May 22, 2023 at 10:05 am #214515
What are your reasons for shooting on the Alexa LF, or Mini LF, instead of a Super 35 Alexa?
I understand that the LF and Mini LF have lower noise compared to a S35 Alexa, but the larger sensor also means less depth of field. Therefore, one has to open the aperture of the lens to compensate. Do these two not cancel each-other out?
I understand that the LF or Mini LF is required when working with companies such as Netflix that require a true 4K sensor.
May 22, 2023 at 7:26 pm #214516Roger DeakinsKeymaster
We used the Alexa LF on ‘1917’ because we liked the shallow depth of field as well as the increased information it gave us in comparison to the standard Alexa. The S35 did not exist at that time and we only had a look at that camera when we were in prep for ‘Empire’.
To compensate depth of field between the LF and the S35 wouldn’t it require closing down the iris rather than opening it up?May 23, 2023 at 5:21 am #214520
On ‘1917’ you used the Arri Signature Primes which open up to a T1.8. Would the depth of field have been significantly different if you shot on a S35 Alexa and Master Primes at a T1.4?
I’m not questioning your choices, I’m just trying to understand the benefits of shooting full frame digital.
I understand the increased information.
When I said S35 Alexa, I was referring to the older Alexas such as the Alexa XT Studio, Mini etc. and not the Alexa 35 which has a new sensor.
You’re right, I meant closing down the iris to compensate for the depth of field between the LF and the S35.May 23, 2023 at 2:55 pm #214521
The change of camera/sensor don’t only affect the depth of field. So it’s not a matter of opening the iris and change focal length.
There is a change of texture and noise between cameras, to me quite pronounced I must say, apart the resolution one. There is also the fact that it’s not the same a 32mm lens than a 40mm lens. Even if they match angle of view between sensors the lens are different and aberrations/characteristics are different. It’s known the wider you go the more work Lens makers need to do to keep perfection on a lens. So a 40mm will, generally, be better corrected than a 32mm. So bigger sensors take advantage of that too.
I’m not advocating for the large sensor at all. I’m just saying there is more to it than depth of field. Actually I prefer the look of s35 or even s16.May 24, 2023 at 1:46 am #214524
What’s considered a wide lens is not the same when compared full frame to S35 sensor, so I’m not sure what you mean by less aberration on wider focal lengths.
Do you have any specific examples where lens design is better on the equivalent full frame lens? For example, does a 18mm Signature Prime have less aberration than a 14mm Master Prime?
Regarding the noise advantage of a full frame sensor: If you have to stop down the iris to compensate for the depth of field, is there still a noise advantage to using the larger sensor?May 24, 2023 at 3:03 pm #214532
I didn’t mention wider lenses have less aberration. It’s the contrary actually.
And this has nothing to do with sensor or film sizes. (Sort of).
It’s quite complex issue and I don’t know much of it, so someone maybe can jump in. The mm of a lens is the actual distance between lens focal point to the sensor right? So the shorter this distance the more complex and big design a lens needs to be related to its sensor/film coverage.
Usually if you take any lens series from any manufacturer out there the telephoto lenses are the higher quality ones (in terms of resolving power, aberrations free, vignetting…). Because it’s easier to create a perfect 85mm than a 27mm. But if all you use/rent are master primes or signature this don’t matter much tbh.
But again. I’m not advocating for perfection or anything. Actually I tend to not use many telephoto lenses myself.
Regarding noise. It depends greatly which cameras are you comparing and what formats, what ISOs are you using. But in general terms to me, bigger sensors have less noise even if you need higher ISOs.May 24, 2023 at 7:43 pm #214533Roger DeakinsKeymaster
The depth of field of a 40mm is the same whatever the size of the sensor. With a standard Alexa you would need to shoot on a 32mm (some say wider) to match the field of view of a 40mm on a Large Format camera. A small adjustment to the iris will not change the ‘feel’ of that lens. The additional latitude and resolution of the LF can be an advantage over the standard Alexa but that would not be my main consideration when choosing one camera over the other. The ‘feel’ of the lens is uppermost in my mind.May 25, 2023 at 12:46 am #214534
Not s35 vs LF but you get the idea on how different formats/sensors and lenses compare.May 28, 2023 at 8:31 am #214543
Not s35 vs LF but you get the idea on how different formats/sensors and lenses compare. https://youtu.be/RwgkXcUX984
The only difference I see is the increased resolution and shallower depth of field on the Alexa 65. They look very similar to me.
I didn’t know the Alexa LF had more latitude. Lower noise, yes, but one needs to stop down to match the depth of field of a S35 camera. Going back to my original question, do these two variables not cancel each-other out?May 28, 2023 at 8:36 am #214544
The depth of field of a 40mm is the same whatever the size of the sensor. With a standard Alexa you would need to shoot on a 32mm (some say wider) to match the field of view of a 40mm on a Large Format camera. A small adjustment to the iris will not change the ‘feel’ of that lens. The additional latitude and resolution of the LF can be an advantage over the standard Alexa but that would not be my main consideration when choosing one camera over the other. The ‘feel’ of the lens is uppermost in my mind.
I understand that part. So you’re saying the Signature Prime lenses have a better “feel” than Master Primes? If so, why wouldn’t you use a 32mm Master Prime wide open on a S35 camera instead of a 40mm Signature Prime on the LF at a T2?
Is it simply down to the resolution advantages of the LF camera?May 28, 2023 at 9:15 am #214545
Mathematically speaking if you want to match LF depth of field to a standard Alexa you need to close down your iris by 1.3. Same multiplier you would use to match lenses and angles of view between sensors.
T4 on Alexa vs T5.6 1/3 on LF.
32mm on Alexa vs 40mm on LF.
I understand your question and yes if you really want a s35 depth of field on a LF you will need more light or sensor gain to reach a deeper Tstop to match that look.
But if you really wanted that you won’t use the LF on first place isn’t? If you want the look of a s35 sensor then use a s35 camera.
Also this is no mathematics so lots of factors come to play apart from numbers. Lensing, as Roger said, being a huge one.
General preference nowadays seem to go to the LF look. And we describe that as images who have less depth of field as no one rents the LF to over illuminate to close the iris more. With the new Alexa35 we will see what happens.
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