Help with lenses please.

[madlights]

Yeah.. my mistake for using the phrase. I forget and should add more about such things instead of being lazy and making general comments. Here's an article with comparison shots which is good to pass out instead. I think it should clear things up pretty well.
http://www.photonomics.com/chooselensa.htm

Thanks dang for the great link...sure does clear up the difference between the perceived and the technically correct...great link.

[madlights]

While it is true that the only thing that changes perspective is the position of the lens to the subject. Different lenses do cause foreshortening...it isn't because a dog is closer to a wide angle that his nose looks longer, but rather because precisely that the perspective is the same. A wide angle lens exposes us to more acute lines of perspective, since the field of view is wider. A telephoto narrows the field of view so only the less acute angles of perspective are seen. Because of the acute angles in a wide angle, subjects close to us placed upon a plane of perspective appear farther apart along that plane....and a telephoto foreshortens by only "showing" us a narrower view, where the subjects are placed on a much less acute angle. However as dick correctly points out the perspective does not change...but because of the relative differences in lens properties at different focal lengths it is very difficult to determine just what variance a FF lens on a 1.5 or 1.6 crop factor would have. Since the only place lenses are equal at a given mm is at infinity focus...as dang has so aptly pointed out in another thread. This is a good thread...and has actually caused me to think. Whooaaa!

[thayer16]

Hey guys....I've been browsing the great photos on this site for a few months now, but reading this thread caused me to join, as I've been wondering the same things discussed here. I have a Canon Rebel 35mm with a Sigma 24mm - 70mm f.3.5 - 5.6 (or something, if you can explain what these numbers mean too that'd be great). I've been considering a Canon DSLR since I can use the lenses I have now. I like the wide angle of the 24mm, but from what I hear here , on a DSLR this will be like a 38mm. From what you guys say, I'll have to stand farther away from the subject and am afraid I wont be able to get the same look of a wide angle perspective. If I want the same look from my DSLR as with film, I'd need to get a 15mm lense, right? This will allow me to get closer to my subject and get "more acute lines of perspective" so backgrounds appear farther back? Do I have this right? If this is so, than my reasoning for sticking with Canon (so I can keep my wide-ish angle lense) is moot, since I'll have to buy a new lense anyway. My brain hurts - I liked it better when I could just take a picture, wait a week for it to get developed, and not worry about the science behind it all. Thanks for your thoughts......

[madlights]

Hi thayer
Yep, right on the angle of view if you have any Canon DSLR below the 5d...say the 20-30d or the Digital Rebel series. Those cameras crop the picture by a factor of 1.6, The 5d is a full frame or the same as 35mm for all practical purposes as is the 1ds series. To confuse things the 1d series - not to be confused with the 1ds...is a 1.3 crop. So that's right your wide angle lenses aren't so wide angle anymore. It's due to the fact that these cropped factor cameras have smaller sensors than 35mm...since I guess it costs a great deal more to manufacture the 35mm equivalent size sensors. So what "in effect" these cropped factor cameras do is "see" a smaller circle of the light coming in the camera. I think after a bit you'll like the fact that once you get all set up and accustomed to digital that the instant "developing" is pretty cool (and free). The one disadvantage I've found because of this. is that I tend to use my digital camera more like a machine gun now...instead of really thinking out my shots as I did with film. Good luck and have fun.

[dang]

Hi Thayer, and welcome to Pbase.

Don't forget though, this also has an advantage since it' increases the reach of your longer lenses. So, for instance, it allows better magnification if shooting birds without having to get as close. You might only need to get another wide angle instead of buying all new lenses if you've already invested in glass. Also, since Canon has one of the best sensors available, it's a good choice to go with.

There's several reasonably priced ultra wide zooms available now in the 10-20, or 12-24mm range which will allow an even wider view than your current 24mm on full frame. Just be aware when purchasing, some lenses are digital specific and won't work with full frame if you upgrade in a few years. For Canon lenses, EF works on both while EF-S are digital specific. But they are both subject to the crop factor of the body.

Good luck, and happy shooting regardless of which system you get.

[sean_mcr]

While it is true that the only thing that changes perspective is the position of the lens to the subject. Different lenses do cause foreshortening...it isn't because a dog is closer to a wide angle that his nose looks longer, but rather because precisely that the perspective is the same. A wide angle lens exposes us to more acute lines of perspective, since the field of view is wider. A telephoto narrows the field of view so only the less acute angles of perspective are seen. Because of the acute angles in a wide angle, subjects close to us placed upon a plane of perspective appear farther apart along that plane....and a telephoto foreshortens by only "showing" us a narrower view, where the subjects are placed on a much less acute angle. However as dick correctly points out the perspective does not change...but because of the relative differences in lens properties at different focal lengths it is very difficult to determine just what variance a FF lens on a 1.5 or 1.6 crop factor would have. Since the only place lenses are equal at a given mm is at infinity focus...as dang has so aptly pointed out in another thread. This is a good thread...and has actually caused me to think. Whooaaa!

That's actually incorrect my friend. Perspective distortion has nothing to do with the lens. It's the distance to subject and the distance from which the shot is viewed.

http://en.wikipedia.org/wiki/Perspectiv ... ography%29


Simple test, hold your five fingers out in front of your face, claw like and move them closer and further from your eyes. That's perspective distortion in action and it's not your eyes fault any more then it's a len's when it happens. It's your distant to subject

It's not the narrow view of a tele that gives for a more flattering portrait it's the distance from the subject. That's why the traditional focal lengths for a standard portrait is 85-135mm and not 35mm to 50mm. It's not the narrow angle of view its the distance that the focal length allows us to lessen the effect of perspective distoriaon.

Two shots with no cropping involved other then my distance to subject

35mm prime (on a 20D)


Obvious signs of perspective distortion


135mm (also on a 20D)



The framing of the two shots are simalar. I forgot to resize the the 135 shot to that of the 35 but the differnce is obvious and it's not the lens. It's simply that to frame in the same way as in the 135 shot, i have to get too close to my subject. I shoot with 35 90% of the time i know it inside out.

Dog nose or human nose, it's not the lens. It's the distance to subject

I'm not trying to be clever or anything like that my friend. You're just mistaken


Shot with the 35 but this time from further away



Where's the distortion gone and why's it gone? It's simply the distance to subject

Take care

Keep shooting

Sean

[dang]

Sean wrote:

That's actually incorrect my friend. Perspective distortion has nothing to do with the lens. It's the distance to subject and the distance from which the shot is viewed.

Actually, it's not all that simple. I've tried to get the point across that "Perceived Perspective" does vary from one lens to another, but had a difficult time finding the proper way to express it since it's been years since I learned about it myself. However, we had a discussion about just this in the other thread, which explains why different size lenses do play a factor, even though perspective does not change... it's definitely influenced by lens properties closer in. And it's done with test photos which you'll find the link to. Lenses angle of view is only rated for infinity, a point which is often overlooked. So making a blanket statement that only distance is a factor, doesn't take this into account. Different millimeter lenses (due to their characteristics) may require different focusing distance to achieve the same subject size in the frame when focused closer in.
http://forum.pbase.com/viewtopic.php?t=30349

[sean_mcr]

Sean wrote:

That's actually incorrect my friend. Perspective distortion has nothing to do with the lens. It's the distance to subject and the distance from which the shot is viewed.

Actually, it's not all that simple. I've tried to get the point across that "Perceived Perspective" does vary from one lens to another, but had a difficult time finding the proper way to express it since it's been years since I learned about it myself. However, we had a discussion about just this in the other thread, which explains why different size lenses do play a factor, even though perspective does not change... it's definitely influenced by lens properties closer in. And it's done with test photos which you'll find the link to. Lenses angle of view is only rated for infinity, a point which is often overlooked. So making a blanket statement that only distance is a factor, doesn't take this into account. Different millimeter lenses (due to their characteristics) may require different focusing distance to achieve the same subject size in the frame when focused closer in.
http://forum.pbase.com/viewtopic.php?t=30349

Yes Dang but thats not the fault of the lens that's simply trying to use two different lenses in the same way. You can not take a head and shoulder portrait with at 35mm with out some distortion. That's because it was not intended to be used for that subject matter as it will not flatter the subject due to perspective distortion

The link i gave could not have made my point clearer. I recall the conovo we had wehn we first met and actaully i owe you some plugins

I've got to disagree with you pal

Edit.

The first two shots show that you have to be much closer with the 35mm to frame the shot in the same as the 135. But you're not meant to frame in the same way with those two lenses. The 135 was designed to to have a longer focusing distance in order take a portrait with out subject to distance distortion (or at least greatly reduce the effect)


It's no different to how our eyes see. Go and have a close look at your face in the mirror, closer you get the more distorted your face will appear. but that's nothing to do with your eyes that's simply distance to subject distortion before your very eyes

[dang]

Laffin'..
I think we're saying the same thing, but in different ways. No One has argued the fact that perspective is due to distance. And, you only clarified the point which was being made. That lenses ARE made to do different jobs, and are not always interchangeable because of this. That they do distort differently, and the point was just this! So, when used with a crop factor these characteristics still play part in the outcome, regardless of perspective.

[sean_mcr]

Laffin'..
I think we're saying the same thing, but in different ways. No One has argued the fact that perspective is due to distance. And, you only clarified the point which was being made. That lenses ARE made to do different jobs, and are not always interchangeable because of this. That they do distort differently, and the point was just this! So, when used with a crop factor these characteristics still play part in the outcome, regardless of perspective.

Lol

But again it's not the lenses that do it it the distance. If you use them right it not an issue


Plugins coming your way;)

[thayer16]

Lets say you take the same shot, say a portrait, with a 24mm & 100mm lens from the exact same distance from the subject. The one taken with the 24mm will appear smaller (correct me if I'm wrong at any point). If you blow up and crop this image so it fills as much of the frame as the 100mm image, will the two look the same? If distance from lens to subject is the only contributing factor to perspective distortion than they should look the same. At least that's what I'm getting from this discussion. Am I wrong.???

[madlights]

I gotta think about this some more. Edit: OK I thought some. If you represent perspective by drawing an X on a piece of paper and putting objects equally distant along those lines. Say telephone poles on a road...the farther away they get, the closer they are together. If you took a photo of the center of this imaginary scene with a telephoto lens, the objects are still close together (foreshortening) If you took a photo with a WA the objects would appear farther apart? If you narrow the field of view, which a telephoto does, would not distant objects 'appear' closer in relation to each other? This is a good thread...if I am wrong I will learn something. If I am right I will learn something since I've had to think...and if we are saying the same thing in different ways...I've learned to communicate

[dang]

Thayer wrote:

Lets say you take the same shot, say a portrait, with a 24mm & 100mm lens from the exact same distance from the subject. The one taken with the 24mm will appear smaller (correct me if I'm wrong at any point). If you blow up and crop this image so it fills as much of the frame as the 100mm image, will the two look the same?

Basically yes. But we don't want to crop that much since we cut down file size, increasing noise/grain and lose detail.

Since You can't fill the frame with the subject equally, at the same distance to subject, with two lenses that have different magnifications. And that IS the point I was making. And that people can't always use one lens to do the job of another, because it forces them to change distance, and thus change perspective. Also, a lenses angle of view is rated at infinity only. Once they're focused closer, their angle of view can vary.

Another way... If you leave a camera at the same place after taking a shot with a lens which has greater magnification than the one you are now using, you can not get the same magnification without cropping. And, if you don't crop, you have a different perceived perspective, simply because you'll have more background in the image, and a smaller primary subject. Here again, It's the difference between magnification which causes people to change camera to subject distance, thus changing perspective. And this is the lens characteristic I'm speaking about.
Sean wrote:

But again it's not the lenses that do it it the distance. If you use them right it not an issue

What have I been saying? But if you don't have the right lens, what do you do? You wind up with a shot of less than desirable look.
Earlier I wrote:

Different millimeter lenses (due to their characteristics) may require different focusing distance to achieve the same subject size in the frame when focused closer in.
http://forum.pbase.com/viewtopic.php?t=30349

How many ways must I say it?
I don't understand why you keep repeating that I'm wrong, only to say something I've already pointed out!

Dpreview Syndrome...
or my Southern accent?

[madlights]

I think we're all saying the same thing in different ways. A lens doesn't change perspective...OR foreshortening. Distance changes foreshortening. A Wide angle lens shows a wider field of view. A tele a narrower. You see MORE of what's close with a wide angle. This is all compared to the same camera to subject distance. If you cropped the WA at a high enough resolution you would see EXACTLY the same thing as you would in the tele....but distance DOES foreshorten...the telephone poles on a road get closer together as distance increases. We would have to stand closer or farther from our subject with different lenses to get the same FOV with different lenses, which would change the perspective and the foreshortening. Different lenses...Tilt shift fisheyes etc. can change perspective. Cropped cameras do nothing but crop an image. I think we all are just talking different color apples here, rather than apples and oranges.

[thayer16]

It does seem to me that we're all saying the same thing, but in slightly different terms. Ultimately, I think we agree that the distance from lens to subject is by far the greatest contributer to perspective in a final image, while using the appropriate focal length lens can contribute to the final image quality. Either way, as Madlights said, I'm learning because I'm thinking about something in a way I never have before. And as a great American once said "Knowing is half the battle". I'm starting to enjoy the forum section of this site as much as the galleries. Thanks for sharing all your collective knowledge.

Edit: Madlights, I think we were typing at the exact same time. Great minds must really think alike