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  1. #1
    Join Date
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    Cool Lens-mount designations ... what do they mean?

    There seems to be a bit of confusion among newer SONY DSLR forum members concerning GRADES OF LENSES and that of Lens-mount designations. If you are new at this (and YOU know who you are ...), there really are a number of questions that need to be answered and you need to be clear about BEFORE you go "lens shopping." All of those letters in the lens names mean something on the lens boxes and this thread is offered to help hash that out, so we are all talking the same SHORTHAND (or coded-jargon), as it were. LOL

    (This is a rough draft ... so you "experienced folks" cut me some slack, will ya? Also, some of this information is somewhat general in nature and can be applicable to other manufacturer camera bodies. in other words ... "please, do read on" ...)

    First things first:

    SONY DSLR (aka Minolta SLR/DSLR) Lens-mounts come in roughly three types. (For a brief history, use this link -> Minolta AF Mount)
    • Film
    • Full-Frame Digital Sensor
    • APS-C Digital Sensor


    Film lenses

    Normally, these lenses are not "digitally coated" ... and were developed before 2003.

    The "digital coatings" are used to reduce and hopefully eliminate light reflections that occur inside the camera body. These reflections occur when the light initially comes through the lens ... hits the shiny digital sensor in the back of the camera, reflects back to the rear element of the mounted lens and then reflects off, scattered, back to the sensor (at the speed of light!). It can cause all sorts of ghostly and ghastly effects, if the light source is strong enough (basically sunlight and flash response).

    Full Frame Digital lenses

    Okay, this where the digital-distinction begins ... so please read through this carefully.

    "Film lenses" and "FF Digital lenses" share a common basic design ... they BOTH have a larger rear element (the last piece of optical glass, in the lens, where the aforementioned digital coatings are done) than the APS-C lenses. That rear element has to present the image circle to cover the entire size of the Full-Frame sensor (which is equivalent to the size of a 35mm-film frame).

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    APS-C Digital lenses

    APS-C lenses are designed to work on APS-C sensors (the SONY Full-Frame camera (currently the α900) is designed to include a "CROP" mode with reduces the FF-sensor to the same image area as the APS-C sensor.) and although they are "graduated" (lenses in mm) in same way as the Full-Frame Lenses, their response on the APS-C sensor is actually a bit different.

    Because the APS-C sensor is smaller, the image circle created by the APS-C lens is smaller to match up with it. SO, if you place an APS-C lens on a Full Frame camera … the APS-C image circle is not large enough to encompass the entire FF sensor and you get a resultant black halo or vignette around your image. If you put the α900 in “Crop” mode, you basically trim-off this vignette and are left with a solid edge around your image.

    Originally termed the "DCF" digital cropping factor, different camera manufacturers had different DCFs with their APS-C line of camera bodies. It is roughly a 1.5 - 1.6x multiplier to the lens you mount. SONY is 1.5x

    Basically, what this means, if you look in the image below ... on a Full Frame camera you get a 50mm image, with a 50mmm lens. On an APC-S Sensor camera body, the very same 50mm image is "cropped" down to what a 75mm lens would see on a Full-Frame camera. An APS-C Sensor simply samples less of the FF- Image Circle.

    Given: the image is taken at the SAME distance from the subject
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    If you have never known a full-frame digital or 35mm-film camera, you would not know about this difference. In fact, using the APS-C camera … you can safely assume that What you see, is what you get (WYSIWYG). Now there is a slight reduction in the viewfinder, so it is possible that the result image you see is going to be about 5% more than what you actually saw. Some of the intro-DSLR cameras … it can be quite a bit more.

    I digress. Back to the mounts and the various manufacturers:

    Different Manufacturers Designations


    SONY

    SONY differentiates their APS-C lenses from the Full Frame lenses by the use of the “DT” designation. “DT” means for use on the APS-C sensor

    TAMRON

    TAMRON differentiates their APS-C lenses from the Full Frame lenses by the use of the “Di-II” designation. “Di” means digitally optimized for use on all SONY/Minolta APS-C, Full-Frame & 35mm-film camera bodies. If there is NO “Di” or “Di-II” designation in the lens’ name, the lens was designed for use on a 35mm-film camera and normally is not rated or suggested for use on a digital sensor body.

    SIGMA

    SIGMA differentiates their APS-C lenses from the Full Frame lenses by the use of the “DC” designation. “DG” means digitally optimized for use on all SONY/Minolta APS-C, Full-Frame & 35mm-film camera bodies. If there is NO “DG” or “DC” designation in the lens’ name, the lens was designed for use on a 35mm-film camera and normally is not rated or suggested for use on a digital sensor body.

    Tokina
    (Currently Tokina does not have the SONY mount in their line-up of lenses, but if they did, it would probably go like this …)
    Tokina differentiates their APS-C lenses from the Full Frame lenses by the use of the “DX” designation. “FX” means digitally optimized for use on all SONY/Minolta APS-C, Full-Frame & 35mm-film camera bodies. If there is NO “FX” or “DX” designation in the lens’ name, the lens was designed for use on a 35mm-film camera and normally is could still be used on a digital sensor body, understanding that it was designed for film use, not digital.

    Overall, do not use the “Di”, “Di-II”, “DC”, “DG”, “DX” or “FX” designations as deciding some type of lens quality. It has nothing to do with that part of the lens, but merely how the lens works with different film bodies.

    You can usually detect lens quality by the retail price you pay for it. Any lens that exceeds the $1000 price point, it is usually considered “professional-level” glass and will be about the best you can obtain in that class lens. They can call it "G" or CZ or whatever, but that dollar amount is usually unmistakable.

    Zoom lenses roughly under $400 price point are consider entry-level lenses and usually have substantial drawbacks for “indoor” use. They, more than likely, will require a flash unit of some substance to render an image faster than 1/30th-second shutter speed.


    SOME EXAMPLES:

    TAMRON SP AF 17-50mm f/2.8 XR Di-II LD Aspherical (IF) <- designed for use on an APS-C Sensor body

    compared to a ...

    TAMRON SP AF 28-75mm f/2.8 XR Di LD Aspherical (IF) <- designed for use on an FF Sensor/35mm-film body & the APS-C sensor ... but, when mounted on a FF camera, the resultant images are proportionally the same as the 17-50mm lens is mounted on the APS-C.
    Last edited by DonSchap; 06-12-2009 at 01:24 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  2. #2
    Join Date
    Jun 2009
    Location
    Mount Pleasant, SC
    Posts
    145
    "Lucy you got some 'splainin' to do" (with my best Cuban accent).
    Now that's what I'm talking about.. Thank You Don I needed this
    Joe Holmes
    Sony α550
    Sony HVL-F42AM Flash
    Sony DT18-55 F3.5-5.6 (Kit Lens)
    Minolta Maxxum 50 1:1.7(22) Prime
    Minolta 35-70 F4 (Mini Beercan)
    Minolta 70-210 F4 (Beercan)
    Minolta 28-135 F4-4.5 (This beast is pretty heavy)
    Minolta Maxxum 100-200 F4.5
    Quantaray D28-90 1:3.5-5.6 Ver 5
    Tamron DiII 55-200 1:4.5-6

  3. #3
    Join Date
    Feb 2006
    Location
    Des Plaines, IL
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    Glad I could be of service ... I hope others get something useful from it.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  4. #4
    Join Date
    Mar 2009
    Location
    San Diego, CA
    Posts
    602

    Explaining lenses

    Don,

    Thanks for explaining in one post what it took me probably a month of reading and comparing to figure out. To bad this wasn't posted last year.

    I still find myself looking at a lens, thinking ... "oh, this looks great, boy would I like to get this lens" ... only to notice its a Sony "DT" a Sigma "DC" or a Tamron "Di-II" and realizing its not for me with my FF a900.

    I would just add that if some of the newer members are looking at "macro" lenses, that not all "macros" are alike. The zoom "macros" generally give a 1:3 ratio versus prime macros which give you a 1:1 ratio.

    Also, if you like great bokeh, you want to look at the number of aperature blades and whether they are circular.
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  5. #5
    Join Date
    Jun 2008
    Posts
    2,204
    Quote Originally Posted by DWessel View Post
    Don,

    Thanks for explaining in one post what it took me probably a month of reading and comparing to figure out. To bad this wasn't posted last year.

    I still find myself looking at a lens, thinking ... "oh, this looks great, boy would I like to get this lens" ... only to notice its a Sony "DT" a Sigma "DC" or a Tamron "Di-II" and realizing its not for me with my FF a900.

    I would just add that if some of the newer members are looking at "macro" lenses, that not all "macros" are alike. The zoom "macros" generally give a 1:3 ratio versus prime macros which give you a 1:1 ratio.

    Also, if you like great bokeh, you want to look at the number of aperature blades and whether they are circular.
    Tamron 70-300mm Di F/4-5.6 gives 1:2 macros. I would consider a 24-70mm CZ next for you
    flickr

    Canon 7D - 5D | 550EX - 430EX II - (2) PW FlexTT5 | 24-105 f4L | 70-200 f2.8L IS | 100 f2.8L IS | 50 f1.8 II

  6. #6
    Join Date
    Dec 2007
    Posts
    1,760
    What ever happened to the good ol days..if it it it worked..lol

  7. #7
    Join Date
    Feb 2006
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    Thumbs up Stepping up to the plate ...

    Quote Originally Posted by DWessel View Post
    Don,

    Thanks for explaining in one post what it took me probably a month of reading and comparing to figure out. To bad this wasn't posted last year.

    I still find myself looking at a lens, thinking ... "oh, this looks great, boy would I like to get this lens" ... only to notice its a Sony "DT" a Sigma "DC" or a Tamron "Di-II" and realizing its not for me with my FF a900.
    Darin,

    I apologize for not taking the "bull by the horns" earlier than now. I know this information is important and to be honest, until last year, most people picking up an A100 or A700 were already film-shooters. Now, with the incursion of newbies via purchases of the intro-DSLRs ... they are strictly "digital novices" with a lot of unanswered questions and no real understanding of the inter-related systems.

    I suspect that with all the questions we have recently been getting on the forum, that someone just had to step up and create some real and decently laid-out responses, so we did not step all over each other trying to hurriedly and accurately answer the poor slob ... and probably confuse that person right out of here.

    By selective use of a couple "sticky threads" ... I have tried to head off this kind of problem and in doing so, maybe answer some nagging questions that other members may have been reluctant to ask or simply did not know how to frame the issue (pardon the pun).

    I have to admit, there is a lot to this ... but some of the answers in books get bogged down in the fact that these guys make money by the weight of the paper ... so they go on and on, explaining every minor detail. As good as that might be, EVERYBODY DOES NOT NEED TO KNOW HOW TO RE-INVENT THE WHEEL. Good Lord, that really gets boring ... and, personally, I want to take images ... not read a ton of reference books. There is a lot to be said from plain old experience.

    In effect ... as long-winded as some of my explanations are, in some cases, they are seriously scaled down compared to what you will be reading in most photography books. There will be a minimum of reading to be a cognizant member of this forum. You just cannot do it well without understanding the 'general' issues in photography. I know I will be called on issues if I put it out incorrectly ... so I try very hard to make sure it is accurate, spelled right ... and edited if I do make an occasional mistake. I try to make the concept rather simple to understand ... make a rough sketch ... nothing too elaborate ... and just hope it gets understood. If I offer an example ... I would hope the inquiring individual would grab up their camera and repeat it, as suggested ... just to understand the principles expressed.

    Practice, baby, practice! The film is free!
    Last edited by DonSchap; 06-13-2009 at 04:29 PM.
    Don Schap - BFA, Digital Photography
    A Photographer Is Forever
    Look, I did not create the optical laws of the Universe ... I simply learned to deal with them.
    Remember: It is usually the GLASS, not the camera (except for moving to Full Frame), that gives you the most improvement in your photography.

    flickr & Sdi

  8. #8
    Join Date
    Mar 2009
    Location
    San Diego, CA
    Posts
    602
    Quote Originally Posted by DonSchap View Post
    Darin,

    I apologize for not taking the "bull by the horns" earlier than now.
    No need. You do wonders for this site.

    Your concept is kind of what I was trying to start with my more broadly worded thread of Flash recommendations for Alpha ... rather than multiple threads created with singular issues like "using a flash with a300."
    Darin Wessel
    α 900
    Zooms: Tamron SP AF70-200mm f2.8 Di LD Macro; Sigma 28-90mm D macro, Konica-Minolta 18-70 f3.5-5.6
    Primes: Minolta 28mm f2.8; Sony 50mm f1.4
    Minolta RC-1000 remote commander

    Film:
    Calumet Cambo CC400 4x5 View Camera
    YashikaMat 6x6 TLR (other accessories)
    Minolta Maxxum 7000 w/ Minolta 35-80mm f/4-5.6 & Minolta 2800 flash
    Minolta Maxxum 5000i & Vivitar 728 AFM flash
    What's next???

  9. #9
    Join Date
    Nov 2008
    Location
    Monmouthshire, UK
    Posts
    2,152
    Good post, Don.
    The only area where I would take issue is the reference to Digital Coatings.
    This is marketing speak designed to encourage people to replace their existing film lenses.

  10. #10
    Join Date
    Dec 2007
    Posts
    1,760
    Don HAS been slacking...

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