50D Raw video

[Andy600]

wouldn't a very small focal length lens create a very shallow depth of field?

No, the opposite.

BTW, DOF in crop mode is exactly the same as it would be in non-crop when talking about raw video.

[Monti]

No, the opposite.

BTW, DOF in crop mode is exactly the same as it would be in non-crop when talking about raw video.

yeah well how does that been worked out?

to my understanding
crop mode multiplies the f stop value for depth of field

[1%]

Does the DOF change when you zoom in on a cr2?

[Monti]

Does the DOF change when you zoom in on a cr2?

yeah well let me think about it...

we talking about framing the scene isnt it?

so lets say i shoot a person head

my depth of field is like from his nose to his ear

that is shallow one.

now if we zoom in in cr2 we get what?

head is choped half and we need to reframe it

when we reframe it what happens?

depth of field is not narrow anymore

now my depth of field is whole head and much more

not as shallow as it was when i frame just nose and ear

why is that?

because crop mode means 50 mm becomes 250 mm

now i have to shoot from distance not 4 meters but like 20 meters to get kinda same framing

and 20 meters gives me what? huge fat bulky depth of field that i can even bring a bus into it

p.s. of coz u dont get head shot on 50 mm from 4 meters
but u got the point

[Andy600]

@Monti - It's a tricky concept to get your head around but DOF does not change when you punch between crop and non-crop because there is no optical difference between the two modes other than framing. It is still seeing the same pixels but in normal mode 2/3rds are thrown away through line-skipping with the remaining pixels brought back together. Of course, if you reposition and refocus you will have affected DOF because you moved further away from the subject. At least, that's how I understand things but it fries my brain to think about it.

[Monti]

@Monti - It's a tricky concept to get your head around but DOF does not change when you punch between crop and non-crop because there is no optical difference between the two modes other than framing. It is still seeing the same pixels but in normal mode 2/3rds are thrown away through line-skipping with the remaining pixels brought back together. Of course, if you reposition and refocus you will have affected DOF because you moved further away from the subject. At least, that's how I understand things but it fries my brain to think about it.

yeah i am right
and you got it when you said moved further away from the subject

and that is what im talking about

that is depth of field actually

what about the lens parameters - of coz they remain the same

but to fit into crop frame you have to move further
and this is how your depth of field multiplied to eternity

and you forgetting about narrow DOP forever

[1%]

What about a wider lens than 50mm? Already a problem with a 1.6 factor so you pretty much need a superwide for this type of thing.

[Monti]

What about a wider lens than 50mm? Already a problem with a 1.6 factor so you pretty much need a superwide for this type of thing.

yeah i covered this on previous page

actually to have wide focal length doesnt help you to have narrow depth of field

coz for long focal length you need kinda any f stop value and you have good thing (beside distance)

and for wide angle - really imposible to have narrow depth of field

coz if u wana know how does this counts

lets say 50 f1.8

divide that u get around 27.5 value depth of field

now we take 18 f1.8 you get 10 value

it means not narrow at all

more the value - shallower is DOP

ps thats why i used the opposite way
and made use of this thing
by doing a super tele zoom shooting on 300 mm f5.6
guess what? the value of it is around 55

and thats even better than 50 1.8 like twice

[Andy600]

TBH the only time you need worry about this is if you shoot with a full frame camera and an APS-C and want identical shots. I never worry about it. It's too much of a headfuck. I can get very shallow DOF on an F1.4 on the 50D that's too shallow to use and impossible to keep something moving in focus.

[Supermac]

@Monti - It's a tricky concept to get your head around but DOF does not change when you punch between crop and non-crop because there is no optical difference between the two modes other than framing. It is still seeing the same pixels but in normal mode 2/3rds are thrown away through line-skipping with the remaining pixels brought back together. Of course, if you reposition and refocus you will have affected DOF because you moved further away from the subject. At least, that's how I understand things but it fries my brain to think about it.

I'm with the green cat on this one. You can't compare a crop image to the original non crop for dof because it will be the same. You need to compare the crop to a reframed full sensor image which matches the crop. To get the full sensor to match the crop you would need to get closer, use a longer lens or a combination. Both of these factors reduce dof quite a bit.

[Monti]

TBH the only time you need worry about this is if you shoot with a full frame camera and an APS-C and want identical shots. I never worry about it. It's too much of a headfuck. I can get very shallow DOF on an F1.4 on the 50D that's too shallow to use and impossible to keep something moving in focus.

if you worry about difference in depth of field between full frame and APS-C crop cameras (like canon 50d)
this is not the case

coz there you got what?

canon 5d mark iii 50 mm gives true f1.8
canon 50d 50 mm in reality gives f2.8

hey thats not bad at all!
we dont worry of it.
with 50 mm f 1.4 even better - f 2 on canon 50 d

but when you do like 5x and 10x zoom this is whole different world

now your 50 mm f1.8 is freaking f8 on x5 and f16 on x10

i will make this shots tomorrow and show you guys a real example with Nikon 50 1.8
which is known as sharpest lens on DSLR market

[Andy600]

Maybe according to Ken Rockwell it is 


...actually, I love my Nikon 50s.

[Andy600]

@1% - are you gonna take a look at the .mlv code anytime soon? I've had a play with g3gg0's module and it's slower on the 50D but having the metadata is nice.

[Monti]

BTW
i want to ask developers of magic lantern

would you do the same thing fro Nikon d7000 on raw video?

there is one guy who hacked it for raw video
but just like 1.5 fps for 10 seconds only

i think its gona be too long for him to do it alone
http://nikonrumors.com/2013/07/06/nikon-d7000-hacked-to-record-liveview-raw-video.aspx/

i ask because i have canon 50d and nikon d7000

and of coz the SD card is limited to whatever speed it is 20 mb or 40 mb

but the image quality i think it can be better than canons

[araucaria]

You are obviously not going to be able to take the same shot in crop mode as in full sensor mode with a 50 1.4, you would need a 20mm f0.56 to have the same image, I think these f stop comparsions work perfectly fine from an photograpic standpoint.

The d7000 thing is not going to happen, there is just 1 guy looking into it and they are still figuring out basic stuff on the firmwares, don't even think of being able to use the two card slots to give 40mb/s. The test he made was writing around 20mb/s so... And it was just junk, no actual images.

[1%]

@1% - are you gonna take a look at the .mlv code anytime soon? I've had a play with g3gg0's module and it's slower on the 50D but having the metadata is nice.

How much slower? I was waiting for it to hit the main tree at some point.. even HDMI plugged in makes a difference.

[Andy600]

How much slower? I was waiting for it to hit the main tree at some point.. even HDMI plugged in makes a difference.

I estimate between 15-20% slower than raw_rec with Tragic Lantern but he built it for the 5D3 afaik so maybe there are some tweaks that are needed for the 50D!?!. The code is in his repo. If you do decide to take a look can you maybe rename it so we can have both loaded for testing? There is a new build of mlv2dng too.

Does HDMI have a negative impact on performance?

[Monti]

How much slower? I was waiting for it to hit the main tree at some point.. even HDMI plugged in makes a difference.

oh btw what about HDMI tweaks for canon 50d raw video on tragic lantern side?

id rather record on external recordre like atomos ninja 2
than trying to fit in compact flash card footage that takes 4 gb per minute

[Andy600]

oh btw what about HDMI tweaks for canon 50d raw video on tragic lantern side?

id rather record on external recordre like atomos ninja 2
than trying to fit in compact flash card footage that takes 4 gb per minute

We all would but no can do! HDMI is 8bit and nowhere near the bandwidth needed for raw video.

[Monti]

The d7000 thing is not going to happen, there is just 1 guy looking into it and they are still figuring out basic stuff on the firmwares, don't even think of being able to use the two card slots to give 40mb/s. The test he made was writing around 20mb/s so... And it was just junk, no actual images.

yeah thats what im saying
i just didnt want to wait for him to do that nikon d7000 raw video

and went to buy myself a canon 50d to follow up with magic lantern guys for raw video lately

that guy will never make it alone
unless people from magic lantern would go for it and sort that out

20mb/sec isnt too bad
canon 600d is doing raw video on 20mb/sec on sd cards as well

[Monti]

We all would but no can do! HDMI is 8bit and nowhere near the bandwidth needed for raw video.

yeah then...
if i wanted 8 bit prores uncompressed HDMI output
i would buy Nikon d800 or Nikon d600

but i went to Canon 50d
coz raw video is raw video

its hollywood standart.

(ARRIRAW: 2880 x 1620, uncompressed 12 bit log without white balance or exposure index processing applied. )
http://www.arri.com/camera/digital_cameras/cameras/camera_details.html?product=8&subsection=technical_data&cHash=177d18e5da12e11481110e620f560c80

but in reality the difference here is
14 stops of dynamic range

it means dual iso in video

like the one on 5d mark 3

also the resulution is like 4 times higher means bitrate 300 mb/sec
and external hard disk for 1 tb or more

other than that - canon 50d is pretty much a hollywood camera
again - it happen thanks to magic lantern team

generally to understand what is raw video dynamic range or HDR video
for those who dont know
is when you see lots of white and black stuff on same screen
and colors are also very different filling up this space

on anything else than raw video you cant go that far
coz raw contains wide range of data between under and over exposed data from sensor

and now some fun for developers
the Matrix remake hehe

[robertgl]

Well I started testing my cam and the komputerbay 32gb CF card got corrupted. It's on its way back for a refund..
I wasn't expecting these cards to be so fragile..  What card readers do you use? 

[dlrpgmsvc]

and thats an idea Andy600!

so 18-35 f1.8 sigma lens comes into the game

first part 18 mm it is going to be 28 mm f2.8 on normal and like 85 mm f 8 on crop x5 mode 200 mm f 16 x10 mode
double it with 35 mm gives you 50 mm f2.8 on normal and 180 mm f 8 on crop x 5 and 400 mm f 16 x10 mode

Wrong. Totally. The f-number doesn't change at all with crop factor!

[dlrpgmsvc]

yeah well let me think about it...

we talking about framing the scene isnt it?

so lets say i shoot a person head

my depth of field is like from his nose to his ear

that is shallow one.

now if we zoom in in cr2 we get what?

head is choped half and we need to reframe it

when we reframe it what happens?

depth of field is not narrow anymore

now my depth of field is whole head and much more

not as shallow as it was when i frame just nose and ear

why is that?

because crop mode means 50 mm becomes 250 mm

now i have to shoot from distance not 4 meters but like 20 meters to get kinda same framing

and 20 meters gives me what? huge fat bulky depth of field that i can even bring a bus into it

p.s. of coz u dont get head shot on 50 mm from 4 meters
but u got the point

Totally wrong again. If you frame the same size object, the dof is the same at all focal lengths. http://www.cambridgeincolour.com/tutorials/depth-of-field.htm

[araucaria]

That's only true if the sensor size stays the same.