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Thread: Lenses

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    Lenses

    Hi, Im new to all this photography terminology and what lenses to use. I love taking photos but am struggling with what to use when. If I am taking a photo of single objects, eg. tissue box or an ornament... would it be suitable to use a 90mm? If I get too close with my 55mm its looks warped and I want the background blurred? Thanks.

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    Re: Lenses

    I assume you have a crop sensor camera and a 90mm would be considered to be a mild telephoto on it but it is a very useful focal length for either full frame or cropped formats. At wide apertures it will assist in reducing depth of field thereby blurring the background. For maximum blur make sure the background is as far away from the item of interest as practical.
    Enjoy experimenting.

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    Re: Lenses

    Quote Originally Posted by Alisa View Post
    Hi, Im new to all this photography terminology and what lenses to use. I love taking photos but am struggling with what to use when. If I am taking a photo of single objects, eg. tissue box or an ornament... would it be suitable to use a 90mm? If I get too close with my 55mm its looks warped and I want the background blurred? Thanks.
    Welcome to the forum, Alisa,

    Good advice above. You are experiencing one of photography's many conflicting requirements!

    Do you have one of the more complicated image Editors, such PhotoShop or Photoshop Elements? They usually have a means of reducing image distortion caused by the dreaded "perspective" and other types of distortion more to do with the lens, e.g. barrel distortion.

    If you use a 90mm to reduce the effect of perspective, the relative distance of the background from the lens versus the distance of the subject will work against you because the apparent "depth of field" will be more than if you were to shoot closer to the subject.

    My inclination would be to use the 55mm and use perspective correction - should the subject's appearance be objectionable. I didn't bother to do that with this eBay shot but a tissue box or tall "leaning" buildings would benefit.

    Lenses

    Items are about 5" tall, shot from 18" or so.

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    Re: Lenses

    Quote Originally Posted by Alisa View Post
    Hi, Im new to all this photography terminology and what lenses to use. I love taking photos but am struggling with what to use when. If I am taking a photo of single objects, eg. tissue box or an ornament... would it be suitable to use a 90mm? If I get too close with my 55mm its looks warped and I want the background blurred? Thanks.
    Welcome to the forum, Alisa,

    Good advice above. You are experiencing one of photography's many conflicting requirements!

    Do you have one of the more complicated image Editors, such as PhotoShop or Photoshop Elements? They usually have a means of reducing image distortion caused by the dreaded "perspective" and other types of distortion more to do with the lens, e.g. barrel distortion.

    If you use a 90mm to reduce the effect of perspective, the relative distance of the background from the lens versus the distance of the subject will work against you because the apparent "depth of field" will be more than if you were to shoot closer to the subject. Therefore, a blurred background becomes more difficult. If you are doing table-top (product) photography, it may be better to change the background as in below where a simple cloth does the trick. Then you can go for more depth of field with a bigger aperture number.

    My inclination would be to use the 55mm and use perspective correction - should the subject's appearance be objectionable. I didn't bother to do that with this eBay shot but a tissue box or tall "leaning" buildings would likely benefit.

    Lenses

    Items are about 5" tall, shot from 18" or so.
    Last edited by xpatUSA; 28th June 2013 at 04:37 PM.

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    Re: Lenses

    Quote Originally Posted by xpatUSA View Post
    !

    If you use a 90mm to reduce the effect of perspective, the relative distance of the background from the lens versus the distance of the subject will work against you because the apparent "depth of field" will be more than if you were to shoot closer to the subject. .
    Surely Ted you must know that for a given image size the depth of field is the same irrespective of what focal length lens you use, only the perspective changes?

    I normally use a longer focal length for closer subjects but that is becuase I probably am using a different range of options. If you are lighting a smallish subject it helps to stay back from the subject.

    EDIT ... if you want a blurred background it is easy enough to do this in editing by duplicating the image, blurring the top layer and then erasing the portion of the top layer you want to be sharp, revealing the sharp image in the bottom layer. If it has fine detailed edges it may be preferable to use a layer mask but usualy a soft erase brush works well and avoids the 'cut-out' look. IMO rarely is the b/g sufficiently out of focus in-camera so I do not bother, knowing I can do it in editing. But you do need to have practiced as much with your editor as with your camera to adopt such an approach.

    E2 .... if your editor doesn't have the layers ability there is a free download which does a reasonable job Paint.Net.
    Last edited by jcuknz; 28th June 2013 at 10:00 PM.

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    Re: Lenses

    Quote Originally Posted by Alisa View Post
    Hi, Im new to all this photography terminology and what lenses to use. I love taking photos but am struggling with what to use when.
    There are no hard-and-fast rules for this. Everybody's different, and it also depends on the specific lens/camera combination you're talking about. Typically, you use a longer lens for subjects where your working distance is larger, and you use wider lenses for subjects where your working distance is smaller.

    If your working distance is very small, then macro lenses come into play.

    If I am taking a photo of single objects, eg. tissue box or an ornament... would it be suitable to use a 90mm? If I get too close with my 55mm its looks warped and I want the background blurred? ...
    The closer you get to an object while shooting it, the more the background will blur. The longer the lens you use, the more the background will blur. And the wider an aperture setting (smaller the f-number) you use, the more the background will blur. Just me, but in this case, a 55 vs. a 90 may not make that much difference, but the 55 (assuming the 90 we're talking about isn't a macro lens) can probably get closer to what you're shooting than the 90 can.

    If, however, the 90mm lens we're talking about is, say, a Tamron 90mm Macro lens, that's probably a better choice than an 18-55 kit lens for getting closeups of objects @18mm, particularly because of the distortion (warping) using a wide angle lens can create. If you were zoomed to 55mm on the 18-55, chances are you wouldn't see as much warping, but you'd probably have to be a bit farther back from the subject.

    So, what camera and lenses are we talking about here?

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    Re: Lenses

    Sorry Kathy Li ...but I came on a bit strong and have deleted it.

    The short lens only puts the background out of focus by the very nature that you are very close there is absolutely no difference in DoF. Greater minds than me established that before me Kodak for one, though when I read Kodak it just confirmed what I had worked it out for myself

    I think the use of the shorter lens comes from the usual practice, until recent 'two lens kits' came on the market, was for people to start with just a normal lens or a short zoom of recent years. Certainly the longest lens most people had was a 135mm and I only had a normal lens on the various cameras I owned and used until quite shortly before digital arrived for me. The smallness of the bridge camera lens made it feasible/ecconomical to add a close-up lens and introduced me to using a long focal length to get tight framing from further back. Which I had been doing previously with movies without being aware of what I was doing.

    There is also the widely held belief that the viewer prefers images taken with a normal lens and says we see with a normal lens ...I don't think I am particularly special be I certainly don't and suggest it is nothing to do with the focal length but rather the perspective that the normal lens gives which appeals ... that maybe a chicken and the egg situation of course

    I think it is good that Alisa has the choice and is making it on perspective grounds rather than a reluctance to ZWHLs.
    Last edited by jcuknz; 29th June 2013 at 02:19 AM.

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    Re: Lenses

    Wow, Thanks everyone for your responses! Definitely need to keep reading and learning to get my head around all of this!!

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    Re: Lenses

    Quote Originally Posted by jcuknz View Post
    Surely Ted you must know that for a given image size the depth of field is the same irrespective of what focal length lens you use, only the perspective changes?
    Yes, I've read that somewhere. However, my most serious pictures are of watches and eBay stuff for the Wife. So, if I shoot a watch to fill the frame with, say, a 50mm lens I might get a DOF of 5mm. And if I shoot that same watch to fill the frame with a 500mm lens then the DOF at the watch will still be 5mm, have I got that right? Pardon my confusion, I do tend to think in terms of angle rather than distance for many photographic parameters.

    EDIT ... if you want a blurred background it is easy enough to do this in editing by duplicating the image, blurring the top layer and then erasing the portion of the top layer you want to be sharp, revealing the sharp image in the bottom layer. If it has fine detailed edges it may be preferable to use a layer mask but usualy a soft erase brush works well and avoids the 'cut-out' look. IMO rarely is the b/g sufficiently out of focus in-camera so I do not bother, knowing I can do it in editing. But you do need to have practiced as much with your editor as with your camera to adopt such an approach.

    E2 .... if your editor doesn't have the layers ability there is a free download which does a reasonable job Paint.Net.
    Thanks for the advice but I don't use layers for anything, other than adding text in PSE.
    Last edited by xpatUSA; 29th June 2013 at 05:44 PM.

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    Re: Lenses

    Quote Originally Posted by jcuknz View Post
    The short lens only puts the background out of focus by the very nature that you are very close there is absolutely no difference in DoF. ...
    (sigh). I know. I know. But.

    http://theonlinephotographer.typepad...he-sequel.html

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    Re: Lenses

    I think that the fellow who wrote the article needs to calm down a little. The key is that he mentioned approaching the hyper-focal distance.

    Surely Ted you must know that for a given image size the depth of field is the same irrespective of what focal length lens you use, only the perspective changes?
    This statement should have included "as long as neither lens is close to or beyond its hyper-focal distance". It would then have been correct.

    I think we confuse others when we try to oversimplify things. Examples are: "telephoto lenses throw background out of focus because of REDUCED DEPTH OF FIELD", "200mm macro lenses are harder to hold because of REDUCED DEPTH OF FIELD", "light from all our photographic lighting equipment falls off at the same rate per the inverse square law" and on and on.

    OK, I will be quiet now.

    John

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    Re: Lenses

    Quote Originally Posted by PhotomanJohn View Post
    I think that the fellow who wrote the article needs to calm down a little. ...
    I've met ctein. He's constitutionally incapable of being less than fully enthusiastic about matters photographic.

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    Re: Lenses

    Sometimes a little knowledge can be dangerous......

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    Humble Pie Day today

    Surely, Ted, you must know that for a given image size the depth of field is the same irrespective of what focal length lens you use, only the perspective changes?
    "Humph!" I said to myself and rushed off to the workbench with the Panasonic and couple of lenses, having first fired off a smart-assed response to the above comment.

    Below, see living proof of how wrong I was . . .

    Lenses

    14mm, 45mm and 103mm - DOF same for each and background most blurred with the 103mm.

    Even worse is the memory of a tutorial over on LL on the same subject - duly read long ago and completely forgotten until I re-visited today, duh . .
    Last edited by xpatUSA; 30th June 2013 at 07:08 AM.

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    Re: Lenses

    Quote Originally Posted by Alisa View Post
    Wow, Thanks everyone for your responses! Definitely need to keep reading and learning to get my head around all of this!!
    That's good.

    But what would also be useful for you, is if you answered Kathy Li's questions:

    Quote Originally Posted by inkista View Post
    There are no hard-and-fast rules for this. . .
    So, what camera and lenses are we talking about here?
    WW

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    Re: Lenses

    #14 Since there is a marked difference in the size of the ornament beside the ruler, which is different also, I cannot see how you are following what I said... for a given image size DoF remains the same irrespective of what focal length lens you are using.

    I am not sure what we are arguing about becuase it is a fact of life beyond discussion.

    Probably the correct answer for Alisa is you use the lens that gives you the perspective of the subject you want, so people who like hideously distorted faces use an extreme wide angle lens while others use a longer lens.

    As for tissue boxes if we didn't live in a silly 'advanced?' age where one camera type is expected to do everything for a tissue box we would be using a large format bellows camera with full movements. A camera type I suspect that has fallen victim to the digital age. But Alisa please ignore this para as it is an esoterical comment to enrage some Such cameras often have one lens which do everything but have the ability to overcome the problems encountered, such as distorted tissue boxes
    This was my Thornton Pickard clone which only had limited movements before I sold it a year or two ago. You can see the 5x4 back I added and the Kodak lens which replaced the original Rapid Rectilinear.
    Lenses
    The RR lens did have an interesting ability, normally a 8" lens but by removing half of it it became a 15" lens.
    Lenses

    #15 WW ... My guess is a full frame film camera with normal and short portrait lens?
    Perhaps a Pentax with the 55mm lens?
    lets have a guessing game and then Alisa will tell us who is correct
    Last edited by jcuknz; 1st July 2013 at 02:25 AM.

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    Re: Lenses

    Quote Originally Posted by xpatUSA View Post

    Thanks for the advice but I don't use layers for anything, other than adding text in PSE.
    LOL . really I think you are hopping along on one leg, you should try layers and see how brilliant an idea they are by whoever came up with the concept. Ordinary layers and layer masks ... truely wonderful tools for us to use I use layers in connection with almost every shot I take into editing ... "life would end if I didn't have it, it didn't start until I finally worked out how to use it"
    Last edited by jcuknz; 1st July 2013 at 02:26 AM.

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    Re: Lenses

    Surely, Ted, you must know that for a given image size the depth of field is the same irrespective of what focal length lens you use, only the perspective changes

    There is an important part which jcuknz missed out...

    At a given focused distance, DoF is the same for same-sized images, - "at the same f number" regardless of focal length. ie the effective aperture must also be the same.

    Obtaining the same image size with different focal lengths means different shooting distances thus different pictures due tae changed perspective. So not really comparing like with like. DoF, though measurably the same, will probably look different because the foreground/background will be on a different scale in the two shots in proportion with shooting distance.

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    Re: Lenses

    Quote Originally Posted by tao2 View Post
    There is an important part which jcuknz missed out...
    At a given focused distance, DoF is the same for same-sized images, - "at the same f number" regardless of focal length. ie the effective aperture must also be the same.
    I think you are confusing a couple of elements: or at least I donít understand your comment.
    For the DoF to be the same, the FRAMING remains the same - NOT the 'given focused distance'

    ***

    Picking nits: jcuknz also missed out mentioning: camera format.

    But I understood jcuknz response here, to imply, that the Aperture and the Camera Format were to remain the same, just the Focal length of the lens was to change; his words 'given image size' refers to the FRAMING remaining constant.

    ***

    The most appropriate and sensible statements of the Axiom of Depth of Field, that I have found incorporate the following elements:
    • A mention of "Common or Usual Shooting Distances" (i.e. excluding Macro, Close-ups, and Close to Infinity)
    • A mention of common range of Focal Lengths (especially excluding super wide angle lenses)
    • A mention of UNIFORMITY of "Camera Format"
    • A mention of UNIFORMITY of "Aperture"
    • A mention of UNIFORMITY of "Framing"




    For example -

    "For the more common shooting distances and using a common range of lenses the Axiom of Depth of Field states that: provided the Aperture and the Camera Format are the same then the DoF, for all practical purposes, will remain the same for any equivalent framing."

    It is usually useful to also mention DoF is related to, but separate from the quality of Background Blur.

    ***

    The article Kathy linked to (and I read quickly) mentions wide lenses and the asymmetry involved compared to extreme telephoto lenses: but I didn't notice that it mentions Close-up or Macro work.

    The bottom line is: IF you are using (equivalent in 135 Format) lenses from about 20mm to 400mm and making Photographs at Shooting Distances from about 6ft (2mtrs) to 180ft (50mtrs) then knowing the Axiom of DoF can be very useful - especially for Portraiture, where the SD is usually contained to between 6ft and 50ft for those more common FL range of Lenses.


    WW
    Last edited by William W; 1st July 2013 at 04:26 AM.

  20. #20
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    Re: Lenses

    Quote Originally Posted by Alisa View Post
    Hi, Im new to all this photography terminology and what lenses to use. I love taking photos but am struggling with what to use when. If I am taking a photo of single objects, eg. tissue box or an ornament... would it be suitable to use a 90mm? If I get too close with my 55mm its looks warped and I want the background blurred? Thanks.
    Hi Bill,

    You may have understood what jcuknz was saying but Alisa could have formed a wrong impression. See above quote. Not picking nits, being accurate for a (fairly) newcomer to photography...

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