Åmund Posted February 20, 2011 Share #1 Posted February 20, 2011 Advertisement (gone after registration) This may very well be a very stupid question, but so far this forum has treated my earlier stupid questions kindly so I risk it one more time. Even I know that you use a long lens when you want to draw a far off motive closer to you, a short lens when you want to get as much motive as possible inside the frame and a medium length lens for everything else. But, given a M9 with a lot of pixels, can´t you get the tele effect if you crop a picture taken with a short/medium length lens and then enlarge the crop? You will of course loose a lot of pixels, but if you don´t intend to print it out in A1 format, you will still get a fairly good resolution? Or is there any particular characteristics that follows each length that cannot be done with other lengths? I quote from the spec on the Apo-Telyt-M 135 mm f 3,4 ASPH: "It permits distinctive landscape shots with typical telephoto effects: the foreground and background are visually compressed". This didn´t make much sense to me and, truth to tell, I couldn´t spot it on the picture that accompanied the text either, so maybe some of you wizards out there could explain? Regards Åmund Link to post Share on other sites More sharing options...
Advertisement Posted February 20, 2011 Posted February 20, 2011 Hi Åmund, Take a look here Which lens to use when?. I'm sure you'll find what you were looking for!
spydrxx Posted February 20, 2011 Share #2 Posted February 20, 2011 On the cropping question, you introduce more "graininess or pixelness" as you enlarge the crop...so yes, a telephoto of longer length is usually a much better answer. The second one I'll leave to other for details, but yes, each lens has distinctive characteristics which might not be replicated by another lens of similar focal length. For instance my 400mm Telyt has a sharp central area of focus, increasing in softness toward the edges, also true of light transmission....making it a good lens for nature work where my subject is always centered in the photo. Link to post Share on other sites More sharing options...
earleygallery Posted February 20, 2011 Share #3 Posted February 20, 2011 Even I know that you use a long lens when you want to draw a far off motive closer to you, a short lens when you want to get as much motive as possible inside the frame and a medium length lens for everything else. But, given a M9 with a lot of pixels, can´t you get the tele effect if you crop a picture taken with a short/medium length lens and then enlarge the crop? You will of course loose a lot of pixels, but if you don´t intend to print it out in A1 format, you will still get a fairly good resolution? Whilst your description is factually correct, it's also fundamentally wrong! The focal length of a lens affects the perspective, and depth of field and many other factors in actual use. A wide angle lens will squeeze more image into the frame, but the point of using a wide is more to do with use of perspective, giving depth to an image, or getting close to your subject. A telephoto lens has the opposite effect on perspective, it can 'pull' the background and foreground together (the effect you mention). There are many books and no doubt websites which will explain this more fully and show example images. The limited depth of field of a telephoto lens also makes it easy to isolate the subject, be it detail in a scene, a portrait or wildlife/sport photography (look at the photos of football matches in the paper, notice how the background is out of focus). Which lens to use when? There are no rules about that, use what you have, or what you want. You can take sports and portraits with wideangle lenses, just as you can take landscapes with a telephoto. I'm sure you'll get lots of additional explanations but hope this helps. Edit: Look at this page http://www.luminous-landscape.com/essays/theartof.shtml - there's two images which demonstrate perspective, the yellow line on the road, showing use of a wide angle to get close up to the road marking and lead you into the distance of the image. Then the image of the trees/landscape next to it. Notice how the telephoto lens makes everything appear to be on the same plane? you can't really tell how far apart the trees and hills are. Link to post Share on other sites More sharing options...
wattsy Posted February 20, 2011 Share #4 Posted February 20, 2011 The focal length of a lens affects the perspective, and depth of field and many other factors in actual use. DOF is complicated by questions of CoC, etc. but perspective has nothing to do with focal length. Link to post Share on other sites More sharing options...
earleygallery Posted February 20, 2011 Share #5 Posted February 20, 2011 Ian, I'm trying to explain things to someone who appears to be a novice. Perhaps you could address the question and expand on your comments in a simplistic manner and contribute to the thread for the OP's benefit? Link to post Share on other sites More sharing options...
Jeff S Posted February 20, 2011 Share #6 Posted February 20, 2011 The OP may find some of the info here useful, including some 'mouse-overs'. Note issues relating to camera shake etc. when choosing focal lengths. And, as pointed out in the article, perspective is only affected by distance from camera to subject. So focal length has no bearing on perspective (one can crop for same effect), except if one chooses to adjust the camera position when choosing different focal lengths. Jeff Link to post Share on other sites More sharing options...
01af Posted February 20, 2011 Share #7 Posted February 20, 2011 Advertisement (gone after registration) The focal length of a lens affects the perspective ... That's a common misconception. As a matter of fact, changing the lens' focal length (and keeping everything else constant) will only change the field of view; the perspective won't get changed the slightest bit. However the crucial part of the statement above is the part in the parentheses. "Keeping everything else constant" is exactly what you usually won't do. Instead, with a wide-angle lens you will step closer to your subject; with a telephoto lens you will shoot the same subject from farther away. And that is what affects perspective—the various distances you're shooting from. The simple fact that short distances typically are connected to wide-angle lenses and long distances to telephoto lenses leads to the misconception it were the focal lengths which affected perspective. But in fact, it's the distances. Unless you're a sports or wildlife photographer who simply cannot freely approach his subjects as he might want to, you mustn't just choose your lens according to the distance the subject happens to be at in the moment you spot it. Instead, you thoughtfully and deliberately choose the distance that you want to shoot your subject from. Step closer and step back, see from which distance the various parts of your image (foreground and background in particular) come together in the most favourable way, and then pick the proper focal length accordingly. That's what a palette of different focal length lenses is for. Cropping the central part from a photograph will indeed yield the same result, geometrically, as shooting with a longer focal length. But the loss of pixels will lead to a lower image quality overall so this is not considered good practice generally. Think of cropping as a belated action to fix a shot after the fact when the proper (longer) focal length wasn't available at the time of shooting. After all, often a less-than-perfect shot is better than no image at all. Link to post Share on other sites More sharing options...
masjah Posted February 20, 2011 Share #8 Posted February 20, 2011 DOF is complicated by questions of CoC, etc. but perspective has nothing to do with focal length. It does indirectly, because changing focal length facilitates moving towards or away from your subject and background, whilst still having a similar image size.. OK I'll chip in and try to explain a little to the OP. Suppose you are 100m away from your subject, using a long lens, with something else 10m behind it. Then the two elements won't appear that much separated in depth, because the separation represents only 10% of the subject distance. Now move close to your subject so that you are only 10m away fom it, using a wide angle lens, so that the subject is the same sort of image size. Then the two elements will appear much more separated in depth, because the separation distance now represents 100% of the subject distance. In other words the perspective has changed. I suggest you try out this experiment for yourself, walking in and out, using different focal length lenses - you'll soon get a feel for it. Hope this is all not too self evident for you - apologies if it is. Link to post Share on other sites More sharing options...
earleygallery Posted February 20, 2011 Share #9 Posted February 20, 2011 OK I perhaps didn't explain fully enough, O1af has put it succinctly. It's also a misconception that depth of field changes but if we start getting into the details of circles of confusion we're going to completely baffle the OP! Re. cropping an image, there are many on this forum who will tell you that you should never crop an image, because HCB never did it (although he did of course). Minor cropping, to remove a distraction in the background or to fit an image to a particular format (what if you want a square image, but don't use as Hasselblad?) is perfectly fine. But cropping to emulate a telephoto lens - whilst you may need to do it on occassion, isn't to be recommended if image quality is important to you. If you only have one lens then use your feet wherever possible! Link to post Share on other sites More sharing options...
01af Posted February 20, 2011 Share #10 Posted February 20, 2011 It's also a misconception that depth of field changes ... Umm—actually, depth of field does change (becomes deeper in the cropped image). Whenever you change something, DOF will also change ... always. You simply cannot take the same picture with two different-format cameras (or as two shots with one camera but crop one of the shots which effectively means the same) and end up with two images that are exactly the same in every aspect. Impossible. When the size and position of DOF are the same then plane of focus and background blur will be different. When the plane of focus is the same then either position or size of DOF will be different. And so on and on and on. When they say, "for the same DOF on a smaller-format camera you need a wider aperture" then that's approximations only. In real life, that's more than close enough, but when you're scrupulous then you simply cannot get exactly the same DOF. We really don't need to go any deeper into this here and now ... but be reassured the topic will get awfully complex when you try to dive into the finer details. Link to post Share on other sites More sharing options...
giordano Posted February 20, 2011 Share #11 Posted February 20, 2011 A demonstration (a) that focal length doesn't affect perspective and ( that cropping affects quality: Link to post Share on other sites More sharing options...
earleygallery Posted February 20, 2011 Share #12 Posted February 20, 2011 As I said in my original response the lens in actual use then perspective and dof do affect lens choice, I think the shots I linked to demonstrate what I was trying to say better than my brief words. I was being overly simplistic for the benefit of the OP but hey ho. Anyway I'm off now, to explain Dadaism to a two year old. Link to post Share on other sites More sharing options...
Xmas Posted February 20, 2011 Share #13 Posted February 20, 2011 Hi What you need to do is borrow a SLR or DSLR with a zoom lens and look through the finder. You have described the zoom technique that you can do with simple digital cameras, or with an enlarger and wet print, i.e. to magnify the centre of the image at the expense of quality. Noel Link to post Share on other sites More sharing options...
ho_co Posted February 21, 2011 Share #14 Posted February 21, 2011 Åmund, while everyone is now off whipping his own dead horse, I'll try not to respond to your question as well: 1) Best way to learn which lens to use when is to carry your camera with only one lens for a day or a week or longer. Make the best pictures you can with that lens in terms of composition. And notice whether you're happy with that lens, or whether you'd like a tighter crop, or whether you'd like to take in more of the image and use the wider view to add a dimensionality you wouldn't have otherwise. To do this, the frame preview lever can be a great help: What would I get if I were using a 90, or a 28, etc? 2) Rule-of-thumb: When you see something that catches your eye, shoot it immediately before you go explore it. That's because the shapes/volumes that caught your eye will only look that way from exactly where you are. Moving a meter to the left will often change the view, as will walking five meters forward. It may be that you'll get a better picture by moving backward and to the right, but that's what you'll discover when you start exploring the subject. The lighting may change, or people may walk into or out of the image space, and completely change what you see, so capture it immediately. There's no way to answer the question you asked. Some photographers work only with a single lens. (See Liz Loh-Taylor's portfolio in LFI 2/2011, all made with M9 and 35/2 Asph.) Others may have two or three or ten. But you'll do your best by learning to work with the lens that's on the camera. You make the picture, and you make the picture count. You won't take the same picture with a 21mm as you would with a 90mm. You learn to see what the lens sees and that will tell you whether you need another focal length. You asked if you couldn't just enlarge the center out of a wide-angle image to get the same shot as with a telephoto. Broadly speaking, all the optical rules seem to say so, but that's your last resort, never your first. There are two reasons: 1) Blowing up a small image more just enlarges its defects. (See the left side of John's picture above.) The pixels and unsharpness that you don't see when you look at the whole image are blown up and can become distracting. 2) Due to the constraints of optical design, wide-angles are designed differently from telephotos. That is, if you want the fly on the horse's neck, use a longer lens; in general, wide angles don't have the same contrast or resolution as their longer cousins. (I'll stick by the general statement, though it can be picked apart by people who want to show you how smart they are. ) That, in summary, is what everyone else in the thread is saying, except Noel. I differ with his suggestion and think it's counterproductive, but I'm only speaking for me. The advantage of the rangefinder is the limited range of focal lengths available; it forces you to think. An SLR is far easier, because you can put an 18-200 zoom on and take hundreds of bad pictures without moving an inch from where you are. Link to post Share on other sites More sharing options...
holmes Posted February 21, 2011 Share #15 Posted February 21, 2011 First you need to do some homework. Get a good book that describes what the various focal lengths will cover. Then take your lenses and find a non-complicated landscape. Change your lenses and observe what each brings into, or leaves out of the viewfinder. You can also use the switch on the left front of your "M" and it will bring up whatever lenses are engraved. Next you have to decide what it is you want to convey with your photo. The "Photographers Handbook" by British author/photographer John Hedgcoe. He goes into detail of what your lens can do. Has excellent illustrations (photos) showing the difference. When you ask the question, "what lens should I use"? That tells me you are a very inexperienced photographer. We all were at one time or another. Then experiment, experiment until you know what every lens inn your bag can do and will it give you what you are looking at. Link to post Share on other sites More sharing options...
Jeff S Posted February 21, 2011 Share #16 Posted February 21, 2011 O1af has put it succinctly. Perhaps my second paragraph was too succinct. Jeff Link to post Share on other sites More sharing options...
Åmund Posted February 21, 2011 Author Share #17 Posted February 21, 2011 Well, as the novice said (and I am indeed one): "I´m still confused, but on a higher level" Thank you all for your engagement and good advice. As soon as the weather improves (it is freezing cold here, and although the M9 can stand it, I´m not very keen on sub zero temperatures) I shall hoist up my gear, get out and shoot! Regards Åmund:D Link to post Share on other sites More sharing options...
adan Posted February 21, 2011 Share #18 Posted February 21, 2011 The "perspective" of a picture depends soley on the location of the lens - the "point of view." If a photographer CHOOSES to change location (i.e point of view) because s/he is using a particular lens - that is something that takes place between the photographer's ears. It has nothing to do with the optics. "My lens made me do it" is not an acceptable shifting of blame (or credit). Given an infinitely-resolving imaging material (which is fantasy for either digital or film) - one could in fact use one wide-angle lens of sufficient speed and quality (also a fantasy) to produce any picture, simply by cropping. The one exception being fish-eye rendering vs. rectilinear rendering for superwides. So, yes, you can easily get the "tele" effect by cropping. However, you will run into the problem that the real world does not conform to the fantasies I mentioned above (as John demonstrates in post 11) - so you'll noticeably lose image quality at anything much over a 2x crop. (A 2x crop cuts the pixels by 4x, thereby turning an M9 into a 4.5 Megapixel camera. A crop from 50mm to 135mm (2.7x) results in a 1 megapixel image.) The attached picture works the other way around - a fisheye superwide view of the world produced with a 50mm lens on an M8 ("70mm" equivalent FoV). Via stitching 20-odd frames together. Except for the disconnects caused by people motion, and the (intentional) irregular border, there is no way to distinguish it from a single picture made with one ~20mm fisheye lens. Not DoF, not "perspective," nada. Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/144562-which-lens-to-use-when/?do=findComment&comment=1594737'>More sharing options...
SJP Posted February 21, 2011 Share #19 Posted February 21, 2011 Maybe this will help (note camera to stuffed shark distance is the same in all images, also all shots are at f/2.8, taken with M8) 28 mm full frame 28 cron | Flickr - Photo Sharing! 90 mm full frame 90 tele-elmarit | Flickr - Photo Sharing! same as no. 1 (28 mm) but cropped to the same frame size as 90 mm 28 cron-crop | Flickr - Photo Sharing! The perspective is the same for all three images as the camera to object distance did not change. Also note that the cropped 28mm shot (no 3) has a greater depth of field despite being taken at the same aperture of f/2.8. Link to post Share on other sites More sharing options...
jaapv Posted February 21, 2011 Share #20 Posted February 21, 2011 The "perspective" of a picture depends soley on the location of the lens - the "point of view." If a photographer CHOOSES to change location (i.e point of view) because s/he is using a particular lens - that is something that takes place between the photographer's ears. It has nothing to do with the optics. "My lens made me do it" is not an acceptable shifting of blame (or credit). Given an infinitely-resolving imaging material (which is fantasy for either digital or film) - one could in fact use one wide-angle lens of sufficient speed and quality (also a fantasy) to produce any picture, simply by cropping. The one exception being fish-eye rendering vs. rectilinear rendering for superwides. So, yes, you can easily get the "tele" effect by cropping. However, you will run into the problem that the real world does not conform to the fantasies I mentioned above (as John demonstrates in post 11) - so you'll noticeably lose image quality at anything much over a 2x crop. (A 2x crop cuts the pixels by 4x, thereby turning an M9 into a 4.5 Megapixel camera. A crop from 50mm to 135mm (2.7x) results in a 1 megapixel image.) The attached picture works the other way around - a fisheye superwide view of the world produced with a 50mm lens on an M8 ("70mm" equivalent FoV). Via stitching 20-odd frames together. Except for the disconnects caused by people motion, and the (intentional) irregular border, there is no way to distinguish it from a single picture made with one ~20mm fisheye lens. Not DoF, not "perspective," nada. Errr... This is a rectilinear perspective - a fisheye has a centric perspective. It looks in no way like a fisheye shot. It looks like a shot with an extremely well-corrected 21 mm lens. The only way to avoid the fisheye look with a fisheye lens is to avoid recognisable straight lines and perspectivic elements towards the corners. I've published this fisheye shot before: Welcome, dear visitor! As registered member you'd see an image here… Simply register for free here – We are always happy to welcome new members! Link to post Share on other sites Simply register for free here – We are always happy to welcome new members! ' data-webShareUrl='https://www.l-camera-forum.com/topic/144562-which-lens-to-use-when/?do=findComment&comment=1594813'>More sharing options...
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