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With 2 teleconverters would an f5.6 lens be f16?
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PostPosted: Sat Aug 13, 2022 7:09 am    Post subject: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
Got a nice tip in another thread for a fairly lightweight 200mm f5.6 lens with the filter thread to fit an external teleconverter. With a normal teleconverter too, I assume that would make the lens f16 for light? And surely diffraction will damage the image quality on my APSC cameras where it starts becoming an issue after f8 or so?

For now I went for a 135mm f3.5 instead, thinking that would be better in less than perfect light conditions (also I don't have a great 135 already whereas I have a very nice 200mm f4). But I just want to check on the 200mm too, as I am not exactly sure how teleconverters affect lenses' light. Basically I am wondering if that extra reach may make it worth buying to pair with 2 teleconverters.

Thanks.


PostPosted: Sat Aug 13, 2022 9:22 am    Post subject: Reply with quote
Without knowing the focal length multiplier of the "external" TC you mention it is impossible to know what the f/# number would be.

A "regular" 2x TC (i.e. one that fits between the lens and the camera) doubles the f/# number, so an f/5.6 lens would become an f/11 lens. If you add a second 2x TC that would then become an f/22 lens, going into diffraction limitation for APSC.

In essence these conventional type of TC leave the entrance pupil of the lens unchanged, but they double the focal length, hence they double the f/# number.

However, you mention fitting an external TC onto the filter thread of a lens. With these type of TC that go onto the front of a lens it depends very much on the TC design in question as to how it affects the f/# number. If it is a very bulky model that is designed to increase the entrance pupil of the system, the impact on the f/# number may not be all that much.

But beware: whilst the OEM dedicated external TC matched to the particular lens can give excellent results, generic external TCs usually significantly deteriorate image quality.

Whether the image quality when using 2 TCs is still satisfactory depends on your use of the final image; deterioration will be noticeable for sure.


PostPosted: Sat Aug 13, 2022 9:44 am    Post subject: Reply with quote
Probably you get better image quality by simply cropping your image. Easier to use as well, as much more light will enter.


PostPosted: Sat Aug 13, 2022 10:15 am    Post subject: Reply with quote
RokkorDoctor wrote:
Without knowing the focal length multiplier of the "external" TC you mention it is impossible to know what the f/# number would be.

A "regular" 2x TC (i.e. one that fits between the lens and the camera) doubles the f/# number, so an f/5.6 lens would become an f/11 lens. If you add a second 2x TC that would then become an f/22 lens, going into diffraction limitation for APSC.

In essence these conventional type of TC leave the entrance pupil of the lens unchanged, but they double the focal length, hence they double the f/# number.

However, you mention fitting an external TC onto the filter thread of a lens. With these type of TC that go onto the front of a lens it depends very much on the TC design in question as to how it affects the f/# number. If it is a very bulky model that is designed to increase the entrance pupil of the system, the impact on the f/# number may not be all that much.

But beware: whilst the OEM dedicated external TC matched to the particular lens can give excellent results, generic external TCs usually significantly deteriorate image quality.

Whether the image quality when using 2 TCs is still satisfactory depends on your use of the final image; deterioration will be noticeable for sure.


Sorry, forgot to say, the normal is 2x and the one on the end is 1.5x. So I assume it will be f16 instead of f22. But I hadn't notice a change in lighht and IQ, so I will give them a test in the garden. Thanks. 👍


PostPosted: Sat Aug 13, 2022 10:20 am    Post subject: Reply with quote
caspert79 wrote:
Probably you get better image quality by simply cropping your image. Easier to use as well, as much more light will enter.

Very good point. I have been using my old 16MP Fujifilm camera for manual lenses, which I don't like cropping with, but just ordered an M42 adapter for my 24MP Sony, which will be much better for cropping.

Will do a teleconverter battle soon and then decide after checking how they affect IQ. Thanks 👍


PostPosted: Sat Aug 13, 2022 10:28 am    Post subject: Reply with quote
Iq of the lens you are converting is also a major factor. A teleconverter is an optical crop, so an acceptably sharp lens can become soft when tele-converted. small aberrations will be enlarged (apart from any the tc might add). For good results you need good glass and that is usually more expensive, bigger and heavier.

You might look at the Tamron SP 23a 60-300mm 3.8-5.4 http://www.adaptall-2.com/lenses/23A.html as a tele option. It is an exceptionally good yet affordable lens. A lot of reach and if necessary it can be combined with the 01F 2x TC. That will give you a 900mm equivalent reach on APS-C


PostPosted: Sat Aug 13, 2022 12:54 pm    Post subject: Reply with quote
The longest focal length I personally use (on full frame) is 300mm. On a apsc sensor that is about 450mm.

I use a Mamiya-Sekor (645) C 300mm f/5.6, which is arguably one of the best older 300mm lenses you can buy on a tight budget. It’s quite light as well (lighter than the Mamiya SX 300/5.6 for example, despite being a medium format lens).

There are not many legacy 200/300mm lenses that will outresolve your sensor so I would personally not bother with TC’s.


PostPosted: Sat Aug 13, 2022 1:57 pm    Post subject: Reply with quote
caspert79 wrote:
The longest focal length I personally use (on full frame) is 300mm. On a apsc sensor that is about 450mm.

I use a Mamiya-Sekor (645) C 300mm f/5.6, which is arguably one of the best older 300mm lenses you can buy on a tight budget. It’s quite light as well (lighter than the Mamiya SX 300/5.6 for example, despite being a medium format lens).

There are not many legacy 200/300mm lenses that will outresolve your sensor so I would personally not bother with TC’s.

Thank you for the opinions, sounds wise to me. I will have a look for that lens now.


PostPosted: Sat Aug 13, 2022 2:34 pm    Post subject: Reply with quote
D1N0 wrote:
Iq of the lens you are converting is also a major factor. A teleconverter is an optical crop, so an acceptably sharp lens can become soft when tele-converted. small aberrations will be enlarged (apart from any the tc might add). For good results you need good glass and that is usually more expensive, bigger and heavier.

You might look at the Tamron SP 23a 60-300mm 3.8-5.4 http://www.adaptall-2.com/lenses/23A.html as a tele option. It is an exceptionally good yet affordable lens. A lot of reach and if necessary it can be combined with the 01F 2x TC. That will give you a 900mm equivalent reach on APS-C

That is a big lens, looks good but 870g wouldn't get much use with me. I had a similar weighing f4 70-210mm ish Pentax that got sold due to lack of use.

I agree about converting good/bad lenses as I once use a bad Pixar speedbooster on poor edged old lens(es) and it just stretched out the bad edges, which was terrible.

I think I will stick with teleconverters on my 200 and 135 after a battle. Can't today as it is a 50mm vs 55mm vs 55mm battle, and too hot for more. Surprising results with the plain Super Takumar 55 destroying a Super Multi Coated 55 for sharpness and lack of abberations wide open, meaning we have to go into a round of more subjective features.


PostPosted: Sat Aug 13, 2022 2:43 pm    Post subject: Reply with quote
BnG_Murphy wrote:
D1N0 wrote:
Iq of the lens you are converting is also a major factor. A teleconverter is an optical crop, so an acceptably sharp lens can become soft when tele-converted. small aberrations will be enlarged (apart from any the tc might add). For good results you need good glass and that is usually more expensive, bigger and heavier.

You might look at the Tamron SP 23a 60-300mm 3.8-5.4 http://www.adaptall-2.com/lenses/23A.html as a tele option. It is an exceptionally good yet affordable lens. A lot of reach and if necessary it can be combined with the 01F 2x TC. That will give you a 900mm equivalent reach on APS-C

That is a big lens, looks good but 870g wouldn't get much use with me. I had a similar weighing f4 70-210mm ish Pentax that got sold due to lack of use.

I agree about converting good/bad lenses as I once use a bad Pixar speedbooster on poor edged old lens(es) and it just stretched out the bad edges, which was terrible.

I think I will stick with teleconverters on my 200 and 135 after a battle. Can't today as it is a 50mm vs 55mm vs 55mm battle, and too hot for more. Surprising results with the plain Super Takumar 55 destroying a Super Multi Coated 55 for sharpness and lack of abberations wide open, meaning we have to go into a round of more subjective features.


The Super-Takumar will flare a lot more than the S-M-C Takumar. smc coating really brought a mayor improvement in that area.


PostPosted: Sat Aug 13, 2022 4:19 pm    Post subject: Reply with quote
[quote="D1N0"]
BnG_Murphy wrote:
D1N0 wrote:
... it is a 50mm vs 55mm vs 55mm battle, and too hot for more. Surprising results with the plain Super Takumar 55 destroying a Super Multi Coated 55 for sharpness and lack of abberations wide open, meaning we have to go into a round of more subjective features.


The Super-Takumar will flare a lot more than the S-M-C Takumar. smc coating really brought a mayor improvement in that area.


Of course you are right. Massive improvement in the S-M-C version when shooting into the sun. Much better contrast, far less flaring, the colors are really popping too around the garden.

But the older one is sharper and has that lack of ghosting/haze/whatever you call it halo type thing wide open. Slight swirl to the bokeh at the edges.

Both brilliant and imperfect, but that leaves me wanting to buy another 55 instead of selling one. Think I will in case I can find one that is the best of both worlds. Using this page of course to try and get a radioactive one, as I think that may help https://camerapedia.fandom.com/wiki/Radioactive_lenses . My Super Tak 50 is in the middle of these two lenses - good enough to settle on. Pretty sure my long gone first 55 was better than either current 55, so I will keep trying for another near perfect one.


PostPosted: Sat Aug 13, 2022 5:20 pm    Post subject: Reply with quote
[quote="BnG_Murphy"]
D1N0 wrote:
BnG_Murphy wrote:
D1N0 wrote:
... it is a 50mm vs 55mm vs 55mm battle, and too hot for more. Surprising results with the plain Super Takumar 55 destroying a Super Multi Coated 55 for sharpness and lack of abberations wide open, meaning we have to go into a round of more subjective features.


The Super-Takumar will flare a lot more than the S-M-C Takumar. smc coating really brought a mayor improvement in that area.


Of course you are right. Massive improvement in the S-M-C version when shooting into the sun. Much better contrast, far less flaring, the colors are really popping too around the garden.

But the older one is sharper and has that lack of ghosting/haze/whatever you call it halo type thing wide open. Slight swirl to the bokeh at the edges.

Both brilliant and imperfect, but that leaves me wanting to buy another 55 instead of selling one. Think I will in case I can find one that is the best of both worlds. Using this page of course to try and get a radioactive one, as I think that may help https://camerapedia.fandom.com/wiki/Radioactive_lenses . My Super Tak 50 is in the middle of these two lenses - good enough to settle on. Pretty sure my long gone first 55 was better than either current 55, so I will keep trying for another near perfect one.


Which Super Takumar 55? There are 4 different optical formulas among at least 33 version variations.

http://forum.mflenses.com/29-versions-of-the-55mm-asahi-takumar-m42-screw-mount-lenses-t81698.html


PostPosted: Sat Aug 13, 2022 6:01 pm    Post subject: Reply with quote
I have the Super-Takumar first and second version S-M-C SMC and Pentax-K SMC 55.18 On the list for comparisons to be made. But first both Auto-takumars to get. The second one is easy to find cheaply, the first one (Zebra) a bit harder. The First one (just)Takumar 55/1.8 is much harder to find and this to expensive.


PostPosted: Sat Aug 13, 2022 6:09 pm    Post subject: Reply with quote
D1N0 wrote:
I have the Super-Takumar first and second version S-M-C SMC and Pentax-K SMC 55.18 On the list for comparisons to be made. But first both Auto-takumars to get. The second one is easy to find cheaply, the first one (Zebra) a bit harder. The First one (just)Takumar 55/1.8 is much harder to find and this to expensive.


My Zebra Auto-Takumar 1:1.8 f = 55mm has the same optics as my much less expensive Auto-Takumar 1:1.8/55 and Super-Takumar 1:1.8/55 and Super-Takumar 1:2/55...


PostPosted: Sat Aug 13, 2022 6:16 pm    Post subject: Reply with quote
Yeah yeah but but I need all of them :p There is also an all black version of the Auto-takumar V1 Zebra (V2 2 is actually already a Super-Takumar anyway). The Later Super-Takumars are radioactive so They are different because of the thoriated element they contain.


PostPosted: Sat Aug 13, 2022 6:35 pm    Post subject: Reply with quote
D1N0 wrote:
Yeah yeah but but I need all of them :p There is also an all black version of the Auto-takumar V1 Zebra (V2 2 is actually already a Super-Takumar anyway). The Later Super-Takumars are radioactive so They are different because of the thoriated element they contain.


Then there are the 58mm Sonnar, Heliar. and 55mm Gaussian

https://takumarguide.weebly.com/1--2-f58.html
https://takumarguide.weebly.com/1--24-f58.html
https://takumarguide.weebly.com/1--22-f55.html



PostPosted: Sun Aug 14, 2022 9:10 am    Post subject: Reply with quote
[quote="visualopsins"][quote="BnG_Murphy"][quote="D1N0"]
BnG_Murphy wrote:
D1N0 wrote:
... it is a 50mm vs 55mm vs 55mm battle...


Which Super Takumar 55? There are 4 different optical formulas among at least 33 version variations.

http://forum.mflenses.com/29-versions-of-the-55mm-asahi-takumar-m42-screw-mount-lenses-t81698.html


That is an interesting list, thanks for sharing. Pretty sure these are my two 55s:

1963, 1964, Super-Takumar, 1.8, 6/5(2), model I, no 1/2 aperture stop between f/11 and f/16

1971, 1972, Super-Multi-Coated Takumar, 1.8, 6/5(2), with aperture coupling, product 37104

And then I saw:
Quote:
Then there are the 58mm Sonnar, Heliar. and 55mm Gaussian

This is going to get expensive. I should back off while I have the chance, maybe buy a nice Minolta Rokkor before I go down a never endingTakumar hole. 😁


PostPosted: Sun Aug 14, 2022 9:30 am    Post subject: Reply with quote
visualopsins wrote:
D1N0 wrote:
Yeah yeah but but I need all of them :p There is also an all black version of the Auto-takumar V1 Zebra (V2 2 is actually already a Super-Takumar anyway). The Later Super-Takumars are radioactive so They are different because of the thoriated element they contain.


Then there are the 58mm Sonnar, Heliar. and 55mm Gaussian

https://takumarguide.weebly.com/1--2-f58.html
https://takumarguide.weebly.com/1--24-f58.html
https://takumarguide.weebly.com/1--22-f55.html



Yeah I have the Sonnar and the Heliar (in M37) The 5 element 2.2 is pretty rare.


PostPosted: Sun Aug 14, 2022 2:34 pm    Post subject: Reply with quote
Scalpers! Gerjan was kind enough to offer remaining copies of his old edition for iirc $15 as prices on ebay soared. Now there's a newer much better edition available direct:

http://forum.mflenses.com/new-book-on-m42-pentax-and-takumar-is-ready-t81736.html


PostPosted: Wed Aug 17, 2022 12:10 pm    Post subject: Re: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
BnG_Murphy wrote:
Got a nice tip in another thread for a fairly lightweight 200mm f5.6 lens with the filter thread to fit an external teleconverter. With a normal teleconverter too, I assume that would make the lens f16 for light? And surely diffraction will damage the image quality on my APSC cameras where it starts becoming an issue after f8 or so?

For now I went for a 135mm f3.5 instead, thinking that would be better in less than perfect light conditions (also I don't have a great 135 already whereas I have a very nice 200mm f4). But I just want to check on the 200mm too, as I am not exactly sure how teleconverters affect lenses' light. Basically I am wondering if that extra reach may make it worth buying to pair with 2 teleconverters.

Thanks.


Each 2x convert we will double the f number, so it will be f22 and terrible quality, since not only will you be magnifying the aberrations of the lens by 2x, but the aberrations of the front teleconverter as well. Definitely a bad idea

Last edited by kymarto on Wed Aug 17, 2022 6:48 pm; edited 1 time in total


PostPosted: Wed Aug 17, 2022 5:57 pm    Post subject: Re: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
kymarto wrote:


Each 2x convert we will double the f number, so it will be f32 and terrible quality, since not only will you be magnifying the aberrations of the lens by 2x, but the aberrations of the front teleconverter as well. Definitely a bad idea



I don't think so. Front tele/wide converters do not reduce the lens speed (aside glass absorption) unless they have a too small entrance pupil. I have this Raynox, and it does not lower the original speed if not marginally


#1


PostPosted: Wed Aug 17, 2022 6:10 pm    Post subject: Re: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
Ultrapix wrote:
kymarto wrote:


Each 2x convert we will double the f number, so it will be f32 and terrible quality, since not only will you be magnifying the aberrations of the lens by 2x, but the aberrations of the front teleconverter as well. Definitely a bad idea



I don't think so. Front tele/wide converters do not reduce the lens speed (aside glass absorption) unless they have a too small entrance pupil. I have this Raynox, and it does not lower the original speed if not marginally

pic


Put two of those on the front. What then is that system focal length, fastest f/#, and minimum focus distance? Smile How to calculate?


PostPosted: Wed Aug 17, 2022 6:41 pm    Post subject: Re: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
visualopsins wrote:
Ultrapix wrote:
kymarto wrote:


Each 2x convert we will double the f number, so it will be f32 and terrible quality, since not only will you be magnifying the aberrations of the lens by 2x, but the aberrations of the front teleconverter as well. Definitely a bad idea



I don't think so. Front tele/wide converters do not reduce the lens speed (aside glass absorption) unless they have a too small entrance pupil. I have this Raynox, and it does not lower the original speed if not marginally

pic


Put two of those on the front. What then is that system focal length, fastest f/#, and minimum focus distance? Smile How to calculate?


I don't think you could calculate that easily without doing some measurements. Clearly the TC shown has a much smaller diameter rear thread than front thread, so when stacking two of those almost certainly the exit pupil of the front TC would not be adequate to cover the entrance pupil and full FOV of the rear TC; likely both loss of illumination and heavy vignetting would occur.


PostPosted: Wed Aug 17, 2022 6:55 pm    Post subject: Re: With 2 teleconverters would an f5.6 lens be f16? Reply with quote
visualopsins wrote:
Ultrapix wrote:
kymarto wrote:


Each 2x convert we will double the f number, so it will be f32 and terrible quality, since not only will you be magnifying the aberrations of the lens by 2x, but the aberrations of the front teleconverter as well. Definitely a bad idea



I don't think so. Front tele/wide converters do not reduce the lens speed (aside glass absorption) unless they have a too small entrance pupil. I have this Raynox, and it does not lower the original speed if not marginally

pic


Put two of those on the front. What then is that system focal length, fastest f/#, and minimum focus distance? Smile How to calculate?


I meant the front of two rear converters. My experiences with front converters is not good, and it gets proportionally worse the longer the lens. Even one front converter on a 200mm will be abysmal, and add a rear converter and you are talking beyond the pale awful.


PostPosted: Wed Aug 17, 2022 9:46 pm    Post subject: Reply with quote
I only was answering to the opener's request, a front teleconverter + a rear one; the first does not change the F, just a little the T value. I didn't say that the quality is good or not, but I have to say that my Raynox (not a cheap one, its pricelist was over 300 euros, and it fits 5 elements) is not bad at all with the right lenses
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