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06-13-2022, 02:08 AM   #31
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QuoteOriginally posted by Paul the Sunman Quote
Pentax full frame teleconverter
For use with long glass, manual focussing can be an advantage is some situations. That being the case, there are some Pentax options available on the preowned market, namely... Rear Converter-A 1.4x-S, Rear Converter-A 1.4x-L, Rear Converter-A 2x-S and Rear Converter-A 2x-L (review links listed bellow) which may offer you a solution.

Rear Converter-A 1.4x-S Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

Rear Converter-A 1.4x-L Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

Rear Converter-A 2x-S Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

Rear Converter-A 2x-L Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database

06-13-2022, 02:22 AM - 1 Like   #32
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Can someone explain to me why using a teleconverter on a full frame body could be better than putting the same lens on a crop body? With the latter there are no extra optical elements in the way and you don't lose a stop of light.

Just get the crop converter
06-13-2022, 11:35 AM - 2 Likes   #33
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If I had a k1, these would be the reasons I would use it. They already apply with my ks-2 and 1.4x.

reason 1 is you may be able to fill a bigger frame if you can get close enough.

reason 2 is if you can fill the frame you get more pixels. This also gives you the option to downsize to the crop sensor size and reduce the stop of noise to par with just cropping.

reason 3 is to change lenses in the field without exposing the sensor to the elements.

resaon 4 is to make my macro a 1.4:1 macro or give me working distance at 1:1. giving the extra magnification at minimum focusing distance already makes my 55-300PLM great for 1:2 like butterflys.

There is a sweet spot between number of pixels and the fuzzy discs the lens produces given the pixel size of the sensor. Crop too much and at viewing size you enlarge the discs too much. Crop too little and your subject is lost in the frame. At the same time if you crop, you also magnify the noise as you have to magnify the viewing size.

It certainly isn't a perfect way. It is just one way of implementing compromises like all the rest and has some advantages and some disadvantages.
06-13-2022, 02:44 PM   #34
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QuoteOriginally posted by swanlefitte Quote
If I had a k1, these would be the reasons I would use it.
Thanks for that. They aren't things I had considered.

06-13-2022, 03:23 PM   #35
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Have you tried the 1.7x? SMC Pentax-F 1.7x AF Adapter Reviews - Pentax K-mount Teleconverters and Adapters - Pentax Lens Reviews & Lens Database
It pairs well with the misnamed SMC Pentax-DA* 300mm F4 ED [IF] SDM Reviews - DA Prime Lenses - Pentax Lens Reviews & Lens Database
(the DA star 300mm is really a full frame lens, but it came out before they had the DFA nomenclature).
06-13-2022, 03:42 PM   #36
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QuoteOriginally posted by Sandy Hancock Quote
an someone explain to me why using a teleconverter on a full frame body could be better than putting the same lens on a crop body? With the latter there are no extra optical elements in the way and you don't lose a stop of light.

Just get the crop converter
When using a 1.4 TC on a FF camera will put nearly the same amount of light as one using a 1.5 cropped body

The best way to look at it is that with the cropped body you are using ruffle the same area of the image circle from the lens same amount of light coming from the lens, with the TC you are cropping it optically.
With the FF using a TC and you are not shutter speed limited you can use a longer shutter speed over the cropped camera body for a cleaner image, you also have a higher pixel count
06-13-2022, 05:08 PM - 1 Like   #37
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QuoteOriginally posted by Ian Stuart Forsyth Quote
When using a 1.4 TC on a FF camera will put nearly the same amount of light as one using a 1.5 cropped body
No, you lose a stop, Ian.

This is the mistake Equivalence people make. All the time.

06-13-2022, 05:45 PM - 1 Like   #38
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QuoteOriginally posted by clackers Quote
No, you lose a stop, Ian.

This is the mistake Equivalence people make. All the time.
No, you get it back in sensor area.
Either the light is distributed over a small area with low f number or over a large area with higher f number. With the same field of view, the total light is the same.

Here's another way to see it, I have a 0.7 "reducer" that gets me more light because the full frame image captures a wider field of view. It converts my 2350mm f10 mirror lens into a 1650mm f7.
06-13-2022, 08:18 PM   #39
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QuoteOriginally posted by clackers Quote
This is the mistake Equivalence people make. All the time.
Its 1 to 1 comparison
Ya simple math gets it wrong all the time, Half the density of light over a area that is 2 times larger is not equal to twice the density of light over an area 1/2 of its size
0.5 X 2 = 2 X 0.5
1=1
06-13-2022, 09:02 PM   #40
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QuoteOriginally posted by Ian Stuart Forsyth Quote
With the FF using a TC and you are not shutter speed limited you can use a longer shutter speed over the cropped camera body
Ah, but there's the rub. We frequently are shutter speed limited. Regardless of the total number of photons shining up the wazoo, the intensity of that light is the same. So you if you shoot a FF camera with a teleconverter you have to sacrifice a stop of shutter speed or ISO to keep the exposure the same compared to a crop camera with the same lens and no teleconverter.

Yes, I grant you that a full frame sensor might give you more ISO latitude, but with the Pentax K-3 III vs the K-1 II I'm not sure there's not much in it.

Anyway, it's all a bit academic. There is no modern FF teleconverter for the K-1, and none on the horizon, so I would suggest the HD Pentax-DA 1.4x AW AF Rear Converter on the K-3 III is probably the best way to maximise reach in the Pentax ecosystem.
06-13-2022, 09:22 PM   #41
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QuoteOriginally posted by Sandy Hancock Quote
So you if you shoot a FF camera with a teleconverter you have to sacrifice a stop of shutter speed or ISO to keep the exposure the same compared to a crop camera with the same lens and no teleconverter.
Tell me first why it is important to keep the same exposure, and second why a person should not compare the amount of light as that is the determining factor in how much noise a person will see. If I am using a 1.4 tc or a cropped body they record the same amount of noise and under some conditions will record less noise
What would I choose, packing a 1.4 tc for added reach when needed or the burden of the additional camera body and the larger cost of that body for the very same reach.
06-14-2022, 01:11 AM   #42
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QuoteOriginally posted by Sandy Hancock Quote
Can someone explain to me why using a teleconverter on a full frame body could be better than putting the same lens on a crop body? With the latter there are no extra optical elements in the way and you don't lose a stop of light.

Just get the crop converter
The reason for having a convertor attached to a telephoto lens objective is the same old one: to magnify the object as much as possible, and to be able to obtain a more detailed image with wider contrast range. Unfortunately, unlike an architecture or family members most wildlife (except for some predators) often moves away from a photographer ,or at least keeps at certain minimal distance. The current Pentax telephoto "line-up" consists of two 55-300mm and 300mm prime for a crop sensor, and one (very good !) full frame zoom of "150-450mm". The crop sensor telephoto zooms are good only for shooting animals inside small cages in a zoo (only if the place is not too crowded and one can get close enough to a cage mesh ....) The 300mm crop sensor prime , on the other hand, may provide decent image quality if combined with this modern 1.4x teleconverter in condition that an object is large enough (chicken size bird) and is not farther than 7 - 10m away and the scene is well illuminated. But for many this is an ideal situation which we don't have very often in real life.
Pentax 150-450mm provides much better solution for wildlife objects , but the maximum of 450mm focal length is often not long enough to obtain a large image with good details and contrast. The main object in such an image remains (even on a crop sensor !) too small , while intensive cropping and farther image modification leads to a low quality picture. This zoom with modern 1.4x convertor doesn't work well, providing low resolution images. Whether or not this is due to the fact , that 150-450mm is a full frame while the convertor is designed for crop sensor , I don't know. I tried four different convertors throughout the last 8 years of bird photography and all caused a considerable image quality deterioration . All, except for 1.4x-L full frame film era convertor.

Last edited by hatsofe; 06-14-2022 at 11:34 AM.
06-14-2022, 02:53 AM - 1 Like   #43
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QuoteOriginally posted by hatsofe Quote
I tried four different convertors throughout the last 8 years of bird photography and all caused a considerable image quality deterioration.
Did that include the HD Pentax-DA 1.4x AW AF Rear Converter?
I would be very interested to see your conclusions backed up by the test images which led to them.
06-14-2022, 03:48 AM   #44
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QuoteOriginally posted by Sandy Hancock Quote
Did that include the HD Pentax-DA 1.4x AW AF Rear Converter?
I would be very interested to see your conclusions backed up by the test images which led to them.
This image was made with 150-450mm only : Graceful Prinia | Hatsofe B | Flickr
This one was taken with 150-450mm +HD Pentax-DA 1.4x AW AF Rear Converter : White wagtail | Hatsofe B | Flickr
These are aproximately the same size objects , under bright sunlight and from a similar distance.
06-14-2022, 04:05 AM - 2 Likes   #45
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Fwiw.... I didn't rush in the get the DA 1.4TC..... but it finally got to the top of the list of "things I don't really need but somehow want". I can confirm that it pays not to overthink this type of purchase...... I did (as part of my due diligence) determine beforehand that world hunger was likely to be eradicated before Pentax released a FF TC.

I have since also discovered that the likely hood of needing the 1.4tc at any given time is inversly proportional to having it with you. Spookily... my memory is much the same nowdays.

Also.... I'm just as likely to use the 1.4 with say a K1 even though I have k3III.... life is to short to not mix things up a bit....

Last edited by noelpolar; 06-15-2022 at 04:13 AM.
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