Actus and ACB-310 (wide bellows for the Sony a7 series)

[freaklikeme]

I know this will probably be of limited interest to the forum on the whole, but since my ACB-310 didn't come with instructions, I thought I'd put up some reference photos. Here's the new rear out of the box next to the standard kit.

Actus_ACB310_1 by Bradley Clemens, on Flickr



First step is to remove the bellows. Then adjust the geared focusing so the rear standard is as far back on the camera as it will go. This will give you room to work. Then slide rear standard back on the rail until the stopping screw is visible in the hole, like so...

Actus_ACB310_2 by Bradley Clemens, on Flickr



Completely remove the screw using a 1.5mm torque wrench.

Actus_ACB310_3 by Bradley Clemens, on Flickr



Slide the existing rear standard off, slide the ACB-310 on, replace the stopping screw, and... voila! Wide angle nirvana (or as close as you're going to get to it without popping for the Actus DB and a digital back).

Actus_ACB310_4 by Bradley Clemens, on Flickr



It'll be a pain to haul around the extra rear standard and bellows to switch between the two, but I will probably do it since changing them is so field-friendly. Also, the amount of extension possible should allow for the use of, at least, 645 lenses with the appropriate lens plate, so there's that option as well. I can't wait to get out this weekend with the APO-Grandagon 45 and see what it can do.

 

[rjp85]

So, if you mount a 32HR with the Sony, can you do any tilts/swings, or is just to shoot with no movements?

 

[jlm]

i have the db version and was able to focus a 28mm at inf, using the CFV50c and the wide angle bellows.

what exactly is different between the two types of rear standards, and are you going to mount a 35mm camera body to the DB standard?
thx

 

[freaklikeme]

So, if you mount a 32HR with the Sony, can you do any tilts/swings, or is just to shoot with no movements?

Physically, you'll probably be limited to a few degrees in any direction at infinity, with hyperfocal distance getting you a bit more. I'd say the bigger question would be how much color shift and smearing are you willing to put up with to use that wide a lens outside of the center of the IC.

 

[freaklikeme]

i have the db version and was able to focus a 28mm at inf, using the CFV50c and the wide angle bellows.

what exactly is different between the two types of rear standards, and are you going to mount a 35mm camera body to the DB standard?
thx

Yes, getting full use of the wider lenses is just one of the many advantages of using a DB with the Actus. Not having to worry about a bayonet mount and, for Canon and Nikon, a mirror-box, makes it possible to use the lenses that require the rear element to be 21mm or less away from the image plane when focused at infinity. I don't have a DB standard, or a DB, and while I would appreciate the greater coverage of a larger sensor (to the point where the 45 would probably be as wide a lens as I'd want) I have my doubts about giving up the ease of the focal plane shutter.

The original rear standard has a rotating mount, and is designed to be interchangeable with the other 35mm mounts, the necessary bulk of which pushes the sensor back from the front of the rear standard. In the Sony configuration, this leaves you with a little less than 30mm of unusable space between the sensor and any lens. So to figure out what lens you can use with the original standard (with movements at infinity) you need to take the flange distance, subtract the length of the rear element (flange to end), and make sure the result is greater than 30mm. So the APO-Grandagon 55, with a flange distance of 67.6mm and a rear element length of 32mm, will work because it allows 35.6mm between the end of the lens and the sensor. The 45 (55.5-30=25.5) won't.

To take full advantage of the Sony's shallow registration, Cambo made the ACB-310. It does away with rotating mount, so the Sony is always in landscape orientation, and integrates the mount into rear standard and bellows, which gives you back about 8mm. Not quite enough for an APO-Grandagon 35 or SK 28XL, but it does make a few lenses that interest me possible. I think my next lens will be the SK 38XL, which seems to have a good reputation among digital back users.

 

[freaklikeme]

I spent some time this weekend scouting Eldorado Canyon State Park for locations, as I'm planning to spend a week shooting it in early autumn. It was the perfect excuse to give the new rig and lens a go. Both are six shot panos at f/11.

a7_Actus_Rode45_EldoradoCanyon1 by Bradley Clemens, on Flickr



a7_Actus_Rode45_EldoradoCanyon2 by Bradley Clemens, on Flickr