Canon Cine Primes kit or CP.2 ?

[Nick Morrison]

I'm sorry if I've misunderstood your post, but this is not true. The reason why medium format lenses don't get any faster than f/2.0 is not because they cannot. Rather, it's because of size and cost limitations. And personally - I shoot Sony NEX and Nikon FX cameras - let me tell you, I don't want anything wider than f/2.8, especially if you're talking about focal lengths over, say, 100mm.

I'm not sure you're right. I've always assumed that image circle did have an affect on illumination. Of course anything is possible, but by and large they seem to be related. Otherwise how else to explain the incredible speed of 16mm lenses, and the relative slowness of Medium Format and Anamoprhic glass? Clearly, there seems to be a correlation between image circle and exposure.

Otherwise, how else to explain also why there's NO FULL FRAME wide that is an F2 or faster? (I mean at 18mm or wider). I'm sure it's possible, but at a price mortals can afford?

Obviously an experienced lens tech needs to weigh in here, but I've always assumed there was a mathematical relationship between image circle and exposure, just as there is for image circle and depth of field.

[BRANDON JAMESON]

HAHA good one.
Actually, I'm working-and- when I'm working good things happen....

Jacek makes GREAT things happen!!!

[Karim D. Ghantous]

Clearly, there seems to be a correlation between image circle and exposure.

Yes. But only because:

I'm sure it's possible, but at a price mortals can afford?

So we agree, pretty much. :-) Of course only a physicist or optical engineer can give an authoritative comment.

just as there is for image circle and depth of field.

What do you mean here? I'm about to disagree with you again!! :-P

[paul ross jones]

I'm sorry if I've misunderstood your post, but this is not true. The reason why medium format lenses don't get any faster than f/2.0 is not because they cannot. Rather, it's because of size and cost limitations. And personally - I shoot Sony NEX and Nikon FX cameras - let me tell you, I don't want anything wider than f/2.8, especially if you're talking about focal lengths over, say, 100mm.

yeah, its mainly just cost limiting the f-stop of a medium format lens-

check out this f1.3 250mm 6x6 hasselblad lens-

http://www.ebay.com/itm/230649811001...84.m1438.l2649





i would love to see what the images look like with this.


paul

[Mitch Gross]

Which molecule would you like in focus?

[Nick Morrison]

"just as there is for image circle and depth of field."
What do you mean here? I'm about to disagree with you again!! :-P

There is a correlation between image circle and depth of field. The smaller the image circle the deeper the depth of field. And the larger the image circle, the shallower the depth of field. What I'm about to say is really rough math, but it is said that S35 film looks approximately two stops MORE SHALLOW than 16mm. And in turn, full frame (ie "5D") looks two stops MORE SHALLOW than S35. That's why the 5D is known for being so "shallow". That's also why the RED MX sensor, which is slightly larger than S35, can give you a bit more shallow look than traditional film.

Medium Format, being twice the size of full frame 5D, is very likely two stops shallower still.

[Matt Gottshalk]

Which molecule would you like in focus?

Yeah pretty much.

[Karim D. Ghantous]

There is a correlation between image circle and depth of field. The smaller the image circle the deeper the depth of field. And the larger the image circle, the shallower the depth of field. What I'm about to say is really rough math, but it is said that S35 film looks approximately two stops MORE SHALLOW than 16mm. And in turn, full frame (ie "5D") looks two stops MORE SHALLOW than S35. That's why the 5D is known for being so "shallow". That's also why the RED MX sensor, which is slightly larger than S35, can give you a bit more shallow look than traditional film.

Medium Format, being twice the size of full frame 5D, is very likely two stops shallower still.

I don't want to sound like a troll but you're incorrect again. :-P The reason why DOF in 16mm is deeper than in 35mm is not because of image circle, but because of the relationship of focal length to FOV.

To get a 40° FOV on a 4-perf 35mm frame requires, say, a 25mm lens (very roughly). To get a 40° FOV on a 16mm camera would require, say, a 12mm lens. Assuming equivalent settings (distance and aperture), the 12mm lens would have more DOF by virtue of being shorter than the 25mm, not by having a smaller image circle.

I'm happy to be corrected by an engineer, but I'd be very surprised if I were mistaken. Not that there's anything wrong with being wrong.

[Nick Morrison]

I don't want to sound like a troll but you're incorrect again. :-P The reason why DOF in 16mm is deeper than in 35mm is not because of image circle, but because of the relationship of focal length to FOV.

To get a 40° FOV on a 4-perf 35mm frame requires, say, a 25mm lens (very roughly). To get a 40° FOV on a 16mm camera would require, say, a 12mm lens. Assuming equivalent settings (distance and aperture), the 12mm lens would have more DOF by virtue of being shorter than the 25mm, not by having a smaller image circle.

I'm happy to be corrected by an engineer, but I'd be very surprised if I were mistaken. Not that there's anything wrong with being wrong.

I'm willing to be stand corrected, and everything you say makes sense.

But...please explain then why a 25mm 2.8 will look MUCH MORE SHALLOW on a 5D than a 7D? I've been told by every DP I've worked with on these cameras that it's because the sensor on the 5D is LARGER (ie...can read a larger image circle). In this particular scenario, the 5D not only sees a larger FOV, but it also noticeably more shallow? Why?

[Alan Peterson]

There really shouldn't be any difference in the depth of field. The situation you're describing is comparable to cropping an image in post except with respect to resolution. Changing the area from the sensor that you're grabbing the image from doesn't change the depth of field.

Likely what the other DPs are referring to is that to get the same angle of view on the 5D, you're using longer lenses and consequently have a shallower DoF.