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01-14-2012, 10:54 PM - 1 Like   #151
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QuoteOriginally posted by D4rknezz Quote
Second part of the question : (derived from the first)

If say, the sweet spot for every lens is around F8 (F8 and be there), whether you own a crop or a FF, then basically, for the same given FOV, if I have a 50mm on an FF at F8, to achieve the same kind of sharpness on a Crop I would need to be at 75mm F12 or something..which means that if I had dialed F8 on the crop sensor for reasons of exposure, then I will always get a less sharper result.

Is this also correct?

In summary - an FF, given the lens that is right now out for sale, can always reach a shallower DOF, and will always be sharper at the same FOV given the same f stop.

?
No. Please stop now. Step away from the computer and take pictures. Please stop with the physics of optics and take some goddamned pictures.

Unless your only interest in photography is gearfaggotry, it doesn't really matter. What can possibly be that important that you need to figure precise calculations to make something look similar to another system?

Just go out and buy a full frame camera and be done with it.

01-14-2012, 11:08 PM   #152
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QuoteOriginally posted by alohadave Quote
Perspective has nothing to do with how much the image is cropped. It is solely from the distance from the camera to the subject. Cropping an image does not change your perspective.
Thanks, I must have wasted 4 years at art school when I should've just deferred to your better understanding.

Linear Perspective is a direct product of FOV and the size of the image projection in relation to the viewer. IMO the human element defines the true nature of the differences here and not just the hardware. COC is also affected by pixel size, which in turn, is determined by format at the moment so there is that to consider a bit.

I think that people asking for equivalence (like myself) tend to be those who've only used film bodies in the past and have that as their frame of reference. Just because many others have only known APS-C doesn't mean that the questions those people have are irrelevant to others on the forum.

PS: All of this argument would be moot if you could actually see the lens output in the VF. These days, focusing the image is a bit of gamble in itself due to the focusing screens for one thing.

Last edited by bossa; 01-14-2012 at 11:22 PM.
01-14-2012, 11:37 PM   #153
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Eh, I do take pictures. Not as many as you do, I know. But also not the style or the shots that you are doing either. I am focusing on portraits/weddings/models - I barely take any landscape or building or structure or colours or else.

Obviously, at this moment I believe that what is possibly that important is a shallow dof while maintaining sharpness on 2 subjects holding each other's gaze. I need to know what the 7 thousand dollar wedding guy does that makes his picture just that different in dof than I do, and makes his work consistently pop more even with subtle photoshopping. I am trying to rule out or consider every possibilities - including blurring in software, or simply knowing the location where the background is 100 feet away from the subjects. I love my pentax, and I dont
have money for an FF....unless the difference is going to be paid by the weddings I do.

If i had the money to simply go and buy the system, i would. As it is, I need to know the logic behind this. I understand that the photographer makes the picture, and not the system.
However, given the picture I wish to take, if a photographer has BOTH system, which camera would they grab?

If gearfaggotry, as you say it, is my sole reason, I am not going to be using pentax at all.

Now, did you mean NO as the answer to both my questions, or did you mean no as please dont ask ? If its the first, I need to have a better explanation than a simple no. If its the latter, then well, I did direct my question to Jsherman - but I can ask him in private if you so wish.






QuoteOriginally posted by alohadave Quote
No. Please stop now. Step away from the computer and take pictures. Please stop with the physics of optics and take some goddamned pictures.

Unless your only interest in photography is gearfaggotry, it doesn't really matter. What can possibly be that important that you need to figure precise calculations to make something look similar to another system?

Just go out and buy a full frame camera and be done with it.
01-14-2012, 11:52 PM   #154
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QuoteOriginally posted by alohadave Quote
No. Please stop now. Step away from the computer and take pictures. Please stop with the physics of optics and take some goddamned pictures.

Unless your only interest in photography is gearfaggotry, it doesn't really matter. What can possibly be that important that you need to figure precise calculations to make something look similar to another system?

Just go out and buy a full frame camera and be done with it.

FWIW, I take thousands and thousands of shots - and I also like to know about the physics of optics, and know about things like equivalence, and lots of other stuff. One can multitask, in life, after all. (also, check the thread title! It's not post your photos )

.

01-14-2012, 11:57 PM   #155
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QuoteOriginally posted by bossa Quote
Thanks, I must have wasted 4 years at art school when I should've just deferred to your better understanding.

Linear Perspective is a direct product of FOV and the size of the image projection in relation to the viewer. IMO the human element defines the true nature of the differences here and not just the hardware. COC is also affected by pixel size, which in turn, is determined by format at the moment so there is that to consider a bit.
I don't know what they taught you, or what you learned, but that is not what I'm talking about. If I stand 10 feet from a person, my perspective does not change if I crop the picture from one lens or use two different lenses.

I don't really care about the circle of confusion. It doesn't relate to my perspective. Pixel size has no impact on where I am standing when I take a picture. In addition, the FoV doesn't change your perspective unless you are moving to make the subject the same size, in which case your perspective must change because you've changed position. Why you would even raise CoC and pixel size when discussing perspective confuses the hell out of the topic.

QuoteQuote:
I think that people asking for equivalence (like myself) tend to be those who've only used film bodies in the past and have that as their frame of reference. Just because many others have only known APS-C doesn't mean that the questions those people have are irrelevant to others on the forum.
It doesn't make them irrelevant, but it sure makes you seem to want to argue the differences ad infinitum.
01-15-2012, 12:10 AM   #156
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QuoteOriginally posted by D4rknezz Quote
J,

I'd like to see if my understanding here of the little paragraph joseph wrote is correct. In Summary,

1. One can theoretically calculate the equivalent focal length required for say, a Pentax K5 lens to achieve the same shallow DOF as a 5D MK2. This is the reason for the argument that the DOF of FF isnt superior than a Crop sensor.
Yes. There is no native 'superiority' that comes from the format with regards to be able to achieve a particular FOV/DOF combo.

QuoteQuote:
2. However, the actual lens required to have the same shallow dof and fov may not exist on the crop sensor format, if one hunts for shallow DOF only.
Exactly. It's, as Falk pointed out in a good thread last year, really all about the lenses available after all.

QuoteQuote:
For example, if our 50-135 2.8 is roughly the fov for an FF 70-200 2.8, the same can not be said if I were to look for the equivalent DOF, because at 150mm i would need it to be a f2 to give me the same DOF. And since there isnt any zoom lens f2, for all intend and purposes, if shallow DOF is what I am looking for, a FF format is what I need.
Yes, but it would be closer to an f/1.8 zoom. Also, it's not just about looking for the shallowest DOF possible - consider being able to retain the aps-c f/2.8 DOF on the zoom, while gaining f/4.5 sharpness on the focal plane. (any f/2.8 zoom made today is going to be sharper at f/4.5 than wide-open at f/2.8. On FF you can stop it down to f/4.5 and still get that nice f/2.8 subject isolation - if that's what you happen to be after,)



QuoteQuote:
Second part of the question : (derived from the first)

If say, the sweet spot for every lens is around F8 (F8 and be there), whether you own a crop or a FF, then basically, for the same given FOV, if I have a 50mm on an FF at F8, to achieve the same kind of sharpness on a Crop I would need to be at 75mm F12 or something..which means that if I had dialed F8 on the crop sensor for reasons of exposure, then I will always get a less sharper result.
Not entirely sure I understand the question, but if you're asking "do i need to stop the 75mm on FF down to f/12 to match the DOF a 50mm at f/8 would bring", then yes. Also, yes, it's likely that a 50mm at f/8 is going to be sharper than some 75mm at f/11, although I doubt the difference would really be noticeable.


QuoteQuote:
In summary - an FF, given the lens that is right now out for sale, can always reach a shallower DOF, and will always be sharper at the same FOV given the same f stop.
Hmmm, actually the lenses should show the same sharpness when shot at the same aperture on both formats. There is no attribute described by equivalence that would change that. The FF image may appear sharper because the aps-c image is effectively enlarged more, showing any lens defects more clearly, but that's probably not what you were asking.

The lens-related way FF can bring a sharper image is that you can sometimes maintain a 'high-aperture' DOF look while stopping down 1.3 stops to gain more sharpness on the focal plane.

Last edited by jsherman999; 01-15-2012 at 12:32 AM.
01-15-2012, 12:11 AM   #157
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Wait, i got confused there. I meant, if I have an FF at 75 mm at F5.6 to achieve sharpness, then to achieve the same kind of DOF on crop i would need to have 50mm at f3.5.....
So ..if a smaller aperture is always a sharper image, then the FF at 5.6 will be sharper than the 50 at 3.5?




QuoteOriginally posted by D4rknezz Quote
J,


Second part of the question : (derived from the first)

If say, the sweet spot for every lens is around F8 (F8 and be there), whether you own a crop or a FF, then basically, for the same given FOV, if I have a 50mm on an FF at F8, to achieve the same kind of sharpness on a Crop I would need to be at 75mm F12 or something..which means that if I had dialed F8 on the crop sensor for reasons of exposure, then I will always get a less sharper result.

Is this also correct?

In summary - an FF, given the lens that is right now out for sale, can always reach a shallower DOF, and will always be sharper at the same FOV given the same f stop.

?
01-15-2012, 12:21 AM   #158
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Ah Okay, i think i got this. Sorry, my second part of the question i mixed up FF and Crop calculation but i see you understood what i meant. So basically, since I do care about very shallow DOF for my kind of pictures, then i am hoping for pentax to release F/1.8 zoom lenses. Cuz I dont think I can afford an FF yet.

Thanks for the explanation J.




QuoteOriginally posted by jsherman999 Quote
Yes. There is no native 'superiority' that comes from the format with regards to be able to achieve a particular FOV/DOF combo.



Exactly. It's, as Falk pointed out in a good thread last year, really all about the lenses after all.



Yes, but it would be closer to an f/1.8 zoom. Also, it's not just about looking for the shallowest DOF possible - consider being able to retain the aps-c f/2.8 DOF on the zoom, while gaining f/4.5 sharpness on the focal plane. (any f/2.8 zoom made today is going to be sharper at f/4.5 than wide-open at f/2.8. On FF you can stop it down to f/4.5 and still get that nice f/2.8 subject isolation - if that's what you happen to be after,)





Not entirely sure I understand the question, but if you're asking "do i need to stop the 75mm on FF down to f/12 to match the DOF a 50mm at f/8 would bring", then yes. Also, yes, it's likely that a 50mm at f/8 is going to be sharper than some 75mm at f/11, although I doubt the difference would really be noticeable.




Hmmm, actually the lenses should show the same sharpness when shot at the same aperture on both formats. There is no attribute described by equivalence that would change that. The FF image may appear sharper because the aps-c image is effectively enlarged more, showing any lens defects more clearly, but that's probably not what you were asking.

The lens-related way FF can bring a sharper image is that you can sometimes maintain a 'high-aperture' DOF look while stopping down 1.3 stops to gain more sharpness on the focal plane.


01-15-2012, 12:27 AM - 1 Like   #159
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QuoteOriginally posted by D4rknezz Quote
Wait, i got confused there. I meant, if I have an FF at 75 mm at F5.6 to achieve sharpness, then to achieve the same kind of DOF on crop i would need to have 50mm at f3.5.....
So ..if a smaller aperture is always a sharper image, then the FF at 5.6 will be sharper than the 50 at 3.5?
Well, keep in mind that the level of sharpness is always going to be lens-dependent also. For example, a variable-aperture 28-300 at 75mm f/5.6 is probably not going to be as sharp in the center as say the M 50 f/1.7 stopped down to f/3.5

But you have the theory correct. Following through, you'll see that any 'advantage' FF may have in the high aperture, wide-to-mid telephoto realm kinda reverses at around 300mm, where aps-c starts to make a lot of sense if you discount cropping on FF.
01-15-2012, 02:19 AM   #160
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QuoteOriginally posted by alohadave Quote
If I stand 10 feet from a person, my perspective does not change if I crop the picture from one lens or use two different lenses..
Like I said earlier, it's relative to scale and viewing distance. If you crop out some information and enlarge the output then the relationship to the viewer changes because there's a different context and scale of reference. I won't bother to respond to your remarks re' my education or competency.
01-15-2012, 08:13 AM - 1 Like   #161
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QuoteOriginally posted by jsherman999 Quote
FWIW, I take thousands and thousands of shots - and I also like to know about the physics of optics, and know about things like equivalence, and lots of other stuff. One can multitask, in life, after all. (also, check the thread title! It's not post your photos ).
SAME!

I may have hit a million photo's in my archive. But I still love and enjoy learning about the technology.
01-15-2012, 10:23 AM   #162
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Mika...to use an old cliche', you are comparing apples and oranges. 35mm film will always have a different look than digital. It doesn't matter if the digital is full frame, APS-C, medium format or micro 4/3. Film is a physical medium where digital is 1's and 0's. The two will never look the same.
01-15-2012, 10:48 AM   #163
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QuoteOriginally posted by alohadave Quote
I don't know what they taught you, or what you learned, but that is not what I'm talking about. If I stand 10 feet from a person, my perspective does not change if I crop the picture from one lens or use two different lenses.

.
This a common mistake. Linear perspective comes from a ratio of object distances--you can two picture at two different object distances and achieve the same linear perspective. Since we think of an image as one thing, what is foreground and background changes when you change focal length or crop. Since the ratio of foreground to background distance changes, so does the perspective of the image--landscapes have very different perspectives because of focal length simply because of that. (The ratio of objects in the frame do not change, but a picture is more than some arbitrary choice of objects, but you still can change distance to those same objects and maintain the same perspective or image size ratio and so this is a relative problem, not and absolute one.)

The other way to think of this is that the focal length or crop changes the final magnification of the image--we think of display size is constant. In two point perspective, displacing the points changes perspective. Change in magnification has the same effect.

The great thing is, you can actually see this effect in your photography.
01-15-2012, 11:09 AM   #164
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QuoteOriginally posted by Yamanobori Quote
This a common mistake. Linear perspective comes from a ratio of object distances--you can two picture at two different object distances and achieve the same linear perspective. Since we think of an image as one thing, what is foreground and background changes when you change focal length or crop. Since the ratio of foreground to background distance changes, so does the perspective of the image--landscapes have very different perspectives because of focal length simply because of that. (The ratio of objects in the frame do not change, but a picture is more than some arbitrary choice of objects, but you still can change distance to those same objects and maintain the same perspective or image size ratio and so this is a relative problem, not and absolute one.)

The other way to think of this is that the focal length or crop changes the final magnification of the image--we think of display size is constant. In two point perspective, displacing the points changes perspective. Change in magnification has the same effect.

The great thing is, you can actually see this effect in your photography.
I understand focal length here (which compresses or expands space perpendicular to the film plane), but not crop. Cropping doesn't change the distances (or apparent distances) between anything. Just more or less stuff is visible.
01-15-2012, 11:12 AM   #165
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QuoteOriginally posted by Yamanobori Quote
This a common mistake. Linear perspective comes from a ratio of object distances--you can two picture at two different object distances and achieve the same linear perspective. Since we think of an image as one thing, what is foreground and background changes when you change focal length or crop. Since the ratio of foreground to background distance changes, so does the perspective of the image--landscapes have very different perspectives because of focal length simply because of that. (The ratio of objects in the frame do not change, but a picture is more than some arbitrary choice of objects, but you still can change distance to those same objects and maintain the same perspective or image size ratio and so this is a relative problem, not and absolute one.)

The other way to think of this is that the focal length or crop changes the final magnification of the image--we think of display size is constant. In two point perspective, displacing the points changes perspective. Change in magnification has the same effect.

The great thing is, you can actually see this effect in your photography.
I don't believe you, but if you can show me two pictures taken from two different positions that show the same perspective, I'll not comment on it again.
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