lewdoglewdog wrote:
The standard focusing screen for the 5D (and I believe all lower cameras in Canon's line-up) shows a dof of f/4. The S versions show a dof of 1.8. This is directly from a "Tech Tips" or whatever it's called that Chuck Westfall wrote.
Then Canon should fire Chuck Westfall, because that is the most moronic thing I have ever heard about focusing screens.
cogitech wrote:
Then Canon should fire Chuck Westfall, because that is the most moronic thing I have ever heard about focusing screens.
Can you explain why you say that? I'm not disagreeing, I just don't know. Since the S series shows an obviously shallower dof, it would seem to make sense that you could quantify the difference.
Just to clarify, the two series of screens I'm referring to are the Ex-A Standard Precision Matte and the Ex-S Super Precision Matte, with the Ex-A being what comes with the 5D2 and all lower Canons. I phrased it like that because I don't know which screens the 1D/1DS cameras come with. I hope it didn't come off like I was saying that the cameras themselves only showed f/4 dof, but rather that the stock screens did.
Focusing screens do not have a DoF. That is ridiculous.
The truth of the matter is that the A screens are optimized for brightness rather than accuracy, and as such they do not accurately depict the plane of focus at apertures of f2.8 and larger. The S type screens are optimized for accuracy, and as such they depict the plane of focus more accurately at all apertures, but they are particularly more accurate than the A screens at larger apertures (from 2.8 all the way to f1.2), where the A screens are perfectly useless. This optimization for accuracy in the S type screen sacrifices brightness to some extent, which becomes more apparent with lenses f4 and slower, but still remains entirely usable at smaller apertures (unlike split-prism, which tend to "black out") as long as light levels are good enough.
To say that the A screen has a "DoF" of f4 and the S screen has a "DoF" of f1.8 is, quite frankly, simplistic, misleading, inaccurate, and just plain stupid. Chuck should be ashamed of himself.
cogitech wrote:
Focusing screens do not have a DoF. That is ridiculous.
The truth of the matter is that the A screens are optimized for brightness rather than accuracy, and as such they do not accurately depict the plane of focus at apertures of f2.8 and larger. The S type screens are optimized for accuracy, and as such they depict the plane of focus more accurately at all apertures, but they are particularly more accurate than the A screens at larger apertures (from 2.8 all the way to f1.2), where the A screens are perfectly useless. This optimization for accuracy in the S type screen sacrifices brightness to some extent, which becomes more apparent with lenses f4 and slower, but still remains entirely usable at smaller apertures (unlike split-prism, which tend to "black out") as long as light levels are good enough.
To say that the A screen has a "DoF" of f4 and the S screen has a "DoF" of f1.8 is, quite frankly, simplistic, misleading, inaccurate, and just plain stupid. Chuck should be ashamed of himself.
In all fairness, I've been searching my pants off since your first reply in order to find where he stated that. I simply can not find it. So-there's a chance I'm remembering inaccurately. Sorry for derailing the thread.
My slowest lens is f/4, so the ee-s for my 5dmk2 would make a world of difference when I try to manual focus? I know I stated that the the stock -s screens are only good if you shoot 1.4 or faster, but that's not from my experience becaue I don't have any experience...I'm just passing information along. And no, I'm not affiliated with anyone here or elsewhere trying to sell screens. I just got my 5DMK2 about 5 months ago and I like taking 1:1 macro photography using the Canon EF 100mm f/2.8 Macro USM lens (hopefully at 1:1 it's aparent focusing aperture is 2.8) and now I'm starting to use older MF lenses at the 1.4 range.
Quite honestly I'm just surfing for information and looking back maybe I should have explained in more detail where/how I was getting my information. Just FYI, I checked yesterday and US Amazon had only one Rokinon left...it's gone now until restock. I just fear the demand from discussions such as this will raise the price next go-around.
lewdoglewdog wrote:
In all fairness, I've been searching my pants off since your first reply in order to find where he stated that. I simply can not find it. So-there's a chance I'm remembering inaccurately. Sorry for derailing the thread.
Then I owe a pre-emptive apology to Chuck, if that is the case, and an apology to anyone out there unfortunate enough to have ever thought a focusing screen has DoF. I should not be so critical of people who do not understand. I simply hate seeing misinformation like this being perpetuated.
Perhaps what he meant was the A screen is akin to f/4 in it's ability to show the eye a difference in focus and out of focus areas. Where as the S screen has the ability to show the eye a thinner DOF akin to a f/1.8 lens..
Maybe it was just a way to explain in simple terms what they appear to do for you when placed in the camera.
As they do APPEAR to do that, in a sense...
If I were to explain focusing screens to someone without technical knowledge then I'd probably explain it in similar terms, though I'd make sure I'm telling them that thats how they will feel, not what's actually physically taking place.
Maybe when Chuck wrote it (if he wrote it), he was writing it with that meaning in mind.
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Canon VS Rokinon - I really think the canon is a good value for the money, and I think they're both very similar lenses, so much so that you'd probably have to really ask yourself is a slight edge in image quality/1.4 (rokinon) worth the loss of AF... When I used the canon, I used AF... If you don't need AF, consider the rokinon!
I just picked up the 85 ZE and I have a lot of shooting to do with it, but I feel it's worth having over the 85L II even though the 85L II has AF and is slightly sharper.. So really it depends on your shooting needs and shooting style.
cogitech wrote:
To say that the A screen has a "DoF" of f4 and the S screen has a "DoF" of f1.8 is, quite frankly, simplistic, misleading, inaccurate, and just plain stupid.
No one said that. The real quote was that the stock screen shows a (shortest) DOF of f/4 and the EE-S screen shows f/1.8. That makes sense and is true. Anyone having changed their screen should have noticed it.
A screen optimized for manual focus is "grainier", which means it lets you see light falling onto it from flatter angles ( = larger apertures). At the same time, the viewfinder will grow darker, since less light is transmitted through the screen.
This is the reason for the stock screens being inferior for manual focusing. They are optimized for brightness, not DOF preview.
cogitech wrote:
So, you are saying that when I use an f4 lens with my Ee-S screen, I am seeing "f1.8 DoF"?
Hogwash!
And, likewise, when I use an f1.2 lens with my Ee-S screen I am seeing "f1.8 DoF"?
More hogwash!
My thinking (before your replies made me start really questioning my understanding) is that the screens would show the dof down to the maximums (i.e. 4 vs. 1.8). So, with an S screen, the 4 lens would look like 4, but the 1.2 lens would look like 1.8. In other words, the screens just can't show a shallower dof than the 4 or 1.8 characteristic, but do show the true dof at apertures at or higher than that.
cogitech wrote:
So, you are saying that when I use an f4 lens with my Ee-S screen, I am seeing "f1.8 DoF"?
No.
And, likewise, when I use an f1.2 lens with my Ee-S screen I am seeing "f1.8 DoF"?
Yes.
Edit: Try the stopdown preview button. You will not see any difference in DOF from f/1.2 to ~f/2 with your EE-S sceen. Only a difference in luminance. With the stock screen, you'll get the same DOF in the viewfinder from f/0 to f/4. That's why it's useless for manual focusing with fast lenses.
lewdoglewdog wrote:
My thinking (before your replies made me start really questioning my understanding) is that the screens would show the dof down to the maximums (i.e. 4 vs. 1.8). So, with an S screen, the 4 lens would look like 4, but the 1.2 lens would look like 1.8. In other words, the screens just can't show a shallower dof than the 4 or 1.8 characteristic, but do show the true dof at apertures at or higher than that.
Now you've said it much better than Chuck (and anyone else in this thread).
Edit: Try the stopdown preview button. You will not see any difference in DOF from f/1.2 to ~f/2 with your EE-S sceen. Only a difference in luminance. With the stock screen, you'll get the same DOF in the viewfinder from f/0 to f/4. That's why it's useless for manual focusing with fast lenses.
The "f1.8" is what I question. If that was the case, then I would have difficulty achieving critical focus at f1.2, and I don't.
cogitech wrote:
To say that the A screen has a "DoF" of f4 and the S screen has a "DoF" of f1.8 is, quite frankly, simplistic, misleading, inaccurate, and just plain stupid.
Makten wrote:
No one said that. The real quote was that the stock screen shows a (shortest) DOF of f/4 and the EE-S screen shows f/1.8. That makes sense and is true. Anyone having changed their screen should have noticed it.
A screen optimized for manual focus is "grainier", which means it lets you see light falling onto it from flatter angles ( = larger apertures). At the same time, the viewfinder will grow darker, since less light is transmitted through the screen.
This is the reason for the stock screens being inferior for manual focusing. They are optimized for brightness, not DOF preview.
So I assume the Maxwell treated screen is supposed to transmit more light while at the same time maintaining a true, accurate representation of the lenses aperture?
If I got anything wrong in that statement, then please correct me in such a way as to not get the thread locked.
"Only 1 left in stock--order soon.
5 new from $248.95"
Don't know in this particular case, but in general this would mean that
Amazon itself has one in stock, but that it and four other sellers all
offer new Rokinons, with the lowest-cost seller offering it for $248.95
lewdoglewdog wrote:
My thinking (before your replies made me start really questioning my understanding) is that the screens would show the dof down to the maximums (i.e. 4 vs. 1.8). So, with an S screen, the 4 lens would look like 4, but the 1.2 lens would look like 1.8. In other words, the screens just can't show a shallower dof than the 4 or 1.8 characteristic, but do show the true dof at apertures at or higher than that.
That's the apparent effect.. The exact number's are speculative as it's not something that can be measured in terms of fstops (as Fstops being used to calculate DOF are also subjective to lens FL, and distance to subject etc, so it's a stupid way of getting a accurate measurement). So in a sense as I mentioned above, it's a good way to explain the difference between the screens, for someone who understands basic photography terms. But it isn't a correct statement because you can't calculate something based on a subjective measuring system.
