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K5iis and Vivitar Series 1 70-210

Discussion in 'Pentax Chat' started by Shovelheadstroker77, Jul 16, 2013.

  1. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    Hi - having taken the leap and purchased my K5iis I am know getting to grips with various lenses. Its been a while since I used an SLR and I seem to have forgotten quite a lot. Currently exploring a mint Vivitar Series 1 70-210 which I picked up on ebay - but I am confused. It is fixed aperture, 1:3.5 inscribed on the top of the lens, (which in my mind means the aperture is fixed ie cannot be changed) but it has 22 to 3.5 aperture ring at the bottom which changes the aperture . So what exactly is the fixed aperture aspect referring to. This is daft laddi question I know but I have spent ages searching on the net for an explanation so thought I would now ask "those who know". I look forward to your explanations! -I think I should change my user name to extreme novice! Stephen
  2. Done_rundleCams

    Done_rundleCams AP Forum Ambassador to Canada

    Hi S_H_S,

    The f/3.5 means that, in theory, the aperture, if set to 3.5, will remain at that all the way through the zoom range. It can, of course, be changed/closed down should you require a smaller aperture setting (f/5.6,8,11,etc...) :)

    Also, if it is an A-series lens (with an A just after the f/22 setting) means that you can use your K-5IIs in Program mode if you lock the lens in the A setting :)

    If it not's an A series, then you'll set the Custom Function #27 ..

    Hope this helps a wee bit :)


    Last edited: Jul 17, 2013
  3. Roy5051

    Roy5051 Well-Known Member

    As DRC says, it is not a FIXED aperture, it is a CONSTANT aperture, meaning you can use f/3.5 at every focal length if you want to. Unlike most cheaper modern zooms, where the aperture may be described as f/3.5-5.6, where the maximum aperture at its shorter focal length is f/3.5 and at its longer focal length is f/5.6. This makes the old Vivitar much more usable, especially in lower light at longer focal lengths.
  4. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    Thank you Jack & Roy, brilliant- I now understand that fully. Onwards and upwards! cheers Stephen :eek:
  5. Done_rundleCams

    Done_rundleCams AP Forum Ambassador to Canada

    Go get 'em Stephen :D

    Cheers and good shooting :)

  6. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    inevitable that another question would pop along --- I am toying with either buying a Pentax DA 55-300 mm f/4.0-5.8 SMC or a Pentax SCM F 100-300. The latter is a film lens so I presume on my K5 it would be the equivalent of 150-450mm . The DA is a digi lens though. So am I correct in concluding that the SCM F will give me more reach or are the mm given on digi lenses also in old money as well? Not sure if I have asked that question in a very clear way- bottom line - will the F give me more zoom than the DA? - thanks Stephen
  7. Benchista

    Benchista Which Tyler

    Well the DA will give you more zoom, because what that really means is the difference in focal lengths. As to which will give you more reach, they're identical - the focal length is an intrinsic property of the lens that doesn't actually change - both lenses are as quoted, and any 300mm focal length lens will perform the same on a given body - on a Pentax DSLR, they will both give the same angle of view as a 450mm lens would on film or full frame.
  8. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    Thanks Ben - right lets see if I have got this right - I have now got the zoom bit sorted out in my head ie the DA will give me more as it has a bigger range ie 245mm variation compared to 200mm variation of the F. So "reach" was the term I was struggling to identify. However, I am still not completely clear. As the F at 300mm means the lens would be 300mm from the film at full reach, but on a digi it would be approx at 450mm between lens and sensor at full reach, so if manufactured now for a digi camera the F stated spec on the lens would be 150mm to 450mm. My thinking still tells me that as the DA is a digi lens then the mm quoted will be for distance between the lens and the sensor ie 300mm - so the F will give me more reach as in digi terms it maxes at 450mm as opposed to 300mm? - is that correct? or am I still missing something? Thanks for your time explaining these things. Stephen
  9. Benchista

    Benchista Which Tyler

    No; 300mm is 300mm, whatever it was designed for. On cropped sensor digital, both lenses will give the same effect - they won't actually be 450mm, but they will give the same view as a 450mm lens would do on film.
  10. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    Still to understand this, but the penny will drop so please bear with me Nick - maybe if I approach it from another angle with the following question - on digital lenses what does the mm measurement refer to? -is it the distance between the lens and the sensor or the distance between the lens and where the film would be if it was on a film camera? If it is the latter then I understand how and why a 300mm is 300mm, irrespective of whether it was made for film or digi, and how on a digi body it will give the equivalent of a 450mm field of view experienced with 450mm lens on a film camera. If not then I am still stuck and think I'd better go read some camera books? -recommendations for which are welcome! Best wishes Stephen PS it was the statement in this add on ebay http://www.ebay.co.uk/itm/Pentax-SM...06&rk=1&rkt=6&sd=400488301030&#ht_1992wt_1018 which made me think this film F lens would give me more reach on my K5iis (although they use the term zoom!!) than a digi 300mm lens.
    Last edited: Jul 17, 2013
  11. Benchista

    Benchista Which Tyler

    The focal length is a property of a lens that frankly isn't directly useful to photographers - in itself, it doesn't really tell you that much. What we as photographers really care about is the angle of view - how much of a scene is included on the film/sensor, and how big a subject appears (relative magnification). That does depend on the focal length, but also on the physical size of the format in use. So if there's a 300mm lens, it will ALWAYS be a 300mm lens on any format, but the angle of view will be different, as will the relative magnification. The shorthand we have used as photographers is to compare the effect of a lens we get to what we had with lenses used with 35mm. The "crop factor" is measured by the factor of the diagonal measurement of the sensor compared to that of 35mm film. The factor for Pentax DSLRs is 1.5x, meaning that ANY focal length used on one of these cameras will give an angle of view and relative magnification as a lens with 1.5x the same focal length on 35mm or full frame digital.

    In all honesty, you probably don't really need to know this if you don't want to (and a lot of web sites get this badly wrong), but the important thing to know is that for any lenses you can fit to your DSLR, the marked focal lengths are actual ones and can be directly compared with each other, but the effect you'll get on your DSLR will be of a lens 1.5x the focal length when compared to using the same lens on 35mm film or a "full frame" digital format. So both lenses have a 300mm top end, and both will give you the effect of a 450mm lens on your camera - it's the sensor size that makes the difference, not which format the lens was designed for.
  12. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    ok - penny has dropped and I have learnt something new to day which makes it a worthwhile day! Basically there is no difference between what is being measured to give the x mm measurement on a lens made for film or digi (that is because the mm is a measurement of the focal length which is a physical property of the lens and nothing to do with the orientation of the lens relative to the camera), it is just on a digi (unless full frame?) that orientation is different ie the sensor is closer than the film would be so it only picks up a cropped version of what a film would pick up resulting in a field of view of y and associated relative magnification. To achieve the same on a film (or full frame digi?) you would need to use a lens of x * 1.5 mm. Sorted. So take home message re the important practical implications of this is that digi camera's provide more reach (or relative magnification) with any size of lens than if it was used on a 35mm camera. You are right, I probably did not need to know that but my brain is such that I need to understand these things! Thanks for your perseverance! cheers Stephen :)
  13. El_Sid

    El_Sid Well-Known Member

    Er... no...

    The sensor in an APS-C format DSLR is exactly the same distance from the lens as a full frame digital or film model, it has to be or the lens won't focus properly. The crop factor arises from the sensor being physically smaller than either the 35mm film frame or full frame sensor.

    35mm film/full frame digital has a frame size of 36 x 24mm (roughly 1.5 x 1 inch) while the APS-C sensor is approximately 22 x 15 mm (it varies by maker), this means that when the image is printed to a given size the image from the APS sensor is magnified more than that from full frame - ie if you print 35mm full frame image as a 6 x 4 inch print the magnification is just about 4x but if you print an APS image to the same size the magnification is roughly 6x (smaller sensor you see) which is what gives the impression of increased focal length.
  14. Shovelheadstroker77

    Shovelheadstroker77 Active Member

    funny old business this -I was thinking about this thread when driving home from work just now and, having thought I had put my mind to rest on the subject last night - thought "no that cannot be correct as it would not focus properly!" - at some stage a colleague gave me some duff info about the sensor being further forward than a film surface etc. So that is what started all these hares running in my mind. However, I now fully understand. Thanks for the conformation Nigel - it was timely and saved me spending hours again tonight on this forum trying to confirm things. Happy snapping - I am sure there will be further Q in the future. Best wishes Stephen

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