Lens – Kevin Davis Photography

How to replace the lens of a GoPro Hero camera

June 11, 2014June 11, 2014Kevin

The lens included with a GoPro Hero 3+ has a focal length of 2.5 mm and has a field of view akin to a 14mm lens on a full-frame DSLR. It is “fisheye”. You can set the camera to a narrow capture setting, but this will crop the image, discarding some of the pixels.

Replacing the lens mount in a GoPro Hero3+

Super wide is fine if you are attaching the GoPro to your helmet or a surfboard. For me, the stock Hero3 lens is too fisheye and I want a narrower field of view.

There are many available replacement lenses, but most lack the quality required to capture 10 megapixel images. Most lenses are good enough quality to capture 5 megapixel images. I found two companies that sell a 5.4mm lens, having a 60 degree field of view, and rated as being sufficient for 10 megapixel images: RageCams (USA) and Vision/Dimension (Germany).

On paper, these two products seem equivalent, but there are a few important differences.

The 5.4mm lens from RageCams is easier to install. The lens from Vision/Dimension requires disassembling the camera and replacing the lens mount.
If you do it yourself, the cost of a 5.4mm lens from RageCams is higher than the cost of a 5.4mm kit from Vision/Dimension.
If you don’t want to mess with the camera yourself, you can pay RageCams to do the replacement for you. The cost of parts and labor is more than the cost of the GoPro Hero3+ camera
The Vision/Dimension lens includes infrared filter for daylight use. The RageCams web site states that an IR filter will cost you an extra $55.

Huh? What’s the problem deal with the lens mount?

The lens mount is a standard M12 lens mount, a simple threaded barrel. To change the lens, you theoretically unscrew the existing lens and screw in another lens. However, if I understand this correctly, there is a subtle quirk to the GoPro lens mount, which may mean that your new replacement lens will not focus properly. The lens mount is a female-threaded tube, but apparently the full length of the tube is not threaded; the front-most part lacks threads. If your new replacement lens has a short barrel length, you will be able to screw it in, but the distance to the image sensor will be too close for proper image focus. The 5.4mm lens from RageCams has a slightly longer barrel than the same lens from Vision/Dimension.

Lens replacement options

Option 1:
Ship your GoPro Hero camera to RageCams and have them replace the lens. This is both the simplest option and the most expensive option.

Option 2:
Buy a replacement lens from RageCams and replace it yourself.

To grip the lens with a pliers, you first need to remove the decorative plastic ring on the outer body of the GoPro. This part is quite simple and you can find videos on YouTube that show how it is done.

The lens is fixed in place with a bit of thread-lock. To unscrew the lens, you probably have to apply heat to the lens with a heat gun (without melting anything). Again, there are helpful videos on YouTube.

Option 3:
Buy a replacement kit from Vision/Dimension and replace it yourself. This kit includes the lens and a lens mount that is fully threaded. Replacing the lens mount is a bit difficult
www.vd-shop.de/instruction-replace-gopro-lens-a-80.html

Option 4:
Install an adapter that allows you to use almost any lens. While this enables the use of high-quality lenses and allows the use of variable-aperture lenses, it necessarily makes your GoPro physically larger and heavier. Refer to this link: www.back-bone.ca

I bought the Vision Dimension kit. While the price of this kit seems significantly less than cost of a comparable lens from RageCams, there are hidden costs. Shipping from Europe to the USA cost me $45 and then I received a bill from Federal Express for an import duty of $20. In the end, buying from Vision Dimension did not save me as much money as I had thought it would.

Looking at the photo at the top of this blog, you can see “10MP” (10 megapixel) is printed on the lens. Also printed on the lens (not visible in this photo) is “IR Cut”, indicating that a daylight IR filter is present.

Disassembling a $400 camera, that has really tiny parts, is not a task for the faint of heart. A video from Vision Dimension demonstrates the procedure; you can view that before making your decision. To avoid this hassle, pay a bit more money and buy the lens from RageCams.

If you replace the lens yourself …

You have somehow replaced the lens … and now need to adjust it for sharp focus.

Start by setting the approximate focus; load the GoPro app on an iOS or Android device to achieve a live preview of what the camera is seeing. When the focus looks good, here is an extra step to ensure that the focus is as good as possible.
Temporarily make a few markings on the outside of the lens; I attached five small pieces of white tape. Adjust the lens to each mark, one at a time, and capture a photograph.
Study the resulting photos at high magnification and pick the sharpest photo. Adjust the lens to the corresponding lens mark.
Repeat the procedure on a finer scale. I captured three photos, one on center, one slightly to the left, and one slightly to the right.

You do need a dab of glue or thread-lock to prevent the lens from turning inadvertently. You might put this on the threads before inserting the new lens. I was afraid that this might inhibit lens adjustment, so I adjusted the lens first, then unscrewed the lens, added a dab of glue to the threads, and re-inserted the lens. The trick to this is to count the number of revolutions when unscrewing the lens, so that you can easily get back to the point of sharp focus. Personally, I counted 13.5 turns of the lens. (In retrospect, the glue I used did not set quickly and I could have applied it before first inserting the lens.)

Finally, note that the new lens sticks out a bit further from the Hero camera body, compared to the original lens. It’s probably not going to fit in the waterproof housing. The Vision Dimension kit includes a spacer ring that you put between the Hero and the housing. The RageCams web site advises that you remove the foam cushion from the rear door of the housing.

In the end, I am disappointed with the image quality from the Hero3+. While I believe this is largely due to the camera, I have not as yet proven/disproven the claim that this lens is good enough for 10 megapixels.

Inexpensive Ultra-Zoom Lens

June 29, 2013July 25, 2013Kevin

For most of us, the need for an ultra-long lens is infrequent … but when you need it, you need it!

I’ve written about this before … Ultimate Lens for Sports & Wildlife … and … Novoflex SuperTelephoto.

One of those posts regarded the yet-to-be-available and much-to-be-desired Canon 200-400; that lens is now available.

This week, I have had two different needs for a long lens.

Photographing wildlife. I will be at a game ranch next week. I must choose and rent some long telephoto glass. (If this need arose more frequently, I would purchase/own it.) What lens choices available to me?

First, note that there is generally a trade-off between any fixed-focal-length lenses (non zoom) that have wide aperture (gathers more light) and zoom lenses, which provide variable focal length but sacrifice a bit with regard to aperture. I would love to have multiple long lenses at my disposal; but if I must choose one, then the flexibility of a zoom is the safe choice.

Zoom options. Top of the list is that new 200-400. Hands down, that is the lens I want to shoot with. The problem is the price tag; the rental fee is over $600 and purchase price is more than $10,000. This leaves me with a choice of the Canon 100-400 f/4.5-5.6L, Canon 100-300 f/4.5-5.6L, that same 100-300 plus a 1.4x teleconverter, or possibly a third party lens such as Sigma.

Multiple reviews across the internet all agree that the 100-300 is a superior lens compared to the 100-400. Unless you need the extra reach of 400mm. Apparently the 100-300 is not compatible with Canon teleconverters. So I chose the 100-400.

Photographing an ocean event from the shore. The event this week was the Greasy Pole challenge at the St. Peter’s Festival in Gloucester. For this event, I opted to test something new with a small camera, specifically, my micro four-thirds (MFT) camera, a Panasonic Lumix G3.

All micro four-thirds cameras use an image sensor that is the same size and is half the size of the sensor in my DSLR. A 200mm lens on the smaller camera is like putting a 200mm lens on the larger camera and then cropping the image to ½ size. It is called “crop factor”, but it implies that the smaller sensor size makes a 200mm lens seem like 400mm. Image quality of my MFT camera is very good, but significant image noise is present at ISO 800 (because the image sensor jams pixels into a much tighter space).

My zoom lens for MFT goes up to 200mm. For whatever reason, neither Olympus nor Panasonic offer a real teleconverter for MFT. So I tried a 1.7x teleconverter that threads on to the front of the lens. If we ignore the fact that the sensor is small, the result is akin to 1300mm. Or considering the small sensor size, it is like shooting a full-frame camera with a 680mm lens and then crop the image to one half size (you get fewer pixels, but it looks like zoom).

[Click on any of the included images to see a larger view.]

The sample images shown abive are (1) without the teleconverter and (2) with the teleconverter. The teleconverter is worse than I had hoped; it causes very significant loss of sharpness and contrast. Is this acceptable? No, not for me. But the teleconverter was a remnant piece of equipment (from a deceased video camcorder) that was collecting dust at home and cost me nothing to try it.

The last image shown here is shot without the teleconverter and then cropped to achieve the same perspective as though I had used the teleconverter. The result has far fewer pixels than originally captured by the camera. Using computer software, I then artificially increased the size of the image, to arrive at a 10-megapixel image with far better image quality than when shot with the teleconverter.

So, for situations like this one, where auto-focus is not particularly important, I come to the same conclusion as before. An old/used telephoto lens for any SLR, with an adapter to fit it onto a four-thirds or micro four-thirds camera.

And my best MFT solution that includes auto-focus, would be the Panasonic 100-300/4-5.6 Lumix G Vario (cost roughly $600).

Photographing Freestyle Ski Jumping

January 15, 2013April 6, 2018Kevin

Very excited to photograph freestyle ski jumping this week!
For photography, winter can be dull, particularly if there is no snow … the grey season, the season of sticks without leaves. But NOT this week. This is an international event sponsored by FIS, the international skiing authority. The ORDA has authorized official Press credentials, which allows me a bit more freedom of movement than regular spectators, to achieve shooting angles I need to create good images.

Because the freestyle ski jump competition is preceded by a mogul competition, I will arrive a day early in order to catch the mogul competition. Although I don’t “need” this shoot, I’m going to be right there and it could be fun (I simply haven’t thought about it much). One extra night’s lodging is all it takes … and maybe rent a pair of skis so I can reach the top & middle of the slope.

Logistical arrangements have required a significant investment of time.

Lens selection & rent
A couple of (smaller) equipment purchases
Contact ORDA for official Press credentials
Find a place to stay (difficult because I made a reservation only 1wk prior to the event)
Couple minor things regarding my car (before driving 500 miles)

(The weather forecast for Friday is *COLD*.)

I have selected a 70-200mm f4 zoom lens and the Canon EF 400mm f4 DO lens. Having never used the DO lens before, this is a bit of a gamble. However, at 4.27 lbs, the DO is significantly less weight than the 400mm f2.8 or even the 300mm f2.8.

While the weight of the 400mm DO is hand-holdable, I want a monopod so that I do not have to hand-hold it. But my cheap old monopod (really cheap) is not enough for this task. So I purchased a new monopod (Feisol). With this particular item in mind, I went to my local photography shop (Hunt’s Photo & Video) and looked at the other options (Benro, Induro, etc). Lucky for me they did stock the Feisol and that is ultimately the item I had in-hand when I left the store.

When used on snow, a monopod (or even a tripod) will punch a narrow hole in the snow and sink, because of the very narrow footprint. A few monopods do have an expanded “foot”, but the model I selected does not have this feature. So I cut up the plastic lid to a peanut butter jar and attached that to the bottom of the monopod.

Novoflex Super-Telephoto Lens

July 11, 2012April 6, 2018Kevin

Recently, my friend Tom loaned me a vintage Novoflex super-telephoto lens. Since he already had adaptors for both Nikon and Canon EOS, we had no trouble fitting it to my full-frame Canon DSLR.

The Novoflexar pistol-grip lens, originally made in Germany, is a bit obscure here in the USA. There were a few different models; one version has a single pistol grip, while this one here has two pistol grips. Focus control is built in to the rear pistol grip and a shutter release button on the front pistol grip (requires a cable that connects to the camera). Theoretically, this allows an agile “run and gun” type of photography, but I used it on a tripod.

The main body of the lens is simply hollow with no glass. The glass is fully contained in a front tube that threads on to the main body. Tom’s kit included a 400mm and a 600mm (some models have a 640mm instead of 600). Because there is not a lot of glass, the total package is relatively lightweight compared to some other super-telephoto lenses.

Squeezing the focus trigger moves the front tube forward and back. (Novoflex called this “Rapid Focus” or “Super Rapid Focus”.) There is no focus ring (typical on most lenses); the focus mechanism does not involve any rotation of anything. There is a focus lock, to lock the focus in one spot, which I used frequently because the distance to my subject often was very far away and unchanging. Constantly squeezing the trigger with your fingers can be quite tiring.

The focus trigger only covers part of the focus range. The trigger will not get you from minimum focusing distance to infinity. You first have to adjust one other thing, to get the focus “in the ballpark”. In some situations, perhaps this would be problematic. But on the positive side, the focus trigger is close to the camera, so you don’t have to extend your arm in order to reach a focus ring (as is true with some big super-telephoto lenses).

(click on any image for a larger view)

I used this lens wide-open. That means f\5.6 for the 400mm and f\8 for the 600mm. The 600mm showed some color fringing at hightlight edges, particularly where highlight directly overlapped a dark area. This chromatic aberation gets worse with use of the Novoflex 2x multiplier.

The lens accepts a drop-in polarizing filter. Although I tried to exchange this with a Nikon lens, the Novoflex filter and the Nikon filter were different thicknesses, so are not interchangable.

Crop from previous image.
Note the color fringe on the white shirt sleeve.

The Novoflex aperature uses 24 blades, more than double most lenses. This is probably not significant to most people. If you do get into a situation with flare, the flare will look more round, compared to the pentagram shape that occurs with a 5-blade aperature.

Conclusions

Pro

The pistol grip design may be well-suited for a mobile/agile type of photography
Price. Potentially, you might find one for less than $700 (US), but they are rare.
(If you can borrow one, as I did, then free is great.)
Weight. Not very heavy because it does not use much glass and because you get two lenses in one
Sharpness of the 400mm is good (not great)

Con

This lens dates back to the 1970s, so it is manual focus and has no image stabilization. (That’s OK when using a tripod and photographing subjects that are far away. In these situations, the pistol grip design is mostly unnecessary.)
The squeeze focus is a bit odd; I never quite warmed up to that feature.
The 600mm shows chromatic aberation (that is amplified by a 2x multiplier)
Sharpness: the 600mm seemed a bit soft to me
The pistol grip design makes this lens look like a bazooka. Particularly with the 600mm front tube, it will turn heads … possibly security or law enforcement.

If you’re looking for a super-telephoto for less than $1000. I suspect there are better options available. Specifically, the Tamron 200-500 SP AF Di LD and the Sigma 150-500 APO DG OS HSM. Both Photozone.com and BobAtkins.com have published detailed reviews of the Tamron zoom. Both Kenrockwell.com and CameraLabs.com have published detailed reviews of the Sigma zoom. (Note that the Sigma includes optical image stabilization and the Tamron does not.)

Lens replacement options

If you replace the lens yourself …

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