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New 840mm lens?

  
 
AGeoJO
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p.1 #1 · p.1 #1 · New 840mm lens?


Well, sort of... but not really. The sharpness of the new GM 300mm is truly remarkable. Often times we see how well this lens performs combined with a 2X TC. I am trying to push a little bit further by stacking two Sony TCs on this lens. Back then in the "C" days, I tried stacking 2 TCs but the effort resulted in a "meh" outcome. Plus, the AF didn't work and focusing the combo manually was not that easy.

You do need an extension tube to enable you to stack the 2 TCs. I have 2 sets of an extension tubes. The first one was a cheapo Fotga but the shorter extension tube, the one I more so, had a connection issue that developed later. I bought a sturdier extension tube set and still use that until now for close-up photography. The baffle of the Fotga extension tube is round. So, when I lost the tall lens cap for one of my Sony TCs,, I ended up using the long Fotga extension tube that allows me to use a regular cap. As it turns out the Fotga is just perfect for the purpose of TCs stacking.

Some other extension tubes, like Kenko or Meike, have rectangular inner baffles that prevents the thick, rounded protective rubber around the optical elements of the TC to go in. I know some folks have shaven off/remove the baffle, which can be done easily since the baffle is made out of soft foam material. The inner section though has to be painted using mate paint to minimize reflection.

The 1.4X TC has to be mounted first, then the extension tube and then the 2X TC before the lens. Only the 1.4X TC is reported. So, all the images taken using this setup will appear to have been taken only with the 1.4X TC. But it is actually 1.4 X 2 X whatever focal length and in the case of the GM 300mm the effective focal length is 840mm. To my pleasant surprise, the AF works great and quite snappy on the A1. The Eye-AF works, too. What's the drawback of this setup? Besides the obvious effective aperture of being f/8, which is pretty slow but acceptable, this stacked TCs won't let you focus to infinity. Depending on the lens used, the 300mm here lets you focus to about 80 feet or so, which is not bad at all. You can focus closer than the minimum focusing distance indicates though.

How is the optical performance? To my surprise, it is actually quite good. I first tried the combo in my backyard but flowers, leaves or whatnot are not that good for this evaluation. I took the setup to a local falcon site yesterday but the falcon was not cooperating. So, I ended up targeting some ground squirrels that were roaming around. Will I be using this setup for real-life conditions? If this lens is the only lens I have available and the 2X TC doesn't give me enough reach, AND the distance to the target is about less than 80 feet or so, then I would. Can I crop the file later to get the magnification I need without resorting to the combo? Sure! But I ended up with less MP of the file. Here, I still keep the full resolution at 50 MP. And using the same principle of cropping or shooting in APS-C, I can even crop it further, too. However, you need to keep in mind that you loose your infinity focus with this setup. I could see the falcon chicks in the nest from far away but I couldn't get them in focus with this setup. Regardless for anything closer, I was pleasantly surprised with how this combo works.

Yes, I do have longer lenses and would resort to any of them under regular circumstances. But it was fun trying to experiment what we can get away with... BTW, all images were processed using LR only and some were processed using the AI Denoise in LR.

Thank you for looking!



AGeoJO 2024

The effective focal length is really 840mm and not what it indicates here.

  ILCE-1    FE 300mm F2.8 GM OSS + 1.4X Teleconverter lens    420mm    f/4.0    1/1000s    4000 ISO    0.0 EV  





AGeoJO 2024

Crop from above

  ILCE-1    FE 300mm F2.8 GM OSS + 1.4X Teleconverter lens    420mm    f/4.0    1/1000s    4000 ISO    0.0 EV  





AGeoJO 2024

840mm

  ILCE-1    FE 300mm F2.8 GM OSS + 1.4X Teleconverter lens    420mm    f/4.0    1/1000s    3200 ISO    0.0 EV  





AGeoJO 2024

840mm

  ILCE-1    FE 300mm F2.8 GM OSS + 1.4X Teleconverter lens    420mm    f/4.0    1/2000s    6400 ISO    0.0 EV  





AGeoJO 2024

840mm

  ILCE-1    FE 300mm F2.8 GM OSS + 1.4X Teleconverter lens    420mm    f/4.0    1/2000s    6400 ISO    0.0 EV  





AGeoJO 2024

Just with 2X and yes, it is better

  ILCE-1    FE 300mm F2.8 GM OSS + 2X Teleconverter lens    600mm    f/5.6    1/1000s    640 ISO    0.0 EV  





AGeoJO 2024

The combo mounted on A1





AGeoJO 2024

Rounded inner baffle of Fotga extension tube





AGeoJO 2024

Fotga extension tube mounted on A1




Jun 10, 2024 at 09:31 PM
freaklikeme
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p.1 #2 · p.1 #2 · New 840mm lens?


Thanks for sharing, Joshua. I wouldn't have even thought of this. I'll have to pick up one of those tubes and give it a try.


Jun 10, 2024 at 09:53 PM
arbitrage
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p.1 #3 · p.1 #3 · New 840mm lens?


I tried this last weekend with my friend's lens. But found the limitation to the focus distance to be a bit of an issue. I recall when I stacked on the 600GM you could focus way out and just couldn't go all the way to infinity. With the 300GM the distance was much more restricting and I think I'd miss shots when things happen outside that focal range.


Jun 10, 2024 at 10:21 PM
AGeoJO
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p.1 #4 · p.1 #4 · New 840mm lens?


freaklikeme wrote:
Thanks for sharing, Joshua. I wouldn't have even thought of this. I'll have to pick up one of those tubes and give it a try.


Thank you, Brad! I don't remember how much I paid the Fotga for since it was quite a while already but I believe it was less than $20. Worthwhile trying that "trick".



Jun 10, 2024 at 10:28 PM
AGeoJO
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p.1 #5 · p.1 #5 · New 840mm lens?


arbitrage wrote:
I tried this last weekend with my friend's lens. But found the limitation to the focus distance to be a bit of an issue. I recall when I stacked on the 600GM you could focus way out and just couldn't go all the way to infinity. With the 300GM the distance was much more restricting and I think I'd miss shots when things happen outside that focal range.


Geoff, the shorter the focal length, the shorter the infinity focus limitation becomes apparent. Yes, with the 600mm you can almost get away with almost to infinity. I tried that a few years back at the owl site. Alex Phan was there, among others. Based on my estimation, you can focus to 70-80 feet. I would not use the setup for any BIF. Squirrels running around, yes 😎. I am planning of using this lens as my longest lens on a trip and since it is not a strictly a bird photography trip at that, I am limited in what I want to take with me I got the hunch that I will be using the TC quite a bit and as the last resort, I will use the stacked TCs. Thanks for commenting!



Jun 10, 2024 at 10:41 PM
Slalom
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p.1 #6 · p.1 #6 · New 840mm lens?


I believe that the extension tube is reducing the focus range, not sure if the tc's increase the effect.

So the smallest extension is best.



Jun 11, 2024 at 03:02 AM
deevee
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p.1 #7 · p.1 #7 · New 840mm lens?


Hmm... I"ve tried this before using the 16mm Fotga and AF wouldn't work ...Not sure what I did wrong ... I may have to try again then ... Thanks for the report


Jun 11, 2024 at 08:19 AM
AGeoJO
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p.1 #8 · p.1 #8 · New 840mm lens?


Slalom wrote:
I believe that the extension tube is reducing the focus range, not sure if the tc's increase the effect.

So the smallest extension is best.


Extension tubes do change the focusing ability of the lens alright. Because the distance between the sensor and optics increases by the thickness of the extension tube/tubes, the setup looses the ability to focus to infinity. Yes, a thinner extension tube indeed would minimize the effect of loosing infinity focus but physically, it is not enough to allow the subsequent TC, the 2X TC, in this case, to be mounted.



Jun 11, 2024 at 09:13 AM
AGeoJO
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p.1 #9 · p.1 #9 · New 840mm lens?


deevee wrote:
Hmm... I"ve tried this before using the 16mm Fotga and AF wouldn't work ...Not sure what I did wrong ... I may have to try again then ... Thanks for the report


Thanks, DV! The Fotga extension tube is finicky and to my pleasant surprise it works well for me. Give it another shot later, please and clean the contacts on both end beforehand.



Jun 11, 2024 at 09:16 AM
freaklikeme
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p.1 #10 · p.1 #10 · New 840mm lens?


The extension tubes are $27.99 from the Fotoga store on Amazon. You can get them cheaper on the bay directly from China.

I thought maybe if you reversed the position of the converters (2x on the camera side, 1.4x on the lens) you might be able to get away with the 10mm tube but, after measuring the extension of the 2x, I don't think it'll work.



Jun 11, 2024 at 07:53 PM
 


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AGeoJO
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p.1 #11 · p.1 #11 · New 840mm lens?


freaklikeme wrote:
The extension tubes are $27.99 from the Fotoga store on Amazon. You can get them cheaper on the bay directly from China.

I thought maybe if you reversed the position of the converters (2x on the camera side, 1.4x on the lens) you might be able to get away with the 10mm tube but, after measuring the extension of the 2x, I don't think it'll work.


I don't remember how much I paid for mine. Probably, it was more like $15. For sure, I know it was less than $20 some 10 years ago

Back then during "C" days, you had to mount the 1.4X and then the 2X due to some physical limitations,. I carried that sequence over to this side. But as it turns out with Sony TCs, the sequence of mounting doesn't matter. The 16mm tube is thick enough to accommodate both mounting sequences. And yes, the 10mm is too thin for this...



Jun 11, 2024 at 08:59 PM
Choderboy
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p.1 #12 · p.1 #12 · New 840mm lens?


If 12mm was long enough, you may not, in practicle terms, lose infinity focus.
With Canon stacking, there was a little loss of infinity, but I could still focus on the moon.
I don't know of any 12mm tubes, probably easy with a lathe to make one from a 16.



Jun 11, 2024 at 09:23 PM
freaklikeme
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p.1 #13 · p.1 #13 · New 840mm lens?


AGeoJO wrote:
I don't remember how much I paid for mine. Probably, it was more like $15. For sure, I know it was less than $20 some 10 years ago

Back then during "C" days, you had to mount the 1.4X and then the 2X due to some physical limitations,. I carried that sequence over to this side. But as it turns out with Sony TCs, the sequence of mounting doesn't matter. The 16mm tube is thick enough to accommodate both mounting sequences. And yes, the 10mm is too thin for this...


Everything's more expensive now, but $28 bucks is worth it to me to give it a try. Unfortunately, they still ship from China, so it'll be a while before I receive them.

My "C" days was what made me give up on stacking. I never got the results you're getting here, so it left my thinking. And I'm not sure how much I'll use it, but I've got a couple of resident river otters for whom it could be the perfect solution.

---------------------------------------------

Choderboy wrote:
If 12mm was long enough, you may not, in practicle terms, lose infinity focus.
With Canon stacking, there was a little loss of infinity, but I could still focus on the moon.
I don't know of any 12mm tubes, probably easy with a lathe to make one from a 16.


Sounds like a business opportunity to make and sell one that's the perfect length. As popular as the 300's apparently been for Sony, it would probably make for nice boutique side gig.

Edited on Jun 11, 2024 at 10:24 PM · View previous versions



Jun 11, 2024 at 09:51 PM
AGeoJO
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p.1 #14 · p.1 #14 · New 840mm lens?


Choderboy wrote:
If 12mm was long enough, you may not, in practicle terms, lose infinity focus.
With Canon stacking, there was a little loss of infinity, but I could still focus on the moon.
I don't know of any 12mm tubes, probably easy with a lathe to make one from a 16.


The longer the focal length of the lens the less the effect of losing infinity focus. In this case, a 300mm lens is the target for this TC stacking effort. With this lens, it seems the limit is about 80 feet or some 25m. That distance is fine for my usage, especially if this is the only lens I have on the trip I am planning. For anything else, I can use either one of the other GM long lenses to get more reach.

We still want to get the AF and the exif data, although the effective aperture and FL data is no longer correct but the ISO setting is. As such, we don't want to loose the electronic contacts provided by the TC if you butcher the 16mm extension tube.



Jun 11, 2024 at 09:58 PM
Magnum PI
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p.1 #15 · p.1 #15 · New 840mm lens?


You are doing it wrong. Get some nuts - no need for 800m.


Jun 11, 2024 at 10:45 PM
freaklikeme
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p.1 #16 · p.1 #16 · New 840mm lens?


In my experience, feeding squirrels is the fastest way to acquire lifelong (their lives, anyway) overly chatty tormentors.

All you really need is a backyard with a ton of trees. They're my favorite manual focus practice targets.

BudMuncher by Bradley Clemens, on Flickr

Squirrel@171mm by Bradley Clemens, on Flickr



Jun 12, 2024 at 03:33 AM
Choderboy
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p.1 #17 · p.1 #17 · New 840mm lens?


AGeoJO wrote:
The longer the focal length of the lens the less the effect of losing infinity focus. In this case, a 300mm lens is the target for this TC stacking effort. With this lens, it seems the limit is about 80 feet or some 25m. That distance is fine for my usage, especially if this is the only lens I have on the trip I am planning. For anything else, I can use either one of the other GM long lenses to get more reach.

We still want to get the AF and the exif data, although the effective aperture and FL
...Show more

Wow, did you have a bad day?
I know this is regarding the 300. I know shorter focal length have infinity reduced by tubes more than longer focal lengths.
This has been covered in the thread, which I did read.
I also read 10mm is too short, so 16 was used.

If 80 feet is good for you, is it so offensive that I speak of maybe increasing that. Should I have started a different thread?

Why go straight to 'butcher' ?
The tubes are very cheap. Cheap enough to inspect and see how the electrical connection is made.
It's not impossible that shortening the length of tube could be done and electrical connection maintained.
This would be called modification. Lathes are precise instruments.






Jun 12, 2024 at 07:34 AM
AGeoJO
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p.1 #18 · p.1 #18 · New 840mm lens?


Choderboy wrote:
Wow, did you have a bad day?
I know this is regarding the 300. I know shorter focal length have infinity reduced by tubes more than longer focal lengths.
This has been covered in the thread, which I did read.
I also read 10mm is too short, so 16 was used.

If 80 feet is good for you, is it so offensive that I speak of maybe increasing that. Should I have started a different thread?

Why go straight to 'butcher' ?
The tubes are very cheap. Cheap enough to inspect and see how the electrical connection is made.
It's not impossible that shortening the length of
...Show more


Not at all! Is what I wrote offensive to you? I didn't mean to do that at all. I have 2 (two) left hands and I don't have the proper tools/equipment to modify the extension tube. The term "butcher" I used applies to me since I know that I would be doing exactly that if I attempt to do the modification. It is a futile exercise for me. Your mileage may vary.



Jun 12, 2024 at 07:45 AM
IndyFab
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p.1 #19 · p.1 #19 · New 840mm lens?


Have you tried 300 + 2TC in crop mode, instead of adding the 1.4 ?

At times I will use the 200-600 + 1.4TC + crop mode and get good results.




Jun 12, 2024 at 08:28 AM
IndyFab
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p.1 #20 · p.1 #20 · New 840mm lens?


IndyFab wrote:
Have you tried 300 + 2TC in crop mode, instead of adding the 1.4 ?

At times I will use the 200-600 + 1.4TC + crop mode and get good results.



Joshua I continually/regularly get results like this using A1 - 200-600 + 1.4TC + crop mode, of course when there's good light



Likewise it works equally well using Canon R5 Sig 150-600 + 1.4 + crop mode




Jun 14, 2024 at 06:44 AM
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