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11-16-2012, 03:40 AM   #16
arv
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QuoteOriginally posted by SyncGuy Quote
Hi, i've just spotted this and i am thinking whether this is true.
I thought that a longer FL would "stretch" the background further, therefore larger, as compared to one from a shorter FL?

What happens is that the background and the foreground subject size will differ between the 2 sensor sizes due to the similarity in composition but with a change in camera distance, right?
I'd second, that perspective is a matter of the distance between camera and subject, and it doesn't matter which format or lens will be used (that will change field of view). Check these examples.
On topic - I have both DA*55 and 70mm, and in short - for portraits DA*55 is better.

Regards,
A.

11-16-2012, 04:02 AM   #17
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QuoteOriginally posted by SyncGuy Quote
Hi, i've just spotted this and i am thinking whether this is true.
I thought that a longer FL would "stretch" the background further, therefore larger, as compared to one from a shorter FL?

What happens is that the background and the foreground subject size will differ between the 2 sensor sizes due to the similarity in composition but with a change in camera distance, right?
I'm not quite sure I get what you're saying here, but let me try to explain the fundamentals of perspective in this example:

- You have two exactly identical statues, Statue 1 is placed 10 feet away, Statue 2 placed at 20 feet. In this arrangement, Statue 2 will appear to be half the size of Statue 1 even though they are actually the same size.

- Step back 10 feet. The Statue 2 will now be at 30 feet, and will appear to have shrunk by 33%. The Statue 1 is now at 20 feet and appears to have shrunk by 50%. Statue 2 now appears to be 2/3 the size of Statue 1, rather than the original 1/2. The further away you go, the closer the two statues will look in size (the ratio of apparent size approaches 1:1).

- Go back to start and do the reverse: step forward 5 feet. The Statue 1 is now at 5 feet, and appears to have increased in size by 100%. The Statue 2 is now at 15 feet and appears to have increased in size by 33%. Statue 1 now appears to be 3x the size of Statue 2, rather than the original 2x. The closer you get to Statue 1, the bigger it will look compared to Statue 2.

This is simple geometry, and is a universal concept. Focal length, sensor size and whatnot has no effect on any of this. You don't even need a camera, just see for yourself with your own eyes.

To prove that focal length has no effect on perspective, there's a simple test you can try: Put the camera on a tripod, use a 50mm lens and shoot a certain scene centered on a particular subject. Now do not move the camera, use a 100mm lens and shoot centered on the same subject. Do a 2x crop with the 50mm shot. Besides a difference in DOF, the two results will look exactly the same!

The so-called "telephoto/wide-angle perspective distortion" is nothing more than the result of you being at different distances to get the same primary subject size with each, further away with narrower angles ("telephoto"), and closer with wide angles. They look strange because it is hard to judge size and distance when the angle of view is very different from your own eyes' central focus area.

Last edited by Cannikin; 11-16-2012 at 05:32 AM.
11-16-2012, 06:01 AM   #18
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Anyway, back on topic...

I own the DA* 55, and I briefly owned the DA 70 as well (I ended up returning it). While the 70 is a cool lens, and very sharp, I wasn't a big fan of the bokeh. A bit too busy looking when it came to high contrast highlights, especially close to the plane of focus. I really like the 55's bokeh, especially around f/2 (f/1.4 can look a bit iffy).

On the other hand, the 55 is rather slow to autofocus, and not particularly accurate either, so it's not ideal for shooting moving kids for instance. The 70 is much faster.
11-16-2012, 06:17 AM   #19
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Sandy, Ok so I appreciate your comments on comparing the FA 77 vs the DA*55. I get the impression that the FA 77 is a better lens, however, there are some well respected people on this site that seem to suggest that they would rather have the DA*55 than the FA 77. I suppose that should be a whole other thread. Now, with that said, I was under the impression that the DA*55 can be had for ~$600-650 if you order over the phone, hence that is why I was just considering the DA 70 or the DA*55. I really want the FA 77, shoot don't make me rehash this all over again. My wife doesn't mind because I am so indecisive that I don't wind up buying a lens because I can't make up my mind.....and she is fine with that!

11-16-2012, 06:19 AM - 1 Like   #20
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cannikon
Thanks for your explanation on perspective. When I plot all my photo stats, I see that my most used FL is 55 mm, but that is because I have the kit lens and the 55-300. This tells me that I have the wrong lens on most of the time I do like the 55mm length for indoor shooting.
11-16-2012, 12:10 PM   #21
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One other idea is if you really want the 77, get that for now, then get one of the cheaper options in the 50mm range later. You can get the DA 50/1.8, F/FA 50/1.7 or F/FA 50/1.4 all for $250 or less. I love my FA 50/1.4 set to f/2.2 for indoor portraits.
11-16-2012, 02:07 PM   #22
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Up until recently I owned both, but just sold the 70mm. I bought the 70 after the 55, having convinced myself that even if the difference in focal lengths was subtle it was worth having both. It turns out that in my relatively unskilled hands the difference was so small that one or the other was going to be redundant, and the 55 won out. To my eye I found 'short tele' a lot more useful and useable than 'slightly less short' tele, both for shooting people and landscapes.
11-16-2012, 09:31 PM   #23
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QuoteOriginally posted by Cannikin Quote
I'm not quite sure I get what you're saying here, but let me try to explain the fundamentals of perspective in this example:

- You have two exactly identical statues, Statue 1 is placed 10 feet away, Statue 2 placed at 20 feet. In this arrangement, Statue 2 will appear to be half the size of Statue 1 even though they are actually the same size.

- Step back 10 feet. The Statue 2 will now be at 30 feet, and will appear to have shrunk by 33%. The Statue 1 is now at 20 feet and appears to have shrunk by 50%. Statue 2 now appears to be 2/3 the size of Statue 1, rather than the original 1/2. The further away you go, the closer the two statues will look in size (the ratio of apparent size approaches 1:1).

- Go back to start and do the reverse: step forward 5 feet. The Statue 1 is now at 5 feet, and appears to have increased in size by 100%. The Statue 2 is now at 15 feet and appears to have increased in size by 33%. Statue 1 now appears to be 3x the size of Statue 2, rather than the original 2x. The closer you get to Statue 1, the bigger it will look compared to Statue 2.

This is simple geometry, and is a universal concept. Focal length, sensor size and whatnot has no effect on any of this. You don't even need a camera, just see for yourself with your own eyes.

To prove that focal length has no effect on perspective, there's a simple test you can try: Put the camera on a tripod, use a 50mm lens and shoot a certain scene centered on a particular subject. Now do not move the camera, use a 100mm lens and shoot centered on the same subject. Do a 2x crop with the 50mm shot. Besides a difference in DOF, the two results will look exactly the same!

The so-called "telephoto/wide-angle perspective distortion" is nothing more than the result of you being at different distances to get the same primary subject size with each, further away with narrower angles ("telephoto"), and closer with wide angles. They look strange because it is hard to judge size and distance when the angle of view is very different from your own eyes' central focus area.
Hmm.. Thank you for the explanation!

I understand that the above explanation is provided in view of the subject in the photo. I'm saying about the background size in relation to the subject within the same composition.

Hmm...

11-16-2012, 10:35 PM   #24
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QuoteOriginally posted by icywindow Quote
I've owned both, and my opinion is that the DA* 55 renders more pleasing to me than the DA 70. If you plan on using the lenses on the 2.8 or wider aperture end of the range, the DA* 55 is stunning. The circular blades do a pretty good job of preserving the circular highlight bokeh. If you want resolution stopped down, the DA 70 delivers just a bit more than the DA* 55. But out of the two, if I were stranded on a desert island with only one of those two lenses, the DA* 55 would be my choice.

If you were stranded on a desert island, you would be shooting few portraits. I'd opt for the DA70 and it's superb stopped-down performance, especilly if I also had a DA40.
11-16-2012, 10:42 PM   #25
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55mm is fine for portraits of children and adults with fairly flat faces. 70mm would give more pleasing perspective of angular faces. If you want to understand portraits, look at portrait painting from the renaissance forward. These are the people who did a lot of serious looking at heads.
11-16-2012, 11:08 PM   #26
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QuoteOriginally posted by SyncGuy Quote
Hmm.. Thank you for the explanation!

I understand that the above explanation is provided in view of the subject in the photo. I'm saying about the background size in relation to the subject within the same composition.

Hmm...
No problem, but it seems I need to clarify:

My example does not have to do with a "subject". The "subject" is entirely the opinion of the viewer. What is the subject in my scenario? Is it Statue 1? Statue 2? A person standing between the statues? A random bird sitting on Statue 2's head? I don't know. I didn't give a subject because that is not relevant to the geometric concept.

Perspective is an geometric reality that is not subject to interpretation, and 100% determined by the position of the viewpoint. Nothing to do with focal lengths, subjects or even cameras. It just is.

You have two objects of the same size, one is twice as far as the other from the viewpoint. The further one will always look half the size of the closer one, the closer will always look twice the size of the further (these two statements mean the same thing) no matter how much you zoom or crop or change sensors or pick which one is the subject.

Your question about composition doesn't really make sense if you think about it. Two photos that have the same composition, by definition, will look exactly the same in terms of perspective, angle of view, and where the camera is pointing. If you change any of this then they do not have the same composition. To get the same composition on APS-C and FF you take two lenses with equivalent angle of view (e.g. 50/APS-C and 75/FF), stand in the same spot and point them at the same thing. As a result, everything in the photos will look exactly the same (besides DOF).

PS: sorry for continuing to hijack this thread.

Last edited by Cannikin; 11-16-2012 at 11:30 PM.
11-18-2012, 06:35 PM   #27
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QuoteOriginally posted by Cannikin Quote
I think you're a bit confused here. Perspective has nothing to do with focal length, only camera position (ignoring distortion from rectilinear/gnomonic projection).

If two lens/sensor combos have equivalent angle of view (e.g. 55mm/APS-C and 82.5mm/FF), to get the same composition they would be shot from the same position, and thus the perspective will be identical.
I guess I didn't explain myself clearly enough.

What I was trying to say is that for the same framing/FOV, you would need to be further away with the 70mm (hence my comment regarding backing into walls), giving a different perspective.
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