Adapter or legacy glass?

**Michail_P** · 02-02-2020, 11:42 AM

So I am considering the use of my FD lenses with an adapter for my k-70. I have heard from friends that due to the infinity focus issue it is not worth taking the risk. Instead, I could get some decent legacy prime glass. Thing is I really like my FD lenses. So my question is how much of an issue is the compromise on image quality? Is it something noticeable? I’m currently looking at fotodiox, because recently my experience with cheaper unbranded options is not that good. My work is not professional but the actual dilemma lies in the cost.

Bertrand3000 · 02-02-2020, 11:59 AM

Well, if you use an adapter without glass, image quality won't be affected. If infinity focus is lost due to flange distance, then you won't be able to focus to infinity, but for anything closer than that, it should be fine. Beware of potential lost of automation (like autofocus or aperture control), it depends on adapter and lens (I have no experience with FD lenses).

If an adapter uses glass to restore infinity focus, image quality will be affected. Difficult to say how much without knowing lens and adapters involved.

richfam · 02-02-2020, 12:24 PM - **1 Like**

If you use the Fotodiox adapter to mount FD lenses on your K-70, the resulting image quality will ghastly; I know, because I tried it. The adapter is basically a 1.4x teleconverter using just a single glass element, so sharpness & contrast are totally trashed... and the combination of 1.4x and the APS-C crop means that a 20mm ultrawide becomes equivalent to a 42mm full frame lens. If you remove the glass element, then the adapter will work really well as a short extension tube for macrophotography with your FD lenses, but they won't focus infinity. Good teleconverters usually contain multiple glass elements and cost far more than the Fotodiox adapter.

**Michail_P** · 02-02-2020, 02:13 PM

Thanks for the response guys! Guess I’ll have to either compromise or get some ideas for old lenses. Or I could eventually use both. For now I am gonna be looking for a prime. A nice nifty fifty maybe. I love my FD 50 1.8... something to replace maybe.
Any suggestions for a 24-35 range primes?

ChristianRock · 02-02-2020, 09:33 PM

You really need to try some nifty fifties from Pentax and Ricoh (Rikenon). I bet you won't miss your FD 50 1.8 too much.
I know, I have had a few and still have 9...

**Papa_Joe** · 02-03-2020, 09:27 AM - **1 Like**

I'am sorry to tell you, but there is no use in trying to adapt lenses with a shorter flange focal distance to cameras with a longer one. You will always be unhappy with the results in one (no focus to infinity) or another (worse IQ) way. It might be a solution for a single lens to play around with, but with a whole set of lenses I would recommend to get a camera with a shorter flange focal distance. They way to go is a mirrorless camera. This might be a cheap old MFT or a new one of the known manufacturers but you will be better of with one of these then meddling around with a K-70. Whereas, if you take it seriously an electronic viewfinder is recommended.

If you want to use legacy lenses on your K-70 you should go for lenses with K- (no automatic) or KA- (automatic exposure) mount. Pentax M (K-mount) lenses are quite inexpensive, not to say a bargain.

02-02-2020, 11:42 AM	#1
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006	Adapter or legacy glass? So I am considering the use of my FD lenses with an adapter for my k-70. I have heard from friends that due to the infinity focus issue it is not worth taking the risk. Instead, I could get some decent legacy prime glass. Thing is I really like my FD lenses. So my question is how much of an issue is the compromise on image quality? Is it something noticeable? I’m currently looking at fotodiox, because recently my experience with cheaper unbranded options is not that good. My work is not professional but the actual dilemma lies in the cost.

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02-02-2020, 11:59 AM	#2
Bertrand3000 Veteran Member Join Date: Feb 2019 Posts: 2,009	Well, if you use an adapter without glass, image quality won't be affected. If infinity focus is lost due to flange distance, then you won't be able to focus to infinity, but for anything closer than that, it should be fine. Beware of potential lost of automation (like autofocus or aperture control), it depends on adapter and lens (I have no experience with FD lenses). If an adapter uses glass to restore infinity focus, image quality will be affected. Difficult to say how much without knowing lens and adapters involved.

02-02-2020, 12:24 PM - 1 Like	#3
richfam Forum Member Join Date: Oct 2017 Location: Lindsborg, Kansas Photos: Gallery Posts: 89	If you use the Fotodiox adapter to mount FD lenses on your K-70, the resulting image quality will ghastly; I know, because I tried it. The adapter is basically a 1.4x teleconverter using just a single glass element, so sharpness & contrast are totally trashed... and the combination of 1.4x and the APS-C crop means that a 20mm ultrawide becomes equivalent to a 42mm full frame lens. If you remove the glass element, then the adapter will work really well as a short extension tube for macrophotography with your FD lenses, but they won't focus infinity. Good teleconverters usually contain multiple glass elements and cost far more than the Fotodiox adapter.

02-02-2020, 02:13 PM	#4
Michail_P Site Supporter Join Date: Nov 2019 Location: Kalymnos Photos: Gallery Posts: 3,006 Original Poster	Thanks for the response guys! Guess I’ll have to either compromise or get some ideas for old lenses. Or I could eventually use both. For now I am gonna be looking for a prime. A nice nifty fifty maybe. I love my FD 50 1.8... something to replace maybe. Any suggestions for a 24-35 range primes?

02-02-2020, 09:33 PM	#5
ChristianRock Pentaxian Join Date: Jul 2013 Location: People's Republic of America Photos: Gallery \| Albums Posts: 9,910	You really need to try some nifty fifties from Pentax and Ricoh (Rikenon). I bet you won't miss your FD 50 1.8 too much. I know, I have had a few and still have 9...

02-03-2020, 09:27 AM - 1 Like	#6
Papa_Joe Site Supporter Join Date: Sep 2018 Location: SW Bavaria Posts: 562	I'am sorry to tell you, but there is no use in trying to adapt lenses with a shorter flange focal distance to cameras with a longer one. You will always be unhappy with the results in one (no focus to infinity) or another (worse IQ) way. It might be a solution for a single lens to play around with, but with a whole set of lenses I would recommend to get a camera with a shorter flange focal distance. They way to go is a mirrorless camera. This might be a cheap old MFT or a new one of the known manufacturers but you will be better of with one of these then meddling around with a K-70. Whereas, if you take it seriously an electronic viewfinder is recommended. If you want to use legacy lenses on your K-70 you should go for lenses with K- (no automatic) or KA- (automatic exposure) mount. Pentax M (K-mount) lenses are quite inexpensive, not to say a bargain.