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Comparison of teleconverters & barlows (1 Viewer)

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Paul Corfield

Well-known member
Did a comparison of all my different types of magnification today. As a good test I used a bank note for it's extra fine detail.

The first row of photos are at the lower end, all 1.5X and under. The second row of photos are all 2X and above. Information is on the photos.

These are all 100% crops from around 8m (26 feet) range. All were focused using Live View to get as close as possible to perfect focus. All are unedited apart from a slight levels adjustment to make them as similar as possible.

At the lower end I'd say it's pretty close between the Kenko 1.4X and the Antares 1.5X, but around £75 difference in price.

At the higher end the 2" Antares 1.6X (giving 2.3X on the scope) is the clear winner.

Paul.
 

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Did a direct comparison of the GSO 2X ED and Antares 1.6X barlows. This time I put a 70mm macro tube between the GSO and the camera and this brings it up to around the same magnification as the Antares.

The photos are very hard to split but on closer inspection the Antares has resolved the details a little better than the GSO. Look at the pupils especially and you can see more detail in the Antares one. The black lines are slightly finer too on the Antares version where as the GSO ones are slightly fatter.

There's very little in it though and both do an excellent job.

Paul.
 

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Agreed - even with my rediculous eyesight, the Ant is the slightly better of the 2, but i bet you wouldnt notice this in normal everyday cropping
 
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That's right, air quality and too much heat shimmer will likely degrade the image before you notice any loss in quality from the optics. With 2" barlows being generally limited to the GSO and Antares then either of them are a good choice depending on your budget. The GSO stacks up well with the Antares too and I'll post an example soon.

Paul.
 
Here's a comparison of the Antares 1.6X stacked with a Kenko Pro 1.4X TC and then the Antares stacked with a GSO 2X ED barlow. Slightly more magnification with the two stacked barlows but slightly better image quality with the Kenko.

Also for those that don't have access to British bank notes, the iris part of the eye that I'm photographing is only 2.5mm across and the pupil just under 1mm. Range is 7m and all the posted images are 100% crops.

Paul.
 

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Thanks Paul for your excellent work.

¿Could you share an Image without magnification, only telescope??

How has you stacked the barlow + the TC??? If I put the kenko, I can´t put the barlow near sensor...

Thanks you and sorry my english...
 
Here's the bank note at 600mm without cropping and also one showing 100% crop from the 600mm. I've also posted a photo showing how I would attach the Kenko TC and the barlow together. With the Antares it's not possible to have it close to the camera. You could strip it down, remove the element and then try and remount it but I think it's a little too expensive to go doing that. I have removed the element just to have a look but it's a few mm bigger than the GSO and I haven't found anything to mount it in easily. It works fine as it is so there's no real need to alter it.

Paul.
 

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The Antares will be similar to the Kenko 2X, probably a little better but it does take perfect conditions to see the difference. It's generally very early morning or late afternoon when I see the extra sharpness, when the heat of the sun isn't interfering with the quality of the air. Mornings and afternoons the sun just ruins everything at this time of year, especially here anyway.

What don't you like about the Ultima?

Paul.
 
I only tested the celestrom 2 days and i don't like results... i´ll try to test it again and i show you the photos, but not good sharpen and sometimes a light white in the middle.

Regards.
 
The celestron ultima needs to be baffled on the front. Easiest way is to get some black card and make a circle the same size diameter as the barlow glass. Then cut a hole about 1cm diameter in the middle of the cardboard disc and stick the cardboard disc to the front of the barlow with blu-tac or something similar. This will greatly improve the contrast of the photos and also remove the problem of the white bit in the middle of the photo. For sharpness always use a shutter release cable as the barlow increase magnification quite a bit.

Paul.
 
Thank you for doing this comparison, Paul. I can see that barlows are as good or better than teleconverters in center sharpness. This does make sense... teleconverters are heavily restricted in terms of where they have to be in the light path, whereas barlows can be much deeper into it.

Could you please extend this comparison to show 100% crops from the corners?
Corner sharpness is important to me; I like the freedom to compose my subject in the corner without worrying about reduced sharpness.

With my two Canon 2x II and one Canon 1.4x II all stacked together for 5.53x magnification, there's a whole lot of chromatic aberration in the corners, and I'm wondering if a single high-power barlow would do a better job. (The two 2x's stacked for 3.97x also yield very noticeable CA.)
 
David Ellsworth said:
Could you please extend this comparison to show 100% crops from the corners?
Corner sharpness is important to me; I like the freedom to compose my subject in the corner without worrying about reduced sharpness.
Click to expand...

Done a test for you David, see this post and the next 2.

First is just the scope. A photo through the scope showing the test chart I downloaded. 2nd image is 100% crop of the centre and 3rd is 100% crop of bottom right corner. Scope shows hardly any CA and still pretty sharp in the corner.


Paul.
 

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These two photos are taken using my 2" Antares 1.6X barlow. In reality the barlow gives 2.3X when used in combination with a dslr and scope. This increase in mag is down to the distance from the barlow to the film sensor.

A little bit of CA in the corner and slightly softer but not much.

Paul.
 

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These two are taken with the Kenko Pro 300 1.4X teleconverter. A tiny bit of CA but stays sharp all the way to the corners.

Paul.
 

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Paul, thanks, but I think that is a rather bad target pattern for a chromatic aberration test. Much of the chromatic aberration that would be seen would be radial, and would be hidden along those radial lines.

Could you please do the test with money, like you did in the thread-starter? Or some other target with lots of fine detail of lines at all angles, not strictly constricted angles. (Actually, I was thinking you could use the originals from the test you did on 7 May.)

Do you still have the 1.5x apochromatic barlow? I am especially interested in the difference between an apochromatic barlow and an achromat of similar or equal power (when also compared with a DSLR teleconverter).
 
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I'd deleted all the old photos of the money but I re-done them this morning, shall post later. The Antares 1.5X Apro barlow was quite soft in the corners I noted so that probably wont be any good. Second softest in the corners was the 2" GSO barlow. Kenko 1.4X TC and the Antares 2.3X were both quite sharp in the corners.

If money was no object I'd probably get a flat field barlow I saw the other day. It's a Zeiss designed Baader Fluorite Flatfield Barlow which cost around $735. It uses true CaF2 fluorite glass in all elements and is supposed to be sharper than any barlow or converter in existence. Gives variable mag from 3X to 8X. Hefty price tag though.

Paul.
 
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