Using K-mount lenses on a Pentax DSLR.

Hello Robert, I am not a Pentax user but I suspect that the K-50 (like most DSLRs) is sold with a standard kit lens at a price which is often only a little greater than the price of the body alone. The kit lens in this case is the 18 - 55  mm Pentax DAL zoom lens, covering moderate wide-angle to modest telephoto. Even if you buy this lens separately, it can be bought in a white box (split from the kit) at under £49. Such a kit lens will not be professional quality, but is perfectly OK for most travel photos. 

I agree it would be an interesting experiment to try your older lenses, but I suspect it would be laborious and time-consuming to manually focus and take the exposure reading. Also, you may well find that the older lenses are not as sharp as you might hope. The resolution of the 16 MP digital sensor of the K-50 will be less forgiving than film emulsion. To conclude, by all means try the older lenses, but I think you will get 'hooked' by the ease and  convenience of the newer lenses. Start with the 'kit' lens and I think you may want to add other lenses in due course. Not all of them break the bank. I hope also you will be able to persuade your wife to visit England.

Hello Edward; I am stuck in my ways using manual lenses. I thought about the pixels being a factor in the results. Film speed was graded by the size of the grains and this determined the speed of the film. I supposing that the pixels will be similar. My favorite lenses are just two zooms, a 35-70 and a 70-210, I used a 400 once in a while. My pet lens is 35-70. These lenses for Digital use are priced high and their widest opening is too much for my use. I have priced used lenses and unless I can actually test the lenses I am concerned about buying a bad lens. Pentax makes very good products and I believe their "glass" was as close to perfect as possible. The "kit" lens would be great for general picture taking, birthdays, holidays etc. I have a lot to learn concerning digital photography and I look foward to getting heavily involved in out door photography. It's just that living on limited means I have to get the equipment that will let me enjoy my hobby without breaking the bank. I would like to know what the formula is for converting the digital lens into what it would be in 35mm.

Sincerely,                                                                                   Bob Speicher

Hello again Bob, If you are set on the K-50, I think it's worth having a go with the kit lens that comes at virtually zero cost. Regarding focal length etc, the important thing is sensor size relative to the area of film in a film camera. I think the sensor in the K-50 is APS-C size. This is about 1.6X smaller than the area of 35mm film, giving a  focal length conversion factor of 1.6X magnification. This means that the 18 - 55 mm kit lens on the K-50 has the same angle of view as a 29 - 88 mm lens on a film camera. There is no difference in actual focal length of the lens, it is just that the sensors in most DSLRs crop the image circle relative to what the 35 mm film would see, giving a narrower angle of view and an apparent magnification.

The difficulty with using 'Film Era' lenses on crop-sensor DSLRs, apart from issues of focussing and metering, is that the lenses designed for use with film are generally not 'wide' enough on digital. For example, fitting your old 35 - 70 zoom onto a K-50 will result in an angle of view equivalent to  56 - 112 on a film camera. This, in my opinion,  is not a very useful focal length range. 

Bear in mind though, that DSLR sensors come in different sizes. I currently use a Canon EOS 5D, which has a large sensor, the same size as the 35mm film area.  In the case of these 'full frame' cameras, the angle of view is exactly the same as it would be on a film camera, and no correction of focal length is necessary. A 28 mm lens stays as wide as it would be on a film camera. The downside of  full-frame cameras is cost and weight, but the older full frame cameras are now becoming quite affordable. A used Canon EOS 5D Mark 1 now sells for £400 - £500 in the UK and is a great camera. Unfortunately, for the Pentax user, there isn't a full-frame Pentax.

This Wikipedia Article on Crop Factor might be helpful. 

Interesting comments from you guys, but some of it way above my head as I still use a Brownie! lol

Well done Edward and Bob!

LOL @ Ron, times have changed, you know.

In the old days, exposure meters didn't exist and you judged the exposure settings from the instructions on the film box - 1/125 at f/11 for Sunny Skies, f/8 for Bright Cloudy Skies, f/5.6 Cloudy Skies etc. The results were not always good, however.

There is plenty of opportunity for brain work in Digital Photography, although as Bob says, you can set everything to 'Auto'  if you wish, and let the camera do the thinking for you.