Monday, 10 November 2014

Jobu Micro Gimbal/Ballhead Adapter

One thing I've realised about photography is that it is a “无底洞” (bottomless pit).  You buy something, then buy something else to complement that something, and so on.  A case in point: I recently bought the Tamron SP 150-600mm f/5-6.3 Di VC USD for Nikon to shoot birds and started itching for a gimbal head.  However, gimbal heads are expensive and I don't think I shoot often enough to justify that expenditure.  Hence I decided to buy the Jobu Micro Gimbal/Ballhead Adapter which seems to be a good compromise since I already have an existing tripod with Arca Swiss ball head.

The adapter is small enough to be put into the bag and deployed as and when necessary.  But the Tamron lens presents additional challenge as it is a zoom lens.  Normally you need to mount your lens on the gimbal such that it can balance.  However, as the Tamron lens extends from 150mm to 600mm, the center of gravity will shift towards the front and upset the balance.  Since I normally shoot at 600mm, I try to balance the whole setup at that focal length, which led to another problem.

I mounted my ball head's Arca Swiss quick release (QR) plate on the lens collar and then attached it to the gimbal and slid it back to balance the setup.  But at 600mm the QR plate is simply not long enough to provide sufficient space to slide backwards.  So now I needed to go and buy a longer QR plate: Sunwayfoto Universal Quick-Release Plate DPG-120D.  Finally I can balance at 600mm:

Nikon D610 + Tamron 150-600mm
So is this the end of the story?  I chanced upon the Micro-Head Offset Adapter while browsing one fine day.  At this point in time I don't think I will be buying that unless absolutely necessary.

Thursday, 6 November 2014

Metabones Nikon G Lens to Sony E-Mount Speed Booster ULTRA

I started with a Sony NEX-6, and have since moved on to a Nikon D610.  But I am still holding on to the former as a secondary or backup camera.  However, a secondary camera that doesn't share lenses with the primary camera is of limited use.  Luckily, the Sony NEX-6 is a mirrorless camera that can accept Nikon lenses via suitable adapters.  The reverse i.e. mounting Sony E-mount lenses on Nikon DSLR is not possible though.

I decided to purchase the Metabones Nikon G Lens to Sony E-Mount Speed Booster ULTRA to attach my Nikon F-mount lenses to the NEX-6.  I like the idea of using my full frame (FF) lenses on a cropped sensor camera without worrying about the crop factor.  The speed boost of 1 f-stop and improvement in image quality simply make this adapter a no-brainer.

Of course, reality is never that rosy.  I can't autofocus with this adapter, which is not a huge loss since NEX-6 has focus peaking and manual focus (MF) assist (need to enable Release w/o Lens to work).  I also will be primarily using this adapter for landscape and macro, which suits MF anyway.

Next, there is no focal length, aperture, and lens identification info transmitted; I only know the ISO and shutter speed.  Hence if the missing info is important, I will need to record it down manually somewhere.

Last but not least, Tamron's vibration compensation (VC) doesn't seem to work, at least for Tamron SP 24-70mm F2.8 Di VC USD Nikon.  Again, not a big loss and can conserve battery life to boot!

Now let's talk about some positive things.  The increase in light gathered by 1 f-stop is real; too bad the depth of field (DoF) doesn't drop correspondingly as well.  In other words, an f/2.8 lens will become f/2 for exposure purpose but the DoF is still f/2.8.  But if my understanding is correct, this is already an improvement because normally there is a need to multiply the DoF by the crop factor to obtain the effective DoF i.e. if I am not using a Speed Booster type adapter, the f/2.8 lens will actually provide f/4.2 DoF even though the light is still gathered at f/2.8.

I looked into hyperfocal distance calculation with this adapter as well.  I believe one should use the reduced focal length (by 0.71x) and a cropped sensor's circle of confusion (0.02mm) to compute.  But since that will consistently yield results that are shorter than the FF focal length and FF sensor's circle of confusion (0.03mm), I can just use the FF calculations if that is more convenient e.g. the DoF scale on my AF Nikkor 50mm f/1.8D.

Another thing I like about the adapter is the removable Arca-Swiss foot.  Although it looks a bit too slim for comfort, it does secure to my tripod head.