[biesnitz]

Hello everyone,

I have recently begun to send more time on indoor macro photography. My current lenses are an older Pentax 50mm macro 1:2 and a Sigma 50mm macro 1:1. Now I am in the market for a 105mm macro ( it would allow me to stand upright by the copy stand and would let more light get on the small objects (coins) I am shooting ). I have cast my eye on a Vivitar series 1 105mm macro but find that this lens is much cheaper with Canon, Nikon, and Minolta mounts than with the rare Pentax mount. I thought of buying a lens with a non-Pentax mount and use a decent glass adapter to fit it on my K-r. Would I be losing much sharpness and quality by this maneuver, or is it a good idea?
I'd be grateful to hear of your experience with mount adapters.

Thanks,
Biesnitz

[boriscleto]

https://www.pentaxforums.com/forums/pentax-camera-field-accessories/96884-ada...addiction.html

[paulusje]

Hello everyone,
I thought of buying a lens with a non-Pentax mount and use a decent glass adapter to fit it on my K-r. Would I be losing much sharpness and quality by this maneuver, or is it a good idea?
I'd be grateful to hear of your experience with mount adapters.

Thanks,
Biesnitz

Let's say you have a nice and sharp macro lens, then those adapters with corrective glass will downgrade the lens to something that is worse than a Canon kitlens

[boriscleto]

Let's say you have a nice and sharp macro lens, then those adapters with corrective glass will downgrade the lens to something that is worse than a Canon kitlens

But for macro use you can remove the glass. It then becomes nothing more than a short extension tube. They even sell the adapters without any glass and labeled for macro use only.

[jatrax]

Might I also suggest you look at one of the Pentax Takumar 100mm macro lenses? They are M42 so the adapter has no optics. Not sure what your budget is but they can be found at good prices if you are patient.

[Lowell Goudge]

If you consider the total set of answers.

you can get a pentax 100mm macro lens (the MF ones are cheap) but they have 2 potential drawbacks , although I dont see this as a problem for shooting coins, unless you are looking at only very small portions of the coin:
- they are generally F4 lenses so the viewfinder can be somewhat dark (pre autofocus I think)
- only the preset takumar and later internally focused macro lenses go to 1:1 without extension tubes.

you can get any other vendor's macro lens and use it with a glassless adapter, typically a 12-14 mm extension tube, and this should not hurt you too badly, except that it may (with a 14mm shift) already put your focusing distance too close (i.,e. too much magnification) for coins

[biesnitz]

Thanks to all for your advice. I did see the glassless adapters, but somehow thought they were inferior to the ones with glass. What I might do - since I am not in a great hurry - is try a non-K mount lens and a glassless adapter, and if the quality is impaired, I will just have to sell the lens again. I did look at Pentax lenses, but except for the last generations, their magnification is 0.5, and as you said, Lowell, they are f/4. I work in daylight, so I would prefer an f/2.8, and I do not want to mess with tubes.

Biesnitz