I'm considering purchase of Sigma 70-200 is along with a 2x teleconverter for a trip to Svalbard next year. Will be trying to photograph polar bears without getting too close.
Does anyone have any experience or advice on this set up. Appreciate will drop to f5.6. How much will images deterioate and are ther any alternatives I should consider.
Any help greatly appreciated
#1. "RE: D5200 & 2x teleconverter" | In response to Reply # 0Sun 13-Oct-13 11:24 PM
Welcome to Nikonians!
For the best performance, you should use a Sigma TC with the Sigma 70-200mm f/2.8. While all TC's degrade Image Quality the slower AF speed when using a TC will be more of an issue.
Have you considered renting an Nikkor 80-400, 200-400, or Sigma 50-500mm, 150-500mm for your trip?
Even the Sigmas at f/6.3 will AF faster and more accurate that the 70-200mm w/ 2X TC.
#2. "RE: D5200 & 2x teleconverter" | In response to Reply # 1Lazy Butcher Registered since 12th Oct 2013Mon 14-Oct-13 03:50 AM
Thanks for the advice
Had considered the Sigma 50-500 but was concerned over low light focusing. Not much weight difference between the 2 Sigmas when you add in weight of teleconverter.
#3. "RE: D5200 & 2x teleconverter" | In response to Reply # 1Fri 18-Oct-13 06:38 PM
I have the Nikon 55-300 kit lens. I was considering the 1.4 Nikon TC, but your warnngs have shut that down. Yes.
Renting DOES seem better, but only if used just a few times. A week of rental, plus damage waiver, is a little under $100. Spending $1200 to $2000 to buy it makes sense if you are a dedicated birder or are otherwise going to use it a lot.
Another advantage to renting is that if you find "it's just not for you", take it back, and no harm done.
If you have the pockets, you can experiment with lots of different lenses. Maybe even find one that excites you. That's my plan.
BTW, read in NPhoto Magazine about using your telephoto for bokeh close up. I experimented with mine. At aperture 5.6, and 250mm, you get GREAT bokeh. You just have to be a little farther from your subject. Give it a try!
#4. "RE: D5200 & 2x teleconverter" | In response to Reply # 3Tue 22-Oct-13 03:17 PM
Having photographed bears in Grand Teton Nat. Park with the Nikon 80-400 on a D200, I recommend the Sigma 50-500. Normally bears pretty much ignore humans (not always true of course, we do make a nice snack) so you never know how close you will be to one. Sometimes they are far away and then one will walk by 20' away that you didn't even know was there. They have the knack of walking silently.
One instance we walked around a corner and four people were standing still in the trail. They were watching a grizzly browsing for berries through the brush inside the forest. While we all stood still, the bear walked within 20' of me and yet the bear never even glanced at us. At least we didn't think so. With the locations of a bear's eyes on the side of its head, perhaps it was watching.
#5. "RE: D5200 & 2x teleconverter" | In response to Reply # 4Fri 25-Oct-13 08:32 PM
Ah, bears. So many stories of people being eaten. A predator, using common sense, will prey on what he/she considers 1. easiest to catch, 2. easiest to kill without injury to the predator, and 3. of greatest food value. A 200 lb male human is about 100 lbs or so of usable meat, can't run half as fast as a bear, and wouldn't be able even to bruise a bear, without serious weaponry, which is forbidden in parks. Hi-pri food. I don't care about your PhD, or your charity work, or that you're crucial to your community. You're 100 lbs of usable meat to a bear. Further, "the authorities" care a TON more for that bear's life than they do yours. Be outraged all you want, but that's part of the change wrought by the environmental movement. Enter at your own risk, and don't cry as you die. Bears. And they're FAST!
I researched whether teleconverters would work with my 55-300mm "kit" lens. No. They are intended for your hi-dollar f/2.8 or f/4 telephotos. You can damage your lens if you try to fit a cheepa lens. http://www.nikonusa.com/en_INC/IMG/Assets/Common-Assets/Images/Teleconverter-Compatibility/EN_Comp_chart.html
Another option I considered was your cheapo 2x telephoto "screw-on" lens. My eyebrows got singed by the flame reviews, so I'll leave that alone.
No escaping the expense, I guess.
#6. "RE: D5200 & 2x teleconverter" | In response to Reply # 5Fri 25-Oct-13 09:02 PM
The Kenko teleconverters will work with your lens and they are about half the price of the Nikon converters which won't work. You can often find the older generation Kenko models for even less. However your camera will not autofocus that lens with any teleconverter.
A lot depends on how large you intend to view your pictures and whether you want to enjoy the photos or are a pixel peeper.
When standing at what is considered the proper distance for viewing art, a photograph or a television (roughly 1.5 times the diagonal of the image), the limit of human resolution is 3 megapixels or a 720P TV. Of course if you are primarily interested in posting images on a web site or sending as emails then you can crop even more. Non-professional web sites drop the resolution to around 1 megapixel and then heavily compress.
Hence you can probably crop your 300mm image by 50% which yields the same as a 600mm lens or 900 after the equivalency factor is taken into account. 900mm is an 18 power telephoto. This would look fine on a print or large screen TV (when viewed at the proper distance). For web posting, you can easily crop that in half again.
Things to consider:
1. At that magnification, the camera/lens should be on a tripod. But hanging that lens on the body on a tripod could very well damage the lens mount on the camera so I personally wouldn't do it.
2. Even with VR, you'll want the shutter speed to be at least 1/1000th second.
3. Use an optimal aperture for that lens, typically around f/11.
4. The above combo might result in a rather high ISO but it should clean up nicely in Lightroom.
5. Some camera models (I'm not familiar with the D5200) have auto-ISO which works in manual exposure as well as the automatic modes. So you can turn on auto-ISO and choose manual exposure on the mode dial. Set the lens to f/11 and the shutter speed to 1/1000th and the camera will choose the appropriate ISO.
6. Consider replacing your lens with the 70-300 VR as that is a considerably sharper lens. You should be able to find a mint copy on CraigsList for around $300 and sell yours on Amazon. Like the 18-xx lenses, the 55-300 and 55-200 are really bottom feeder lenses. When I had a 70-300, I was able to crop to the equivalent of 1200mm (24 power) and view the images on our 50" plasma TV with the same detail as an uncropped image. This lens at 200mm is actually sharper than some of Nikon's pro lenses when stopped down to f/11. I only sold mine because of the lack of a tripod mount.
#7. "RE: D5200 & 2x teleconverter" | In response to Reply # 6Fri 25-Oct-13 10:45 PM
I PRINTED THAT POST!
Even paying retail for it would be rewarding! Which teleconverter do you mean? There is the 2x Pro 300 and 2X TelePlus. Which is best for my "bottom feeder 300"
70-300, Nikon, right? As of today, less than $300, used, on Amazon? That's actually reachable.
#8. "RE: D5200 & 2x teleconverter" | In response to Reply # 7Sat 26-Oct-13 03:38 AM
Yes, I'm referring to the Nikon and not the other brands which are rather poorly rated, your current lens is at least as good. I've nothing against the other brands for the right lenses and take over half of my pictures with a Sigma 180 macro but their 70-300 leaves something to be desired.
But, the first thing I would do is take some pictures with your current lens at 300mm and try cropping. It could be that you will be happy with that and it is free. Many people are quite happy with the lens you currently own and just don't think about cropping the images to simulate a longer zoom. This is the technique used by the cameras with "electronic zoom" settings. Also remember to shoot around f/11 to get the highest resolution.
If you are almost but not quite happy with this solution then I'd go with the Nikon 70-300 VR (make sure you are looking at the VR version of the lens, the prior version is not as good as your current lens). This will be noticeably sharper based on reviews I've read. While I owned the 70-300, I've never owned your lens for a direct comparison. Hence my recommendation in the first paragraph. The VR in this lens is also better than the 55-300. As an aside, Nikon makes 3 grades of VR from the kit level such as the 55-300, to the mid-quality lenses like the 70-300 to the pro lenses like the 200-400.
I've not used either of the Kenko teleconverters, just read about them on the lens forums. Of the two, the Pro 300 is the best rated. However your f/5.6 lens will now be f/11 wide open and that is very dark for manual focusing. As I noted before, the camera will not autofocus this combo. Personally I wouldn't find it usable though some do. You might read some of the reviews on the "Filters & Lens Accessories" forum, lots of good info there. My research had primarily been to use the Kenko Pro 300 2X on my Nikon 80-200 f/2.8D and not for the lenses you are considering.
#9. "RE: D5200 & 2x teleconverter" | In response to Reply # 8Sat 26-Oct-13 04:36 AM
Please note that this is my second response to your latest questions, please see that one first.
Here are 4 samples taken one overcast winter day from our porch here in CO. Note that it is not possible to analyze the quality of images attached to this site as they are limited to 300K and this results in heavy compression. If you would like, shoot me an email and I'll send you the full size images.
Attachment#1 (jpg file)
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Attachment#4 (jpg file)
#10. "RE: D5200 & 2x teleconverter" | In response to Reply # 9Sat 26-Oct-13 10:29 AM
It always gravitates back to the f/2.8 D or G glass. You're not the only one who infers this.
As a non-sequitur, I've found the 55-300 SUPERB for indoor photography. At the lower f, you get great bokeh. Without getting in someone's face, you can do wonderful framing for personal snapshots. The cropping is pre-shot. The 55-300's resolution and IQ at short range is superior to the 18-55 kit lens. Even though you need higher ISO, it doesn't seem to impact quality if your lighting decisions are good. Mine are improving.
In macro mode, with the d5100, short range with the 55-300 does tack sharp, brilliant work with mundane subjects. Way better than the 18-55.
The only drawbacks are an inability to properly autofocus at lower light, and the weight. If you adopt a different grip, supporting the lens, and are willing to manually focus, you get great pictures.
I've been taking medium range pictures with it, and prefer it to the 18-55. The 18-55 seems to LACK something. I lack the experience to name it. The 55-300 just seems to take better pictures at medium range.
I think, if I want to upgrade to prime glass, the Nikon 17-55 f/2.8 would be the choice, though I'd strongly consider Tamron and Sigma, as they cost significantly less. As I'm retired, such a purchase is a once a year thing, if no emergencies arise to claim the money. For sure, I'll rent before I buy.
Back to the teleconverter. My pictures, at most, will be printed 8x10 for some shots, RARELY 24" if REALLY exceptional. Usually, they'll be seen on a 17" or 21" monitor. That said, IQ may be satisfactory. What I need to work on is pre-shot composition and lighting choice, and post-processing with PSE and Photomatix.
Maybe I'll just plan in prime glass, and forget teleconverters, for now. And, for now, the 55-300 is becoming my go-to glass!
#11. "RE: D5200 & 2x teleconverter" | In response to Reply # 10Sat 26-Oct-13 02:56 PM
You said "What I need to work on is pre-shot composition and lighting choice".
You're on the right path! Great photography is 99% skill and 1% equipment. One of photography's famous mantras is "great photographers take great photos with less than stellar equipment but mediocre photographers take mediocre photos with great equipment."
BTW, "prime glass" means non-zoom such as the 55mm f/1.8 and not the 17-55 f/2.8. Again the 17-55 is not a lens that I've owned but from comments made by professionals and various reviews, this lens doesn't seem to satisfy. Users of the Sigma 17-50 seem to be more satisfied and the lens is half the price.
For most of the history of photography, we didn't have zoom lenses. The first couple of decades of zooms were poor at best. You might consider going with prime lenses as they are much higher quality and less expensive. A 50mm f/1.8D and 24mm 2.8D in excellent condition would only cost under $300 for both of them though if your body doesn't have a focusing motor then they would be manual focus. Then again, I find that I have to always correct the focus anyway as the camera doesn't know what point I want to be sharpest.
Enjoy your shooting,
#12. "RE: D5200 & 2x teleconverter" | In response to Reply # 10Sun 27-Oct-13 06:14 AM
>It always gravitates back to the f/2.8 D or G glass. You're
>not the only one who infers this.
Bill, provided images captured with the 70-300mm f/4.5-5.6 which is far from f/2.8 "Fast Glass"
>The only drawbacks are an inability to properly autofocus at
>lower light, and the weight. If you adopt a different grip,
>supporting the lens, and are willing to manually focus, you
>get great pictures.
I hold the camera the same way regardless of the lens I have mounted on it. This includes lenses ranging from the 18-55mm (3.1"L x 2.9" Dia. 9.3oz) to the 200mm f/2 (8"L x 4.9" Dia. 103.4oz). The 70-200mm (8.2"L x 3.4" Dia. 54oz) and the 200mm f/2 are significantly larger and heavier than your 55-300mm (4.8"L x 3" Dia. 18.7oz). You might find On Handholding Technique very helpful.
>I've been taking medium range pictures with it, and prefer it
>to the 18-55. The 18-55 seems to LACK something. I lack the
>experience to name it. The 55-300 just seems to take better
>pictures at medium range.
The 55-300mm is faster at the wide end (55mm) than the 18-55mm is at the long end (55mm) which could be part of the reason that you like it more. If you are shooting longer than 55mm it could be the narrower FOV that makes the images more pleasing to your eye.
The 35mm format classic portrait focal lengths range from 75mm to about 200mm (50mm - 133mm DX format). While there are exceptions, wider focal lengths don't usually flatter the human form.
>I think, if I want to upgrade to prime glass, the Nikon 17-55
>f/2.8 would be the choice, though I'd strongly consider Tamron
>and Sigma, as they cost significantly less. As I'm retired,
>such a purchase is a once a year thing, if no emergencies
>arise to claim the money. For sure, I'll rent before I buy.
The 17-55mm (4.4"L x 3.4" Dia. 26.6oz) is optically excellent and the perfect wide angle to short telephoto on a DX body. For weddings and low light events it is a go to lens for many DX shooters.
>Back to the teleconverter. My pictures, at most, will be
>printed 8x10 for some shots, RARELY 24" if REALLY
>exceptional. Usually, they'll be seen on a 17" or
>21" monitor. That said, IQ may be satisfactory. What I
>need to work on is pre-shot composition and lighting choice,
>and post-processing with PSE and Photomatix.
While the Kenko 300 series TC's will work on your 55-300mm the AF speed will slow significantly in excellent (bright) ambient light and not work at all as the ambient light level decreases. As with any TC, the higher the magnification the more the IQ will decrease.
>Maybe I'll just plan in prime glass, and forget
>teleconverters, for now. And, for now, the 55-300 is becoming
>my go-to glass!
As long as cropping works for your requirements, that makes perfect sense.
#13. "RE: D5200 & 2x teleconverter" | In response to Reply # 12Sun 27-Oct-13 10:04 AM | edited Sun 27-Oct-13 11:48 AM by buffumjr
Great advice, guys, thanx.
So, I'll save the 18-55 for shotz requiring wide angle, and use the 55-300 for most all else.
BTW, a machining project, or half of it, the restoration of a Veco .61 R/C model airplane engine. It arrived no plug, no prop washer, the con rod bushings shot, and no carb. It is now start ready. Carb made from scratch. The needle valve and spray bar by Fox Mfg. I added the muffler, made from scratch.
3 photos. 55-300mm Nikon "kit" lens at 250mm manually focused, d5100 in macro mode, El Cheapo MX 3000 tripod, no post, no cropping.
LOVE Photobucket. NO struggling with forum posting rules, no matter which forum.
#14. "RE: D5200 & 2x teleconverter" | In response to Reply # 13Sun 27-Oct-13 11:45 AM | edited Sun 27-Oct-13 12:28 PM by buffumjr
I looked up the Sigma 18-50mm F/2.8 EX DC Lens and the Sigma 18-50mm f/2.8 EX DC SLD ELD on Amazon. 1/4 the price of the Nikon offering. I'll try hard to find it as a rental, and try it out! $340 is do-able.
BTW, what is the difference, or did one item just fail to add the "SLD ELD" to the description?
Found out Sigma also makes a 17-50mm f/2.8 EX DC OS HSM FLD . So many choices!
#16. "RE: D5200 & 2x teleconverter" | In response to Reply # 14Sun 27-Oct-13 05:13 PM
The confusion is easy to understand.
Since here have been a several versions of the 18-50mm over the years.
18-50mm f/2.8 EX DC(580), 18-50mm f/2.8 EX DC Macro(581), and 18-50MM F/2.8 EX DC Macro HSM(582).
The current version is the 17-50mm f/2.8 EX DC (OS) HSM(583).
To add more confusion, you can add the discontinued 17-50mm f/2.8-4.5 DC Macro(669), and the 17-70mm f/2.8-4.5 DC Macro(689), and the current 17-70mm f/2.8-4 DC Macro OS HSM(668)to the list.
#17. "RE: D5200 & 2x teleconverter" | In response to Reply # 15Mon 28-Oct-13 11:49 AM | edited Mon 28-Oct-13 12:14 PM by buffumjr
>Very nice work on the engine restoration.
Thank you. It was fun.
Veco .61 R/C. Never done a carb before. Did a venturi, once, but not a carb. The model airplane these engines pull, controlline, 50-60 inches stunt, 40 inches and up scale. R/C as big as you want to build 'em, as long as you keep the weight to about 4 lbs. 6 feet, 7 feet, 8 feet. There's an "old timer" free flight, converted to R/C, 10 feet wingspan this would pull handily. "Nimbus" 1937. Kind of hard to transport in a Smart or a Fiat, though
Back to the 17(18)-50mm f/2.8. I notice Tamron makes one, too. That means Nikon, Sigma, and Tamron. Sigma and Tamron equivalent price. Nikon extravagant. Got about 1/4 the $$ saved for Sigma or Tamron. Will buy from my brick and mortar store. They give a 90 day warranty on used. Trading in my 18-55 "kit" lens should further lessen the impact. 17-70mm f/2.8-4 DC Macro OS HSM(668) sounds REALLY good.
This purchase will be before considering a teleconverter, if I ever do. But then, manually focusing is no big deal. In fact, to be desired, as the camera doesn't always make the right choice on what to consider in focus. I'm very happy with the 300 kit lens, so far, so whatever I buy in future has to work with the kit lens.
#18. "RE: D5200 & 2x teleconverter" | In response to Reply # 17Mon 28-Oct-13 08:51 PM
>Back to the 17(18)-50mm f/2.8. I notice Tamron makes one,
>too. That means Nikon, Sigma, and Tamron. Sigma and Tamron
>equivalent price. Nikon extravagant. Got about 1/4 the $$
>saved for Sigma or Tamron. Will buy from my brick and mortar
>store. They give a 90 day warranty on used. Trading in my
>18-55 "kit" lens should further lessen the impact.
I suspect that you won't get very much if you trade in your 18-55mm.
If that is the case, it might be worth keeping. More so if you ever want a small lightweight lens for hiking or travel.
>17-70mm f/2.8-4 DC Macro OS HSM(668) sounds REALLY good.
While the 17-70mm has slightly more range than the 17-50mm or the Nikkor 17-55mm it is a variable aperture zoom and only a stop faster than your 18-55mm at the long end instead of two full stops like the 17-50mm and 17-55mm constant aperture zooms.
>This purchase will be before considering a teleconverter, if I
>ever do. But then, manually focusing is no big deal. In fact,
>to be desired, as the camera doesn't always make the right
>choice on what to consider in focus.
Keep in mind that you should never mount a TC on a wide angle zoom like the 17-55mm. The primary reason is the rear element of the lens will likely crash into the front element of the TC resulting in destruction of both the lens and the TC.
With regard to manually focusing a slow lens like the 55-300mm with a TC:
Even in bright ambient light the viewfinder will be very dark. At 300mm the maximum aperture is f/5.6 then add 1 stop if you use a 1.4X TC or 2 stops if you use a 2X TC giving you f/8 or f/11 wide open. The result is a very dark viewfinder making Manual focus very difficult in all but the best light.
#19. "RE: D5200 & 2x teleconverter" | In response to Reply # 18Mon 28-Oct-13 10:13 PM
OK, so the Sigma 17-50 it is. The Tamron does NOT have stabilization.
So, I need an f/2.8 200 or 300 zoom to get good use out of a teleconverter. That puts THAT off awhile. Multi-thousand $$. Other items on the bucket list will claim that money.
Maybe I can just use my good ol' 300 kit lens. Lookin' better all the time. And to think, I almost substituted the 18-270 Tamron!
Today, I made a cylinder head for a Cox Tee Dee .15. I had ordered one from an outfit in Canada, but they sent the wrong one. So, I made a head that uses a short standard glow plug. My homemade 1/4-32 tap worked perfectly. I'll start both that and the Veco .61 tomorrow.
Wednesday morning, I plan a little photo tour of a nearby lake/pond. It seems to have a park on one side, or is it private property? Only one way to find out. I'm takin' both lenses, and my Canon sx160. All the toys. Ponds are great for wild life. No, not scantily clad and drunk, I'm talkin' cranes, ducks, rackety-coons, maybe even deer. We'll see how the 18-55 does, but I have a hunch I'll use the 300 more.
#20. "RE: D5200 & 2x teleconverter" | In response to Reply # 19Mon 28-Oct-13 11:56 PM
>OK, so the Sigma 17-50 it is. The Tamron does NOT have
There are at least two versions of the Tamron 17-50mm as well.
The SP 17-50mm F/2.8 f/2.8 XR Di II LD Aspherical
(Model A16) and the SP 17-50mm F/2.8 VC f/2.8 XR Di II VC LD Aspherical (Model B005). Note that VC (Vibration Compensation) is Tamron's version of Image Stabilization. From All reports the latest Tamron 17-50mm is optically excellent.
>So, I need an f/2.8 200 or 300 zoom to get good use out of a
>teleconverter. That puts THAT off awhile. Multi-thousand $$.
> Other items on the bucket list will claim that money.
The Sigma 70-200mm f/2.8 EX DG OS HSM ($1249.00 after $150.00 rebate) or the Tamron SP 70-200mm f/2.8 DI VC USM ($1399.00 after $100.00 rebate) are both optically excellent and about $1000.00 less than the Nikkor 70-200mm VR II and have true Ring motors for fast AF.
The Tamron SP 70-200mm f/2.8 Di LD (IF) Macro ($769.00) is also optically excellent. While it has an AF motor built in, it is not a Ring motor so the AF speed is significantly slower.
>Maybe I can just use my good ol' 300 kit lens. Lookin' better
>all the time. And to think, I almost substituted the 18-270
>Wednesday morning, I plan a little photo tour of a nearby
>lake/pond. It seems to have a park on one side, or is it
>private property? Only one way to find out. I'm takin' both
>lenses, and my Canon sx160. All the toys. Ponds are great
>for wild life. No, not scantily clad and drunk, I'm talkin'
>cranes, ducks, rackety-coons, maybe even deer. We'll see how
>the 18-55 does, but I have a hunch I'll use the 300 more.
#21. "RE: D5200 & 2x teleconverter" | In response to Reply # 20Thu 31-Oct-13 06:11 PM
Good photo tour. A very photogenic crane. Some interesting trees.
An interesting revalation from the park ranger. I had noticed chain link fence and signs barring visitors to the lake shore. The signs read "NO Trespassing! Violators must be arrested and removed." I asked the ranger about it. He said it's all about liability. With those signs up, and a mandatory arrest and removal policy, if a drunken you or your child falls into the lake and drowns, the city cannot be sued, as you were committing a misdemeanor by being in a forbidden area. He said their lawyers stressed the policy must be followed to the letter, that, if you merely hop over and hop back, they MUST call the police, and the police cannot issue a warning. They MUST cuff you, Mirandize you, and stuff you into a squad car.
I imagine, some lawyer, somewhere, could figger out how to sue, but it would be a tall hill.
Being denied the shoreline, except for the boat ramp, there wasn't a whole lot of bird activity. I got what could out of the crane. I exercised my 55-300 "kit" and my 18-55 "kit".
I found out my Promaster 7100 tripod cannot hold the 300 level. It does fine with the 18-55. I'm going to have to make a counterweight, or buy a better tripod. More machining!
#22. "RE: D5200 & 2x teleconverter" | In response to Reply # 21Fri 01-Nov-13 10:11 AM | edited Fri 01-Nov-13 04:45 PM by buffumjr
After much thought, the counterweight solution is easy stuff. Figure out how to hang a simple one pound weight on the pan handle of the tripod. When I'm done with the 300, remove the weight.
Went on the tripod forum, and found out the $$ solution to all this will cost at least a G-note. Still a better hobby than boating. B.O.A.T. (Break Out Another Thousand)
The recommendation seems to be very high end Manfrotto, Gitzo, or Giotto, then there were a few recommendations for the head.
If I am ever to do telephoto, with a teleconverter, the purchase of a good, solid tripod must come first.
The upside is my cheapo MX3000 and my Promaster 7100 will be excellent as lighting tripods for when I start trying studio stuff.
#23. "RE: D5200 & 2x teleconverter" | In response to Reply # 22Mon 04-Nov-13 09:33 PM
You would be better off machining a bracket to allow you to vari the offset between the cameras tripod socket and the the 1/4"-20 screw on the tripod head.
That way you can keep the cameras center of mass centered on the head.
At 300mm your tripod is already exceeding the focal length capacity by more than two times. Adding a counter weight will just add more load to the tripod and reduce what little stability you have even more.
The Promaster 7100 has a leg diameter of 23mm.
The Gitzo Tripod Configurator indicates that the maximum recommended focal length capacity for a 1-Series tripod (24mm diameter legs) is 135mm.
Adding a quality tripod and ball head would be a better place to start but not easy on a tight budget.