Teleconverter or Gigapixel?

JimH123 said:

tomhongkong said:

That didn't seem to be the clearest way of showing the relative performances. I am trying again, with the actual size of the images (actually all cropped to equivalent of 2000x1500 to make it a bit more obvious)

I hope that makes more sense, otherwise please just ignore! Incidentally all settings on Gigapixel are at the lowest. I just find it does not do well where there are strong contrasts ad sharp edges like the lettering in these samples. It looks OK to me on the bricks

Based on these tests, I will continue to use the 1.4TC, and be very cautious of using GP to get a bigger magnification if I am hoping to print really large. I guess I will have to try to find a 2.0TC! (or stick with my 100-400)

Note, these were taken in atrocious conditions in RAW processed in DXO without any sharpening

toRAWI

Click to expand...

I have noticed this problem with lettering too. I suspect that the AI perhaps is not sufficiently trained on letterimg.

I need to do some experimenting with ON1 RAW Resize 2023, and see if it can do any better.

Click to expand...

I search though some old images to find something with text to compare text processing from Gigapixel AI at 2x vs ON1 RAW Resize 2023 at 2x. The sign was in one corner of the image and was cropped from 6000 x 4000 pixel to only 1309 x 1896 pixels, thus is quite a heavy crop. Gigapixel is on the left and ON1 Resize is on the right. And this is showing me that ON1 Resize, at least the 2023 version, is handling text better. I also have the 2019 version of ON1 Resize still on my PC as I have only loaded the 2023 version just a couple days ago with the Flack Friday sales.



The new size is now 2600 x 3769 pixels. On1 is clearly handling the text better. In fact, much better. I need to try more examples now as it has caught my attention.

Both conversions were done on the RAW file without using Lightroom. The camera was the Olympus EM5ii and the lens was the kit lens, the 14-42mm.

Here is an example of an extreme crop just to push Gigapixel AI and ON1 Resize just to see which one can do their best on an impossible task. Camera was an EM1 and the lens was an old Asahi Pentax Takumar 400mm f5.6 lens with an m42 mount.



And here is the side-by-side. Gigapixel on the left. ON1 Resize RAW 2023 version on the right.

JimH123 said:

I search though some old images to find something with text to compare text processing from Gigapixel AI at 2x vs ON1 RAW Resize 2023 at 2x. The sign was in one corner of the image and was cropped from 6000 x 4000 pixel to only 1309 x 1896 pixels, thus is quite a heavy crop. Gigapixel is on the left and ON1 Resize is on the right. And this is showing me that ON1 Resize, at least the 2023 version, is handling text better. I also have the 2019 version of ON1 Resize still on my PC as I have only loaded the 2023 version just a couple days ago with the Flack Friday sales.



The new size is now 2600 x 3769 pixels. On1 is clearly handling the text better. In fact, much better. I need to try more examples now as it has caught my attention.

Both conversions were done on the RAW file without using Lightroom. The camera was the Olympus EM5ii and the lens was the kit lens, the 14-42mm.

Click to expand...

Which model did you use for this in Gigapixel AI? Standard? Art & CG? Something else?

OMG, what people writing here about sensor size, amount of light or f-stop is just pure joy to read )))) ahaha, have not thought so many people have never attended school physics.

Teleconverter, or extender, is no more than just an enlarge. It magnifies image. Amount of light that gets into your lens is the same — as with TC or without. The difference is, that with image being magnified the intensity of light per square mm is being lower with TC than without it: same amount of light now spread over bigger area than before, e.g. “enlarged”, so overall luminosity over sensor area is lower with TC and that means you need to adjust your f-stop to get proper exposure.

Now — are TC useful or not? I suppose it depends on optical schema and acuity of lens + sensor system. If lens outperforms sensor initially, without TC, adding “enlarger” will not lead to lower acuity. If lens can not resolve all potential of sensor initially adding TC will just lead to same effect as enlarging final image in post — details are lost.
So, with big sensor with lower MP and good optical schema of lens TC will be better than digital enlargement. Think about Fujifilm GFX 50 MP Body and GF 250 lens. Lens outperforms body, so TC will work good.
Now think about different specter of things — high Megapixel body, e.g. 47 MP LUMIX S1r and average quality lens, say Sigma 100-400 DG DN. This lens is barely resolves 47 MP, so adding 1.4 TC will not make results better on this body. But at the same time, on 24 MP S1 that can be different!

Another factor is simply loose of small details over the distance — TC means you want to shoot far away from your target, but air pollution, light dispensary, thermal aberrations and other effects will lead to loose of details even if your optical schema is perfect.
That all factors lead to disappointment about TC’s: they work, but in limited field of conditions. But you also can think about them in a way that TC _can_ make better results but not in all situations, at the same time it will not be worse than digital enlargement. So you maybe not gain advantage always but you also do not loose anything with TC. When you evaluate any decision you need to think about alternative decisions: e.g. with my example of Sigma 100-400 spending 400 Euro on 1.4 TC will be suboptimal compare to investment same money in direction of Sigma 150-600 Sports lens.

I searched and found this recent thread about using a teleconverter and Topaz Photo AI.

faunagraphy said:

tomhongkong said:

OK, I am not necessarily advocating Gigapixel but it is pretty popular upsizing software. There are others.

However this is an interesting question. Assuming you had a 300f4 for example, and the bird image from 300mm is too small (low res) after cropping, are you better off using a TC or to upsize? Let's assume a 1.4xTC, the most commonly used size. (Bigger magnifications run into problems with both approaches)

The TC loses 1 stop of light. Gigapixel introduces artifacts as a result of upsizing (but not much with just a 1.4x upsize) Often I am balancing iso and shutter speed and 1 stop makes quite a difference.

Is 1 aperture stop loss worth the image degradation from upsizing.?... that's iso 1600 to 3200, or 3200 to 6400. DXO is getting pretty near the limit! How much does the 1.4x TC also introduce degradation? perceived wisdom is that the 2x TC does do so quite a lot.

What is your experience? Any samples?

Full disclosure: I am trying to decide if an MC14 is really an advantage on my 300, (or even an MC20!) or if I am better off doing it with software

tom

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I wrote a 'first impressions' review of Gigapixel last year. My conclusion was that it's a handy tool but cannot replace longer lenses (or TCs) because of the artefacts that it introduces into the image for unconventional textures (mud in case of my photos - it also made birds appear 'hairy' rather than 'feathered'). Ultimately, I decided to not purchase it.

https://www.dpreview.com/forums/post/64992345

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I'm not surprised. A TC throws the same image over more pixels so there is more real detail resolved, assuming tbe lens and TC are of sufficient quality. Gigapixel starts with the lens only image, up reses and applies AI guessing. It may or may not be more easing but it's less real. Reality may not bother some.

I am certainly willing to be proved wrong, but I was taught that the effect of a TC is to increase the focal length of a lens, acting like an additional lens group.

Since the focal length is greater and the objective remains the same, the combination has a higher (darker) 'F' number.

So a 300mm F4 with a 1.4 TC becomes a 420mm F5.6 requiring slower shutter speed

The image is not magnified and spread over more pixels (where do they come from?) but an image with a narrower field of view (appropriate to the longer FL) is projected on to the same sensor.

Resizing takes the original image and digitally increases the number of pixels. So with a 1.4 x resize our approx 5200x3900 image becomes 7300x 5400 pixels. If you crop the image to the original size the cropped portion of it is magnified.

Each technique has advantages. It appears that most resizing software introduces artifacts (more testing needed) however the original aperture remains (maybe useful in low light) and it may be easier to follow the subject (e.g BIF) when using the shorter real FL.and cropping later.

tom

tomhongkong said:

I am certainly willing to be proved wrong, but I was taught that the effect of a TC is to increase the focal length of a lens, acting like an additional lens group.

Since the focal length is greater and the objective remains the same, the combination has a higher (darker) 'F' number.

Click to expand...

it does not change focal length of a lens

tomhongkong said:

So a 300mm F4 with a 1.4 TC becomes a 420mm F5.6 requiring slower shutter speed

The image is not magnified and spread over more pixels (where do they come from?) but an image with a narrower field of view (appropriate to the longer FL) is projected on to the same sensor.

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That comes directly from manufacturers:

"A teleconverter is basically a magnifying lens that is placed between the camera body and lens."

"Teleconverters are convenient when you want to increase the apparent telephoto reach of specific NIKKOR lenses, especially when compared to the physical size of some of the longer super-telephoto NIKKORs. Also, when you use a teleconverter, you don’t lose the close focusing distance of the lens, which is an added benefit."

It does not change lens focal length. It makes an effect of "apparent telephoto reach", e.g. magnifies the picture to the field of view similar to one of a lens with different focal length.

https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/using-teleconverters.html

JimH123 said:

Here is an example of an extreme crop just to push Gigapixel AI and ON1 Resize just to see which one can do their best on an impossible task. Camera was an EM1 and the lens was an old Asahi Pentax Takumar 400mm f5.6 lens with an m42 mount.



And here is the side-by-side. Gigapixel on the left. ON1 Resize RAW 2023 version on the right.

Click to expand...

The ON1 Resize sample is not good. It's actually showing jaggies in the grass stems. Are you sure you've not done somthing wrong?

nameless0ne said:

tomhongkong said:

I am certainly willing to be proved wrong, but I was taught that the effect of a TC is to increase the focal length of a lens, acting like an additional lens group.

Since the focal length is greater and the objective remains the same, the combination has a higher (darker) 'F' number.

Click to expand...

it does not change focal length of a lens

nameless0ne said:

So a 300mm F4 with a 1.4 TC becomes a 420mm F5.6 requiring slower shutter speed

The image is not magnified and spread over more pixels (where do they come from?) but an image with a narrower field of view (appropriate to the longer FL) is projected on to the same sensor.

Click to expand...

That comes directly from manufacturers:

"A teleconverter is basically a magnifying lens that is placed between the camera body and lens."

Click to expand...

Exactly. That is the requirement of the additional element required to extend the focal length

nameless0ne said:

"Teleconverters are convenient when you want to increase the apparent telephoto reach

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That's a convennient way of explaining it

nameless0ne said:

of specific NIKKOR lenses, especially when compared to the physical size of some of the longer super-telephoto NIKKORs. Also, when you use a teleconverter, you don’t lose the close focusing distance of the lens, which is an added benefit."

It does not change lens focal length.

Click to expand...

It does not say that

nameless0ne said:

It makes an effect of "apparent telephoto reach", e.g. magnifies the picture to the field of view similar to one of a lens with different focal length.

https://www.nikonusa.com/en/learn-and-explore/a/tips-and-techniques/using-teleconverters.html

Click to expand...

I can only tell you what my professor explained at Uni.

tom

JimH123 said:

OutsideTheMatrix said:

Jim please try the TCON-17 on the 75-300 lens at 300mm and set the fnumber to f/9 as that is max resolution on that lens. Can you test that vs without any TC vs x2 DTC in camera and also the combo of the TC and the DTC together? From the reports I looked at, the TCON only helps for close subjects.

Click to expand...

OK, Here we go. All shots at f/9.

Here is a shot taken in RAW and converted to JPEG in LR with default settings



And a shot using the 2x DTC. SOOC with no adjustments.



And this time the RAW converted to JPEG with the TCON-17x



And now the DTC at 2x with the TCON-17x for a total magnification of 3.4x



Next, some comparisons:

RAW at 200% vs the DTC at 100%. No post-processing for either image. ISO was at 400.


RAW at 200% vs the DTC at 100%

This time, used GPAI at 2x on the RAW (thru Lightroom) and the 2x DTC on the right.


GPAI at 2x on the RAW (thru Lightroom) and the 2x DTC

This time, the image on the left is the original RAW with GPAI at 3.4x and on the right is the DTC and the TCON-17x


original RAW with GPAI at 3.4x and on the right is the DTC and the TCON-17x

Changing the left image to RAW with TCON and right DTC with TCON


RAW with TCON and right DTC with TCON

One conclusion I can draw from this is the 2X DTC is better than I had been expecting.

Also, the TCON-17x is better than expected too.

Click to expand...

Yes they both are pretty good! Would you rank 2x DTC higher or TCON-17 higher? I think using the TCON-17 is best. What was the focusing distance, do you remember? And how do they compare to Gigapixel? Also what is needed to attach the TCON-17 to this lens? And how does the "stack" of TCON-17 on top of the 2x DTC fare? Is 3.4x really possible with this lens with any kind of good image quality? Better than 3.4x Gigapixel?

Is that last image also a 3.4x vs 3.4x comparison just like the one above it?

My interpretation is that 1.7x and 2x are both very good and better than the software rendition, but that 3.4x is better with the software.

It would be interesting to see a head to head comparison of the 1.7x TC vs the 2x DTC!

--
In the councils of government, we must guard against the acquisition of unwarranted influence, whether sought or unsought, by the military industrial complex. The potential for the disastrous rise of misplaced power exists and will persist. We must never let the weight of this combination endanger our liberties or democratic processes. We should take nothing for granted. Only an alert and knowledgeable citizenry can compel the proper meshing of the huge industrial and military machinery of defense with our peaceful methods and goals, so that security and liberty may prosper together.
-Dwight D. Eisenhower, 1961

zotynimon said:

JimH123 said:

I search though some old images to find something with text to compare text processing from Gigapixel AI at 2x vs ON1 RAW Resize 2023 at 2x. The sign was in one corner of the image and was cropped from 6000 x 4000 pixel to only 1309 x 1896 pixels, thus is quite a heavy crop. Gigapixel is on the left and ON1 Resize is on the right. And this is showing me that ON1 Resize, at least the 2023 version, is handling text better. I also have the 2019 version of ON1 Resize still on my PC as I have only loaded the 2023 version just a couple days ago with the Flack Friday sales.



The new size is now 2600 x 3769 pixels. On1 is clearly handling the text better. In fact, much better. I need to try more examples now as it has caught my attention.

Both conversions were done on the RAW file without using Lightroom. The camera was the Olympus EM5ii and the lens was the kit lens, the 14-42mm.

Click to expand...

Which model did you use for this in Gigapixel AI? Standard? Art & CG? Something else?

Click to expand...

I used standard for this one. I intend to run it again with several more modes.

Tumulous said:

JimH123 said:

Here is an example of an extreme crop just to push Gigapixel AI and ON1 Resize just to see which one can do their best on an impossible task. Camera was an EM1 and the lens was an old Asahi Pentax Takumar 400mm f5.6 lens with an m42 mount.

And here is the side-by-side. Gigapixel on the left. ON1 Resize RAW 2023 version on the right.

Click to expand...

The ON1 Resize sample is not good. It's actually showing jaggies in the grass stems. Are you sure you've not done somthing wrong?

Click to expand...

I did do something wrong. Now one difference is the ON1 Resize does not take care of noise and it has to be treated separately, whereas Gigapixel AI has a noise slider to deal with the noise. In the following examples, I will use 3 different Gigapixel AI models and mention what I had to set the noise slider to clean up the noise. But in the case of ON1 Resize, I started with DxO Photolab to deal with the noise and then followed that with ON1 Resize.

By far, the ON1 Resize was the worst rendition. Interesting how well it did on lettering in previous reply, but in this case, not so good. Of course, this is an extreme example.




GPAI Std Model 4x Noise Slider = 43


GPAI Low Res Model 4x Noise Slider = 10


GPAI Very Compressed Model 4x Noise Slider = 2


Started with RAW file in DxO PL 6 and used Deep Prime XD, then ON1 Resize RAW 2023 4x

OutsideTheMatrix said:

JimH123 said:

OutsideTheMatrix said:

Jim please try the TCON-17 on the 75-300 lens at 300mm and set the fnumber to f/9 as that is max resolution on that lens. Can you test that vs without any TC vs x2 DTC in camera and also the combo of the TC and the DTC together? From the reports I looked at, the TCON only helps for close subjects.

Click to expand...

OK, Here we go. All shots at f/9.

Here is a shot taken in RAW and converted to JPEG in LR with default settings. No magnification.



And a shot using the 2x DTC. SOOC with no adjustments. Magnification = 2.0x.



And this time the RAW converted to JPEG with the TCON-17x. Magnification is now 1.7x.



And now the DTC at 2x with the TCON-17x for a total magnification of 3.4x



Next, some comparisons:

RAW at 200% vs the DTC at 100%. No post-processing for either image. ISO was at 400. I would say the DTC is better.


RAW at 200% vs the DTC at 100%

This time used GPAI at 2x on the RAW (thru Lightroom) and the 2x DTC on the right. They are closer, but perhaps the DTC is a little better.


GPAI at 2x on the RAW (thru Lightroom) and the 2x DTC

This time, the image on the left is the original RAW with GPAI at 3.4x and on the right is the DTC for 2.0x and the TCON-17x for 1.7 and combined they are at 3.4x


original RAW with GPAI at 3.4x and on the right is the DTC and the TCON-17x

Changing the left image to RAW with TCON at 1.7x and right DTC with TCON at 1.7x. The results are very close.


RAW with TCON and right DTC with TCON

One conclusion I can draw from this is the 2X DTC is better than I had been expecting.

Also, the TCON-17x is better than expected too.

Click to expand...

Yes they both are pretty good! Would you rank 2x DTC higher or TCON-17 higher?I think using the TCON-17 is best.

Click to expand...

I haven't reached a conclusion on this yet. Have to be satisfied with JPEG only to use 2x DTC vs continuing with 16 bit results when using the TCON-17x.

OutsideTheMatrix said:

What was the focusing distance, do you remember?

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The distance was 45-50 feet to the top of the tree. I used a tripod and release shutter release.

OutsideTheMatrix said:

And how do they compare to Gigapixel?

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More examples needed.

OutsideTheMatrix said:

Also what is needed to attach the TCON-17 to this lens? And how does the "stack" of TCON-17 on top of the 2x DTC fare?

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All it takes with the 75-300mm lens was to use a 58mm to 55mm step down ring and to then just screw the back end of the TCON-17x into the step down ring. But it is sure a lot of mass out on the end of the lens. I don't use it for anything except demonstrating how it works.

OutsideTheMatrix said:

Is 3.4x really possible with this lens with any kind of good image quality? Better than 3.4x Gigapixel?

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This would be the next to last example. Zoom in and compare.

OutsideTheMatrix said:

Is that last image also a 3.4x vs 3.4x comparison just like the one above it?

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No, the last is 1.7x vs 1.7x.

OutsideTheMatrix said:

My interpretation is that 1.7x and 2x are both very good and better than the software rendition, but that 3.4x is better with the software.

It would be interesting to see a head to head comparison of the 1.7x TC vs the 2x DTC!

Click to expand...

I can do this later. Have to go somewhere right now.

tomhongkong said:

I am certainly willing to be proved wrong, but I was taught that the effect of a TC is to increase the focal length of a lens, acting like an additional lens group.

Click to expand...

Actually, the TC spreads out the light so that the sensor only sees the central part of the image. The effect is that the image will look magnified. And the light density goes down due to the light being spread out making the image as seen by the sensor darker.

The opposite effect comes from a speed booster such as one by Metabones. In this case, the cone of light from the lens is concentrated such that area outside of what the sensor would normally use is brought onto the sensor making the FOV appear wider. Of course, this will only work when using a lens with a wide cone of light than what the sensor actually uses such as full frame lens on crop sensor camera.

tomhongkong said:

Since the focal length is greater and the objective remains the same, the combination has a higher (darker) 'F' number.

So a 300mm F4 with a 1.4 TC becomes a 420mm F5.6 requiring slower shutter speed

The image is not magnified and spread over more pixels (where do they come from?) but an image with a narrower field of view (appropriate to the longer FL) is projected on to the same sensor.

Resizing takes the original image and digitally increases the number of pixels. So with a 1.4 x resize our approx 5200x3900 image becomes 7300x 5400 pixels. If you crop the image to the original size the cropped portion of it is magnified.

Each technique has advantages. It appears that most resizing software introduces artifacts (more testing needed) however the original aperture remains (maybe useful in low light) and it may be easier to follow the subject (e.g BIF) when using the shorter real FL.and cropping later.

tom

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In reply to Tomhongkong:

JimH123 said:

tomhongkong said:

I am certainly willing to be proved wrong, but I was taught that the effect of a TC is to increase the focal length of a lens, acting like an additional lens group.

Click to expand...

Actually, the TC spreads out the light so that the sensor only sees the central part of the image. The effect is that the image will look magnified. And the light density goes down due to the light being spread out making the image as seen by the sensor darker.

Click to expand...

Correct. And that means that the magnified image benefits from the full sensor resolution and contains additional real image information. Provided the lens/TC combination still out-resolves the sensor. Which is only the case if both the lens and the TC are of exceptionally high quality.

JimH123 said:

The opposite effect comes from a speed booster such as one by Metabones. In this case, the cone of light from the lens is concentrated such that area outside of what the sensor would normally use is brought onto the sensor making the FOV appear wider. Of course, this will only work when using a lens with a wide cone of light than what the sensor actually uses such as full frame lens on crop sensor camera.

JimH123 said:

Since the focal length is greater and the objective remains the same, the combination has a higher (darker) 'F' number.

So a 300mm F4 with a 1.4 TC becomes a 420mm F5.6 requiring slower shutter speed

The image is not magnified and spread over more pixels (where do they come from?) but an image with a narrower field of view (appropriate to the longer FL) is projected on to the same sensor.

Resizing takes the original image and digitally increases the number of pixels.

Click to expand...

Click to expand...

Correct.

JimH123 said:

JimH123 said:

So with a 1.4 x resize our approx 5200x3900 image becomes 7300x 5400 pixels.

Click to expand...

Click to expand...

Correct. But unlike when using a TC, the up-sized image does NOT contain more real image information. It instead contains new, artificially created fake information that does not exist in the original scene. These are digital artifacts. Some may please your eye, some may not, but they are all artifacts nonetheless.

Similar to artificial bokeh that some phones create. If you are fine with that, you will be fine with Gigapixel too. You see, PP software like Gigapixel is not exclusively made for owners of dedicated photography gear. Phone owners increasingly use such PP software packages too. And phone makers use similar AI technologies to increase the apparent FL of their size limited tele lenses. It all depends what you want to use the resulting pictures for.

You get what you pay for. If you want high IQ extreme tele pictures, then you have to pay for sharp lenses and TC's. There is no cheap shortcut.



Digital artifact in information science, is any undesired or unintended alteration in data introduced in a digital process by an involved technique and/or technology.

JimH123 said:

JimH123 said:

If you crop the image to the original size the cropped portion of it is magnified.

Each technique has advantages. It appears that most resizing software introduces artifacts (more testing needed) however the original aperture remains (maybe useful in low light) and it may be easier to follow the subject (e.g BIF) when using the shorter real FL.and cropping later.

tom

Click to expand...

Click to expand...

JimH123 said:

OutsideTheMatrix said:

My interpretation is that 1.7x and 2x are both very good and better than the software rendition, but that 3.4x is better with the software.

It would be interesting to see a head to head comparison of the 1.7x TC vs the 2x DTC!

Click to expand...

I can do this later. Have to go somewhere right now.

Click to expand...

Here is the comparison.

First image is a resize from Lightroom using Gigapixel AI at 1.7x using the Low Res Model. No other adjustments have been made.



And here is the Digital TC at 2.0x. No adjustment made to the file.



Next, a side-by-side, zoomed in for a closer look. GPAI 1.7x on left. DTC 2.0x on right.



From what I see, the GPAI is far better than the DTC. I see the DTC is not quite as sharp and I see some CA on the small twigs that I don't see on the GPAI version.

Plus, the GPAI is not a JPEG and more processing is still available.

***********************************************************

Adding image with TCON-17x



And here is the side-by-side comparison. TCON-17x on the left, DTC 2.0 on the right.





My conclusion is that the image using the TCON-17x is superior to DTC at 2.0x.

tomhongkong said:

tomhongkong said:

I can only tell you what my professor explained at Uni.

Click to expand...

tom

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I think this is what's called the "credentials fallacy" argument.

BobT3218 said:

tomhongkong said:

Bobapingu said:

I can only tell you what my professor explained at Uni.

Click to expand...

tom

Click to expand...

I think this is what's called the "credentials fallacy" argument.

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A pretty snide comment without any justification

You could always add the explanations from many google searches (which I have just done to try to arive at the truth of this matter) which say that the focal length is extended (supporting my professor's view) To take one such article from 'the ultimate guide to tele extenders'

"The third reason you might want to use an extender is to get to a focal length that’s not available natively in any other lens. If you used a 600mm lens with a 2x extender, you would have a 1200mm reach, something that’s not possible to achieve any other way. Even a 600mm with a 1.4x extender gets you to 840mm which is a little longer than an 800mm prime (the longest lens being made at the time of writing this article, apart from highly specialist limited manufacture lenses).

So to summarize the advantages, an extender gives you:

• A longer focal length (obviously) {my bold}
• A better focal length/weight ratio
• A better focal length/price ratio (there are some exceptions)
• Double the compositional options
• A way to get to focal lengths that aren’t achievable with a prime lens on its own"

It does go on to say

"Simplistically speaking, an extender is just like a magnifying glass that enlarges the central portion of your lens’ field of view and projects that onto the camera’s sensor. (my bold). Since it’s only projecting a smaller central part of the original lens, vignetting is actually reduced when using an extender. Unfortunately, all of the flaws in the original lens become magnified so this means that chromatic aberrations become more apparent, the image becomes softer and there is a reduction in contrast. A 2x extender will therefore always deliver a softer image because it is magnifying the flaws by 2x instead of 1.4x. The actual optical quality of the extender itself doesn’t have as big a part to play in this whole thing as most people would imagine. It’s the original lens’ optical quality that pays a huge part! If the lens didn’t have any flaws then there would be none to magnify, right?"

Many other articles say that the focal length is extended....just look them up!

I guess the perpetuation of this simplistic view is what causes the confusion.

It is all pretty academic and irrelevant in terms of the original question, which attempted to compare the results from TCs or AI resizers (of various flavours) and which some responders have given useful answers. Thank you to them.

tom

tomhongkong said:

BobT3218 said:

tomhongkong said:

tomhongkong said:

I can only tell you what my professor explained at Uni.

Click to expand...

tom

Click to expand...

I think this is what's called the "credentials fallacy" argument.

Click to expand...

A pretty snide comment without any justification

You could always add the explanations from many google searches (which I have just done to try to arive at the truth of this matter) which say that the focal length is extended (supporting my professor's view) To take one such article from 'the ultimate guide to tele extenders'

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I hope your professor done her job well. I just don‘t understand this argument about university so I have ignored it. I have two university degrees myself — in math and economics but I don‘t write about that at every corner so was funny to see your statement )))

tomhongkong said:

"The third reason you might want to use an extender is to get to a focal length that’s not available natively in any other lens. If you used a 600mm lens with a 2x extender, you would have a 1200mm reach, something that’s not possible to achieve any other way. Even a 600mm with a 1.4x extender gets you to 840mm which is a little longer than an 800mm prime (the longest lens being made at the time of writing this article, apart from highly specialist limited manufacture lenses).

So to summarize the advantages, an extender gives you:

• A longer focal length (obviously) {my bold}
• A better focal length/weight ratio
• A better focal length/price ratio (there are some exceptions)
• Double the compositional options
• A way to get to focal lengths that aren’t achievable with a prime lens on its own"

It does go on to say

"Simplistically speaking, an extender is just like a magnifying glass that enlarges the central portion of your lens’ field of view and projects that onto the camera’s sensor. (my bold). Since it’s only projecting a smaller central part of the original lens, vignetting is actually reduced when using an extender. Unfortunately, all of the flaws in the original lens become magnified so this means that chromatic aberrations become more apparent, the image becomes softer and there is a reduction in contrast. A 2x extender will therefore always deliver a softer image because it is magnifying the flaws by 2x instead of 1.4x. The actual optical quality of the extender itself doesn’t have as big a part to play in this whole thing as most people would imagine. It’s the original lens’ optical quality that pays a huge part! If the lens didn’t have any flaws then there would be none to magnify, right?"

Many other articles say that the focal length is extended....just look them up!

I guess the perpetuation of this simplistic view is what causes the confusion.

It is all pretty academic and irrelevant in terms of the original question, which attempted to compare the results from TCs or AI resizers (of various flavours) and which some responders have given useful answers. Thank you to them.

tom

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extender does not change a focal length of a lens, sorry. It the same as using 300 mm lens on a camera with a crop factor 2.0 does not change focal length of a lens.
Extender magnifies a central part of an image that lens produces to fill a bigger area of a full sensor, leading to the effect similar to the use of a lens with bigger focal length. But it‘s important to understand that it does not change focal length of a lens, so magnification effect does not add more details to the image and lead to loose of light intensity. So sorry, it’s just magnification with all it drawbacks.