Crop Factor Comparison Shooting 4K DCI: P6K Pro vs P4K

Hi guys, I’m trying to compare crop factor on the Pocket 4K vs Pocket 6k Pro, WHEN SHOOTING 4K DCI ON BOTH.

Please let me know if this is correct:
Pocket 4K is 1.88 crop.
Pocket 6K Pro is 1.67 crop.
Pocket 4K w/ Metabones .71 Speed-booster is (1.88 x 0.71)= 1.33 crop.

So when I compare the 1.33 crop of P4K speed boosted, vs the 1.67 crop of 6k Pro, it’s a difference of 0.34. Is that correct?

If so, how does that 0.34 crop difference look in the real world? Is it pretty negligible?

Real test in a real world

https://www.macchiavello.com/wp/it/il-v ... -del-crop/

Italian but I think the pictures are universal.
No speedbooster only same lens on different camera, and you can download original dng/braw if someone not believe.

Some picture are very near in small room, to break the old mith that crop cause problems on small place. More near to subject you are, less angle you earn, more space you have more ability to move you far from subject.


Inviato dal mio iPhone utilizzando Tapatalk

Am not sure OP's numbers are entirely accurate, but measuring against FF is pointless anyway.

Using the horizontal size of the sensors, a 4K with a .71 speedbooster is, by my count, in a 1.16 ratio with P6K Pro. So a 20mm on the 4k+.71SB will require a 17mm on the 6K at the same distance from the subject for the same field of view (and slightly different depth of field, if no compensating adjustment of the iris is made). Or a 50mm on the 4K is a 43mm on the 6K. And on and on....

It's not a huge difference and why worry anyway? Use either camera to achieve the FOV you're seeking, and no need to do the math.

Am not sure OP's numbers are entirely accurate, but measuring against FF is pointless anyway.

Using the horizontal size of the sensors, a 4K with a .71 speedbooster is, by my count, in a 1.16 ratio with P6K Pro. So a 20mm on the 4k+.71SB will require a 17mm on the 6K at the same distance from the subject for the same field of view (and slightly different depth of field, if no compensating adjustment of the iris is made). Or a 50mm on the 4K is a 43mm on the 6K. And on and on....

It's not a huge difference and why worry anyway? Use either camera to achieve the FOV you're seeking, and no need to do the math.

Thanks John. The reason I ask is because I’m considering upgrading from the Pocket 4K to the 6K Pro, however the larger file sizes of the 6k Pro (when shooting at 6k) are scaring me off a bit. So I thought if I shoot at 4K dci on the 6k pro would it be roughly the same crop as shooting 4K dci on the Pocket 4K?

I like the upgrades of the 6k Pro (internal nds, Sony npf batteries & grip, tilting screen etc) and I like that I can keep a minimal setup without too much rigging. Also some have said the dynamic range is improved as well as noise and low light. But I don’t want to end up with a garage full of hard drives haha!

What are your thoughts, do you think it’s worth the upgrade? Also is it a good idea to shoot at 4K dci on the 6k pro to save some storage space?

This cannot be correct. 6k pro at 4k dci has already more crop than the 4k. So the 4k with speed booster has much wider field of view.

Alas, in haste I misread his original question. Shooting windowed 4K on the 6K of course has a different answer.

The equivalent of windowed 4K DCI on the 6K would be a horizontal of about 15mm versus the equivalent of 26mm on the 4K+.71 speedboost. So in that case, the ratio is 1.74. A 20mm on the 4K+SB would require an 11mm on the 6K windowed at 4K. That's quite a large difference.

If the math is correct.....

As for shooting windowed on the 6K, that's usually less than ideal--noise, artifacts. But you'd have to try.

Real test in a real world

https://www.macchiavello.com/wp/it/il-v ... -del-crop/

Italian but I think the pictures are universal.
No speedbooster only same lens on different camera, and you can download original dng/braw if someone not believe.

Carlo - here's the translation of your blog text (if you don't mind):

The real problem with Crop

It lies in people's heads...

As they say, a picture is worth a thousand words, and a thousand calculations, I thought direct reference images would be the best answer.

The images below are a comparison of the framing of two pocket4k and pocket6k so the 4/3 sensor of the pocket4k (not micro 4/3 as you often read, because that is the mount) versus the Super35 sensor of the pocket6k.

By placing the tripod 10 feet from the window of the photographs these images show that the crop difference is not extreme, not a real problem as so many go about proving with so many absurd calculations.

As can be seen in these comparison shots with different fixed focal lengths 24-28-35-50 in an interior is not so dramatic.

Also since there are so many fixations in tight places (and 10 feet is not a lot) I thought it would be useful to create a simple pattern between the two cameras so you can see how the crop system is less important when we are up close, because the difference in angle is less than being farther away from the subject, but if you are farther away, you can move to compensate for the framing, so it is a false problem.

I keep a spreadsheet of all the cameras and the crops for the various resolutions. I normalize against a 36mm horizontal but the vertical depends on the resolution selected. Since we are selecting 4K DCI window for both, it’s a straightforward comparison between the two sensors.

The Pocket 4K uses 4.63 micron photosites and the Pocket 6K uses 3.76 micro photosites.

The crop of the Pocket 6K is about 2.338x.
The crop of the Pocket 4K is about 1.898x.
When you apply the Metabones Ultra 0.71x focal reducer, your apparent focal is reduced so that a 50mm lens with the SpeedBooster has an apparent angle of view as a 35.5mm lens. So you could say the sensor dimensions appear to be increased by that multiplier and that your crop factor is reduced by that factor.
Therefore the Pocket 4K with the Ultra SpeedBooster has an apparent crop of about 1.348x, greater than traditional film Super35 at about 1.445x. (36mm / 24.9mm)

Some lenses designed for Canon APS-C (crop 1.6x) will actually cover Academy 35 and traditional Super 35. However many of those will vignette using the SpeedBooster.
Some lenses designed for Super 35 may vignette such as Sigma 18-35mm. Lenses designed for ‘full frame’ 135 film will be fine with any SpeedBooster.

6k reference copia.jpg (850.55 KiB) Viewed 12735 times

Another picture that can help you to choose
here you can find all cropping when you change resolution on pocket 6k, i did some shoot to test exactly what is a crop and avoid math work, but real measurement.

ps yes you have bigger file, but additional resolution allow you to have better NR ratio and shoot higher iso with less noise, i nver did comparison test between same shoot file size, but i'm used to big SSD from production camera and Ursa g1 shooting in cdng, actually with braw all is light

I keep a spreadsheet of all the cameras and the crops for the various resolutions. I normalize against a 36mm horizontal but the vertical depends on the resolution selected. Since we are selecting 4K DCI window for both, it’s a straightforward comparison between the two sensors.

The Pocket 4K uses 4.63 micron photosites and the Pocket 6K uses 3.76 micro photosites.

The crop of the Pocket 6K is about 2.338x.
The crop of the Pocket 4K is about 1.898x.
When you apply the Metabones Ultra 0.71x focal reducer, your apparent focal is reduced so that a 50mm lens with the SpeedBooster has an apparent angle of view as a 35.5mm lens. So you could say the sensor dimensions appear to be increased by that multiplier and that your crop factor is reduced by that factor.
Therefore the Pocket 4K with the Ultra SpeedBooster has an apparent crop of about 1.348x, greater than traditional film Super35 at about 1.445x. (36mm / 24.9mm)

Some lenses designed for Canon APS-C (crop 1.6x) will actually cover Academy 35 and traditional Super 35. However many of those will vignette using the SpeedBooster.
Some lenses designed for Super 35 may vignette such as Sigma 18-35mm. Lenses designed for ‘full frame’ 135 film will be fine with any SpeedBooster.

Thank you Rick! So summing up what you’re saying (if I understand correctly), the comparison would be as follows:
2.338x crop for the Pocket 6k Pro shooting 4K DCI, versus:
1.348x crop for the Pocket 4K w/ Ultra speed booster, also shooting 4K DCI

Please let me know if that’s correct. If so, that’s quite a big difference. Would there be a way to see that difference visually somehow, like in frames? The reason is, I’m trying to decide if I should upgrade to the 6k Pro, but the huge 6k file sizes have me on the fence. I shoot BRAW and nor ProRes. I like all the upgrades of thr 6k Pro, and even the ability to punch in is good, however at the expense of twice the file size, not sure if worth it to add all that extra storage space. I usually shoot BRAW 5:1 4K dci on the P4K and it’s pretty manageable.

So my thought was what if I shoot 4k dci on the 6k pro to save some space. Some have suggested it may not be a great idea to shoot mostly windowed 4K on the 6k pro, but rather that I try 6k at 12:1 and see how it compares to 4K 5:1 BRAW on the P4K, file size wise.

Any advice appreciated!

Just to directly answer the OP’s question since everyone has provided the visual comparison or the math. If you are always shooting 4K DCI, you don’t need anything higher that 4K DCI for any or whatever reason (eg. shooting in 6K and downsampling to 4K DCI), the no, you should not upgrade to the 6K camera (P6K, P6K G2, or P6K Pro). As Rick showed you, the crop will be larger on the 6K Pro when shooting in 4K DCI windowed compared to the P4K full sensor + SB.

You are correct.

There are two separate issues that seem to be of interest:
1) recording file sizes of 6K versus 4K and
2) the crop factor that determines your field of view when you compare a windowed 4K DCI on the BMPCC6K versus 4K DCI on the BMPCC4K with an an Ultra SpeedBooster.

Resolution
There are advantages shooting 6K as have previously been stated so the operator of the BMPCC6K can shoot at a higher resolution when it suits their purpose but there’s nothing wrong with shooting 4K on the BMPCC6K is one chooses to do that. I often shoot 2.6K on the BMPCC4K to deliver downscaled HD video. I shoot 2K on the UM4.6K as well as 4.6K 2.4:1 downscaled in post if it suits my requirements.

Crop
Remember shooting ‘windowed’ means you’re recording a lower resolution with a smaller field of view. You also may have options to shoot ProRes HD but downscale from a higher resolution like UHD in camera so that you save media storage when you need that. So your effective crop is greater when you are windowed, but you can use a larger sensor area if you chose so your crop may be that of the full sensor.

The SpeedBooster has been a popular way to provide twice the light to your photosites and 0.71x the apparent focal length of a lens to give you a wider field of view. As long as your taking lens actually covers a larger image circle it works. Another reason to buy lenses that cover 135 film is the freedom it gives you to use a strong SpeedBooster.

Advantages of the BMPCC4K
The SpeedBooster requires a mFT mount and supports taking lenses with EF and F and PL mounts that have a longer focal flange distance.

Even without the SpeedBooster as you have seen you can possibly economize on recording media. The window and downscaling options are designed well for that windowing or downscaling in camera. Downscaling can improve colour and details whether in camera or in post.

It’s hard for the unaided eye to see the differences in your moving pictures between 4K/UHD and 2.6K when you are delivering HD video. Both will be better than recording in an HD window. Tests charts are interesting to pixel peep, but really judge how real subjects look in motion and shoot accordingly. If you are delivering 4K, the BMPCC6K may be a better choice, but when you deliver 2K/HD as I do, the BMPCC4K is a wonderful camera.

The only downside is that the dynamic range of the BMPCC4K is not quite as good as the BMPCC6K and both cameras have less DR than the URSA Mini 4.6K. You have to be careful and watch your light levels and clipping which is easy to do with release 7.3 or 7.9.

100% well intended: you do not want to shoot windowed.

The various compression formats offer great flexibility. Pick one that fits and do not worry about “quality problems” due to compression. Instead, enjoy the benefits of some over-sampling in your 4K timeline.

Please use the full sensor and be happy forever more.

100% well intended: you do not want to shoot windowed.

The various compression formats offer great flexibility. Pick one that fits and do not worry about “quality problems” due to compression. Instead, enjoy the benefits of some over-sampling in your 4K timeline.

Please use the full sensor and be happy forever more.

+1 to this. Whichever camera you choose to use, record the full sensor.
BRAW Q5 is a very efficient codec. Record to that at full sensor on the 6K and I’d bet you’ll find it to be less data than you expected.

Alternatively, if you insist on getting the P6K, you can shoot in 4K with full sensor or 4K DCI in crop 5.7K with the P6K/G2/Pro using Prores HQ or Prores 422, which also will give you reduce file sizes.

100% well intended: you do not want to shoot windowed.

The various compression formats offer great flexibility. Pick one that fits and do not worry about “quality problems” due to compression. Instead, enjoy the benefits of some over-sampling in your 4K timeline.

Please use the full sensor and be happy forever more.

Thank you for the tip! You have me considering the 6k Pro. Any idea how 6k 12:1 file sizes on the 6k Pro compare to 4K DCI 5:1 file sizes on the Pocket 4K?

You are correct.

There are two separate issues that seem to be of interest:
1) recording file sizes of 6K versus 4K and
2) the crop factor that determines your field of view when you compare a windowed 4K DCI on the BMPCC6K versus 4K DCI on the BMPCC4K with an an Ultra SpeedBooster.

Resolution
There are advantages shooting 6K as have previously been stated so the operator of the BMPCC6K can shoot at a higher resolution when it suits their purpose but there’s nothing wrong with shooting 4K on the BMPCC6K is one chooses to do that. I often shoot 2.6K on the BMPCC4K to deliver downscaled HD video. I shoot 2K on the UM4.6K as well as 4.6K 2.4:1 downscaled in post if it suits my requirements.

Crop
Remember shooting ‘windowed’ means you’re recording a lower resolution with a smaller field of view. You also may have options to shoot ProRes HD but downscale from a higher resolution like UHD in camera so that you save media storage when you need that. So your effective crop is greater when you are windowed, but you can use a larger sensor area if you chose so your crop may be that of the full sensor.

The SpeedBooster has been a popular way to provide twice the light to your photosites and 0.71x the apparent focal length of a lens to give you a wider field of view. As long as your taking lens actually covers a larger image circle it works. Another reason to buy lenses that cover 135 film is the freedom it gives you to use a strong SpeedBooster.

Advantages of the BMPCC4K
The SpeedBooster requires a mFT mount and supports taking lenses with EF and F and PL mounts that have a longer focal flange distance.

Even without the SpeedBooster as you have seen you can possibly economize on recording media. The window and downscaling options are designed well for that windowing or downscaling in camera. Downscaling can improve colour and details whether in camera or in post.

It’s hard for the unaided eye to see the differences in your moving pictures between 4K/UHD and 2.6K when you are delivering HD video. Both will be better than recording in an HD window. Tests charts are interesting to pixel peep, but really judge how real subjects look in motion and shoot accordingly. If you are delivering 4K, the BMPCC6K may be a better choice, but when you deliver 2K/HD as I do, the BMPCC4K is a wonderful camera.

The only downside is that the dynamic range of the BMPCC4K is not quite as good as the BMPCC6K and both cameras have less DR than the URSA Mini 4.6K. You have to be careful and watch your light levels and clipping which is easy to do with release 7.3 or 7.9.

Thank you Rick! By what you’re saying, I think the 6k Pro could be a good thing for me to consider. I could always try shooting at 6k 12:1 codec (full sensor) and see how those file sizes compare to 4K DCI 5:1 file sizes on the Pocket 4K. Something to think about I guess.

I could always try shooting at 6k 12:1 codec (full sensor) and see how those file sizes compare to 4K DCI 5:1 file sizes on the Pocket 4K. Something to think about I guess.

And don’t forget: if you can live with more data during capture and rough-cut (media is pretty cheap?), you can then trim your project—while maintaining braw—to reduce long term storage needs.

Don’t know what lenses you have or want, but I think there will be many good deals on EF-glass when more and more people move to RF in the Canon-world.

Thank you Rick! By what you’re saying, I think the 6k Pro could be a good thing for me to consider. I could always try shooting at 6k 12:1 codec (full sensor) and see how those file sizes compare to 4K DCI 5:1 file sizes on the Pocket 4K. Something to think about I guess.

If you look at the tech specs you'll see that the difference is 1 MB/s ... And downsampled prores to 4K in a decent quality is not less !

Good point, Yannick. In my post I was assuming the the same quality but Johnbarnesthe3rd suggested shooting different quality to match the media consumption. I recommend shooting Q0 or Q1 if one can manage it.

Except for VFX plates and deep depth of field wide shots with no motion (where you might want to use either BRAW 5:1 or perhaps BRAW Q0), BRAW Q5 is the codec option to use. Since the compression is based on detail in the frame, if you are shooting with either a shallow depth or the camera is in motion, there is going to be very little in the frame that needs more detail than Q5 delivers. Even at 6K, a BRAW Q5 file is going to be smaller than 4K ProRes. Unless a client requires ProRes capture, there is zero benefit to that codec over BRAW.

Definitely do your own testing, but if the amount of storage needed is a concern IMHO BRAW Q5 is the BMD camera codec you should be looking at using most of the time.

It really does have to be said: the lower compression ratios are a waste of bandwidth for footage not intended for post-production fx. Viewed normally, you won't be able to see the difference. 99% of the time, the level of detail afforded the lowest compression versus the highest will be beneath conscious perception. And what makes detail at that microscopic level "better"? Better for what?

Q5, as already noted, will serve you well, since it adjusts as needed, there's no waste.

Thank you guys so much! You all having me leaning towards upgrading my Pocket 4K to the 6k Pro. I feel like if I experiment with Q5 it may not be as bad as I think file size-wise. I was hoping to not have to deal with insane file sizes and tons of hard drive space, and judging from your replies I feel a little more at ease.

I like the upgrades on the 6k Pro like the internal nd’s, npf batteries, ability to have a more minimal rig without external monitor, not to mention dynamic range improvements and better with noise and low light, as well as having the extra resolution and being able to punch in if needed. I think it may be a worthwhile upgrade.

Thank you Rick Lang, John Paines, Jamie LeJeune, Yannick Willox, Ellory Yu, AndreeMarkefors, etc.

It really does have to be said: the lower compression ratios are a waste of bandwidth for footage not intended for post-production fx. Viewed normally, you won't be able to see the difference. 99% of the time, the level of detail afforded the lowest compression versus the highest will be beneath conscious perception. And what makes detail at that microscopic level "better"? Better for what?

Q5, as already noted, will serve you well, since it adjusts as needed, there's no waste.

Hey John, in low light, is the noise difference between a Metabones .71 speed boosted P4K and a 6K Pro quite noticeable, or is it comparable?

Hello all.

I've resumed this post to ask a question.

I have a Pocket 4K with Metabones Cine Ultra 0.64x.

I'm confused about REAL crop factor of the camera: Metabones site declares 2.02x, others 1.9, here 1,88.

I'd like to know the exact value for personal valuation.

Thanks,
Lamberto

Attached the Metabones scheme.

Sensor size of the PPC4k is 18.96 x 10 mm
But that is when you choose to film in DCI 4096x2160. When you Film in UHD the sensor gets slightly cropped to 3840x2160 and the used size is 17.8 x 10 mm.

So for 16:9 your crop factor is 2.022 and for DCI 4K it is 1.899

Lamberto, that’s a handy chart you posted from Metabones. Metabones as noted uses crop factors based on the diagonal compared to 135 film. That’s probably the industry standard way to do it. However…

For my purposes, I always think in terms of the horizontal crop since that is usually the most useful standard to me (since I don’t shoot 9:16). Over time I have moved away from a variety of aspect ratios and for years now deliver 2.39:1 aspect ratios to all my clients. I shoot with conventional aspect ratios, and the extra headroom allows me to reframe in post as is my habit.

So the industry standard crop doesn’t mean as much to me as my horizontal dimension, and it’s simpler to compare for both spherical and anamorphic lenses. For anamorphic desqueeze in post, rather than expand the horizontal number of pixels, I always shrink the vertical height by an Edit transform corresponding to the squeeze such as 0.719x for 1.33 anamorphic lenses.

DCI is just a specification on DCP delivery on SMPTE Standards (in short).


DCI can be Full 1.90 : 1 , Flat 1.85: 1 and Scope 2.39: 1


4K DCI (WHAT?)

True, I shouldn’t have referred to vague “conventional” aspect ratios in my previous post. I should have said what I meant by that and specified 16:9 aspect ratio as conventional as that is what most modern televisions and computer monitors support at a minimum. Camera sensors from BMD are often 16:9 or DCI Full eg 4096x2160. The exception was the BMPC4K, 4000x2160. They were really gunning for DCI Flat but I assume the resolution of the sensor had to be a multiple of 8. Therefore a sensor 3996x2160 1.85:1 wasn’t feasible.

Sorry Rick, I was referring to OP's post title.

4k DCI is a setting in the Pocket 4k camera.

Hello!

Thank you guys for the kind responses I was referring at 4K DCI in this pecific camera.

to Robert Niessner : I got it! i did not thought about resolution, i usually shoot in 4K DCI format. so the crop will be circa 1.9

to Rick Lang: Excelent explanation about Metabones. Here was my confusion!
Actually i don't care so much about the crop factor and,like you,i use it in a creative way and delivery way. Sometimes i also use MFT native lenses.
I used once a Sirui anamorphic. Great lens.