What would happen if I were to use a crop lens with tc on the K1?

pschlute · 10-02-2017, 10:19 PM - **2 Likes**

As Bob pointed out, whether you use crop mode or FF mode the image quality will be the same on the K1 for that portion of your image not suffering from vignetting.

So your question is really "will a 50mm +TC make a good portrait combo" ? From a FL perspective the answer is yes. But you will lose light, and depending on the quality of the TC maybe image quality too. The K1 produces very good images and you may be surprised how much further you can crop them compared to what you are using now. So maybe just try the 50 on its own.

automorphism · 10-03-2017, 03:45 AM

You should just use the 50mm on full frame and use crop mode if you want a similar field of view as an APS-C. No need for the TC.

leekil · 10-03-2017, 11:02 PM - **1 Like**

Originally posted by NoCo Pentaxian

I think the solution is obvious: Pentax needs to make a 0.5x teleconverter for the K1 that would disperse the light from crop lenses onto a full frame sensor. (j/k)

It would seem that a 1.5x TC made for full frame would do exactly that...

---------- Post added 10-03-17 at 11:03 PM ----------

Here; by the way, is a previous thread regarding the HD teleconverter and the OP's original question, with photos even:

Use of 1.4x rear converter improve compatibility of DA lenses with K-1 full frame? - PentaxForums.com

TheOneAndOnlyJH · 10-05-2017, 02:24 PM - **1 Like**

Originally posted by leekil

Here; by the way, is a previous thread regarding the HD teleconverter and the OP's original question, with photos even:
Use of 1.4x rear converter improve compatibility of DA lenses with K-1 full frame? - PentaxForums.com

The pictures in that thread show it's possible, but they don't show if it really helps vs. shooting in crop mode without the TC. Someone would have to do a direct comparison to see if the extra resolution gained by enlarging the image on the sensor outweighs the IQ degradation caused by the TC. Even if a DA lens + TC combo doesn't cover the whole full frame it might still show more detail than using a lens in crop mode.

Let's say that the K-1 with an APS-C lens + TC has bad edges and cropping them off would give a 28MP image. Is that extra resolution useful, or does the TC degrade IQ to where it's worse than if you had just used the lens in 16MP crop mode? I could see if the TC is good enough, you might be able to get more detail out of a crop lens by using a TC in FF mode.

I could see this also being particularly relevant if you're deciding between the K-3 and K-1 and only have APS-C lenses. Is that 36MP or cropped 28MP better than the 24MP you would get mounting that same lens on the K-3, or does the TC degrade IQ enough that the additional resolution is negated?

Unfortunately I don't have a K-1, but if someone would be happy to volunteer images, how about the following shots taken from the same position and same settings? (same zoom, aperture, ISO, etc):

K-1 + DA lens + TC in 36MP FF mode
K-1 + DA lens in 16MP crop mode ("K-5 equivalent")
(K-3 + DA lens wouldn't hurt if you have one)

This would help answer whether the increase in resolution outweighs IQ degradation. Of course it will probably vary for each crop lens or TC, but at least it would be a start.

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10-02-2017, 10:19 PM - 2 Likes	#16
pschlute Moderator Loyal Site Supporter Join Date: Mar 2007 Location: Surrey, UK Photos: Gallery Posts: 8,198	As Bob pointed out, whether you use crop mode or FF mode the image quality will be the same on the K1 for that portion of your image not suffering from vignetting. So your question is really "will a 50mm +TC make a good portrait combo" ? From a FL perspective the answer is yes. But you will lose light, and depending on the quality of the TC maybe image quality too. The K1 produces very good images and you may be surprised how much further you can crop them compared to what you are using now. So maybe just try the 50 on its own.

10-03-2017, 03:45 AM	#17
automorphism Veteran Member Join Date: Jun 2015 Location: Ontario, Canada Photos: Albums Posts: 791	You should just use the 50mm on full frame and use crop mode if you want a similar field of view as an APS-C. No need for the TC.

10-03-2017, 11:02 PM - 1 Like	#18
leekil Pentaxian Join Date: May 2016 Photos: Albums Posts: 2,003	Originally posted by NoCo Pentaxian I think the solution is obvious: Pentax needs to make a 0.5x teleconverter for the K1 that would disperse the light from crop lenses onto a full frame sensor. (j/k) It would seem that a 1.5x TC made for full frame would do exactly that... ---------- Post added 10-03-17 at 11:03 PM ---------- Here; by the way, is a previous thread regarding the HD teleconverter and the OP's original question, with photos even: Use of 1.4x rear converter improve compatibility of DA lenses with K-1 full frame? - PentaxForums.com

10-05-2017, 02:24 PM - 1 Like	#19
TheOneAndOnlyJH Veteran Member Join Date: Dec 2013 Location: Buffalo, NY Posts: 351	Originally posted by leekil Here; by the way, is a previous thread regarding the HD teleconverter and the OP's original question, with photos even: Use of 1.4x rear converter improve compatibility of DA lenses with K-1 full frame? - PentaxForums.com The pictures in that thread show it's possible, but they don't show if it really helps vs. shooting in crop mode without the TC. Someone would have to do a direct comparison to see if the extra resolution gained by enlarging the image on the sensor outweighs the IQ degradation caused by the TC. Even if a DA lens + TC combo doesn't cover the whole full frame it might still show more detail than using a lens in crop mode. Let's say that the K-1 with an APS-C lens + TC has bad edges and cropping them off would give a 28MP image. Is that extra resolution useful, or does the TC degrade IQ to where it's worse than if you had just used the lens in 16MP crop mode? I could see if the TC is good enough, you might be able to get more detail out of a crop lens by using a TC in FF mode. I could see this also being particularly relevant if you're deciding between the K-3 and K-1 and only have APS-C lenses. Is that 36MP or cropped 28MP better than the 24MP you would get mounting that same lens on the K-3, or does the TC degrade IQ enough that the additional resolution is negated? Unfortunately I don't have a K-1, but if someone would be happy to volunteer images, how about the following shots taken from the same position and same settings? (same zoom, aperture, ISO, etc): K-1 + DA lens + TC in 36MP FF mode K-1 + DA lens in 16MP crop mode ("K-5 equivalent") (K-3 + DA lens wouldn't hurt if you have one) This would help answer whether the increase in resolution outweighs IQ degradation. Of course it will probably vary for each crop lens or TC, but at least it would be a start.