening here, we're merely sampling a larger area of the image circle--the ISO doesn't change.

Imagine a hypothetical lens with a 10" large image circle. You put up an 8x10 sensor (of a fixed ISO, let's say) to capture it and you get X for an appropriate exposure. Now tear that sensor in half twice, and it's still the same exposure (X), but you're only sampling 1/4 of the first image. Now tear it to a full-frame size, s-35, and s-16 and you would continually get a smaller and smaller portion of that original angle of view (fewer degrees, rendering the same lens more telephoto) but still the same exposure.

In other words the over-exposed image looks over exposed because it's over-exposed. Crop-factor math only matters with respect to trying to maintain the same DOF in the smaller sensor (on the "wider" lens) by opening to a wider aperture--in which case you would need that much less ISO in order to keep exposure "X" the same. X stays the same

Just as not to confuse anyone, you just reiterated the same things JCS did. So, JCS’s equation and your explanation both overlap. You may have skimmed over his post.

 

[rob norton]

And break the 180 degree shutter guideline? We're not shooting Saving Private Ryan here. Native ISO is a myth; I make little point to shoot at it as I often get better results at other ISOs. Native ISO is often noisier than lower ISOs, and I'd often prefer the increase of dynamic range in the shadows that lower (below 800) ISOs give me. Adjust NDs, aperture, and ISO to get proper exposure, leave shutter to 180 degrees except in rare circumstances where a different shutter look is desired.


Edit: ...Hmm, I guess you were talking for testing purposes of still frames, in which case, ignore the above comment. But it's too late, I already put the enormous effort into typing that so rather than delete this post you can feast your eyes on my work above.

Haha I'll take it. I'll use lower ISOs next time I shoot something.

 

[Barry G]

Haha I'll take it. I'll use lower ISOs next time I shoot something.

On the canon’s.. shooting at 500, 400, even 200 has been a good strategy to avoid noise in the shadows, at the expense of highlight range. I’ve found the c500II to look great at 800, and while there is some noise in the shadows, it’s much nicer noise than the c300ii. I’ve been able to dig into it a little, if necessary, and generally there seems to be an improvement in detail in the lower nether regions.

Btw. Eric is exactly right in his comments about DR and Ff vs S35 - any increased DR is coming in the shadows, not the highlights..given similar sensor specs. Some of the c200/c500 tests I’ve seen, indicate a little better highlight range in the c500, but this wouldn’t be due to sensor size alone.

 

[djangosan]

Just as not to confuse anyone, you just reiterated the same things JCS did. So, JCS’s equation and your explanation both overlap. You may have skimmed over his post.

I did indeed, sorry! I saw this part of his formula "* Multiply the ISO by the crop factor squared" and read that as saying that changing frame size independently affected ISO.

 

[djangosan]

That's a great explanation. For evaluation purposes if trying to match DOF between sensors and analyzing dynamic range, is it better to just leave ISO alone and adjust shutter speed?

This is cool, I haven't learnt anything on dvxuser in a while!

It shouldn't matter, but it wouldn't be a bad idea to help keep everything equivalent. The same sensor will perform differently in the highlights and shadows at 1600 ISO than at 200 ISO, even at the correct exposure for both.

 

[djangosan]

Perhaps you missed this:


I posted equivalence math and examples in the event the OP wanted to match cameras in DOF + FOV + exposure.

I'm sorry JCS. My bad. I didn't understand you were saying it that way. I saw "* Multiply the ISO by the crop factor squared" and thought, "well that's bad info." Now I'm getting that you were just giving the DOF & FOV equivalence calculations.

And of course, you're right. There is no Full frame look, just an equivalent FOV/DOF. (I used to send people to that DOF simulator all the time.)

Thanks for tolerating my misreading and for putting it nicely.

 

[chris f]

This is super helpful, I didn't realize about the multiplying the ISO as well. I was under the impression (ala speedboosters) that full frame meant that more light was being captured by the sensor and would affect exposure as well.

Which if FF is basically just giving you a different field of view (you could always choose a different lens instead to achieve the same thing) and the option to more easily achieve shallower depth of field (something I rarely if ever want) to me the makes me question even further the need to have full frame in a mid range camera. It seems like the only real advantage as far as image quality is concerned is the fact that it also can be shot in 6K which when downsampled to 4K will create a slightly sharper image and smaller noise/grain.

Is this about right?

 

[NorBro]

As far as the "FF look", IMO, it depends on how you're shooting.

What I'm seeing more of is wider lenses being used on FF sensors, and that's a look I'm starting to love (a medium format-like look).

If you're going for that 20mm f/1.4 on a FF sensor, there are practically zero options available to replicate it on a S35 sensor. The Sigma 14mm f/1.8 would be the closest. But once you stop down a lot and add a few mms then it's more doable - and mathematically equal - with other lenses.

 

[markfpv]

This is super helpful, I didn't realize about the multiplying the ISO as well. I was under the impression (ala speedboosters) that full frame meant that more light was being captured by the sensor and would affect exposure as well.

Which if FF is basically just giving you a different field of view (you could always choose a different lens instead to achieve the same thing) and the option to more easily achieve shallower depth of field (something I rarely if ever want) to me the makes me question even further the need to have full frame in a mid range camera. It seems like the only real advantage as far as image quality is concerned is the fact that it also can be shot in 6K which when downsampled to 4K will create a slightly sharper image and smaller noise/grain.

Is this about right?

I'm not sure there's a "right" or "wrong" - when deciding to purchase a full frame camera... but I do agree with your assessments on what the "real advantages" should be.
For my personal taste, shooting s35 with 16mm lens speed boosted to 11mm is just lovely (T3 becoming T2)

 

[NorBro]

Yea, it's worth noting E-mount cameras do have that luxury, but then they may lose some of their AF.

Always a trade-off...

 

[chris f]

As far as the "FF look", IMO, it depends on how you're shooting.

What I'm seeing more of is wider lenses being used on FF sensors, and that's a look I'm starting to love (a medium format-like look).

If you're going for that 20mm f/1.4 on a FF sensor, there are practically zero options available to replicate it on a S35 sensor. The Sigma 14mm f/1.8 would be the closest. But once you stop down a lot and add a few mms then it's more doable - and mathematically equal - with other lenses.

Ok, yes. I agree, if you're wanting the super wide + super shallow look then it's way easier (or depending on the shot, only possible) on a FF camera. This seems to be the strongest (and maybe only) reason to utilize a FF sensor then, correct?


I do love the look from films like Revanant that have that look - getting wider fov and closer to the characters to provide an interesting perspective, but I'm thinking for most of my uses I wouldn't be replicating this look....

 

[NorBro]

That's the only real advantage I would personally say there is.

After seeing what the ARRIs did for more than a decade, everything else is psychological nitpicking.

 

[NorBro]

Maybe the other advantage is a decision-based one.

The desire - justified or not - for FF sensors from certain people/companies could turn into a very real request.

I don't work for anyone like that and never will so it wouldn't matter to me, but it could affect people in the higher end of production who work for big companies, or the 1%.