Jump to content

NEX to EF SpeedBooster on A7S (using A7S Super-35 mode)


jcs
 Share

Recommended Posts

Since the A7S provides a Super-35 crop mode, it would appear the NEX to EF SpeedBooster would work with the A7S, providing another stop of light. Image quality for the crop mode should be decent as Sony appears to have a high-quality scaler.

Link to comment
Share on other sites

Sounds kinda like getting a turbo for my cars so I can go faster in low gear.

Why not use the higher gears you alrady have?

The A7s is spec at the highest ISO camera out there?

Why would it need an extra stop of light?

 

kubrick had the best cameras lenses and film stock available, yet still ripped them apart so he could use crazy nasa lenses for some of his planned shots.  

Link to comment
Share on other sites

jcs is just pointing out an interesting feature/possibility.  the speedbooster is a really fascinating thing - pairing it with a sensitive camera is a natural idea.  By putting the camera into APS-C mode, the DOF becomes a bit bigger, but the speedbooster ups the amount of light.  So you don't get insanely shallow DOF but do get the extra stop. 

Link to comment
Share on other sites

While the A7S appears to be amazing in low light, an extra stop of light means less noise and even more low-light capability.

 

Regarding turbos: car guys (& gals) can never have enough horsepower. It's like having a big V8 with a blower or twin turbos. Why add nitrous? Because it makes the car go faster  :)

Link to comment
Share on other sites

While the A7S appears to be amazing in low light, an extra stop of light means less noise and even more low-light capability.

 

Regarding turbos: car guys (& gals) can never have enough horsepower. It's like having a big V8 with a blower or twin turbos. Why add nitrous? Because it makes the car go faster  :)

 

He means: getting turbo but removing last gear.

Because you are increasing light from SB but project on smaller area (lower resolution).

 

BTW: Interesting idea if you don't want 4K.

The same FF lens with normal adapter vs SB + crop mode will give the same FOV but will look different (higher resolution pixel binning vs no-binning? + extra stop of light)

crazy! :)

Link to comment
Share on other sites

While the A7S appears to be amazing in low light, an extra stop of light means less noise and even more low-light capability.

 

Regarding turbos: car guys (& gals) can never have enough horsepower. It's like having a big V8 with a blower or twin turbos. Why add nitrous? Because it makes the car go faster  :)

 

Apparently you missed the point of the car analogy. The high specs on paper are not too practical without a matching enclosure. A high-revving engine of a Japanese crotch rocket may deliver fancy dyno sheets, especially if you turbocharge it, but it wouldn't be too practical when bolted on a Land Rover. There's a reason why they often come with a 2.5-litre diesel engine instead, even though on paper it doesn't deliver as much horsepower as the turbocharged Japanese sewing machine.

 

The bottom line is, putting a focal reducer made for a smaller sensor camera sort of defeats the purpose of having a large sensor camera to begin with. The high numbers may look impressive on paper, but what's the point? Why not going for a faster FF lens instead, and have an ideal sensor-lens match to work with. 

 

Sure, you could do that, anyway, and nothing is stopping you, but that would be quite a... um,  nerdy way to use a FF camera. I'm pretty sure a fast FF lens would be a better match optically, too. 

 

Just saying. But by all means do just that if it floats your boat.  ;)

Link to comment
Share on other sites

The A7S is really a 1080p camera: 4K requires an external recorder. It is not using pixel binning or line skipping for 4K => 1080p: it has a decent scaler (perhaps something better than bilinear, possibly cubic or Lanczos etc.). Thus, when shooting at 1080p, there shouldn't be a significant image quality difference when scaling 4K to 1080p using the full sensor or a Super-35 crop. While there will be slightly less oversampling for the Super-35 crop, there's still plenty of information for a solid 1080p image- not likely to be much difference even if shooting a resolution chart. Externally recorded 4K will be slightly softer for Super-35 scaled up to FF, however since it appears to be a decent scaler, should still look pretty good. Resolution should be similar between full frame and Super-35 crop for 1080p.

 

A 500+HP Turbo Hayabusa motorcycle engine coupled to a reduction gear would be bad-ass in a Range Rover and would sound awesome too: 

Link to comment
Share on other sites

Sometimes we try combinations because we have various components on hand: I have a SpeedBooster for the FS700- will it work on the A7S? It should!

 

While it will technically "work", apparently (on a pre-production camera) the scaler isn't that great: aliasing, moire, and reduced resolution in Super-35 mode http://www.dvxuser.com/V6/showthread.php?324956-FS700-a7S-and-a6000/page2:

 

 

the time i did test with a7S, i only had a chance to do it with "APS-C" mode with genuine E mount lens and EF mount (Canon L) lens with Metabones Smart Adapter ver.2 i've own.

 

and that APS-C mode didn't gave me the best resolution i've expected. it had minor moire and bitter highlight aliasing, and once i switched to 1080P/60fps, the footage had kinda strong moire...some sensor readout issue doing on, i think.

 

to get full potential the a7S has, better get using with FE mount lens, or your lens collection with Metabones Smart Adapter "ver.3 or 4", not with ver.1 nor 2. 

 

with full frame size lens, a7S must have beautiful moire free 1080P and UHD footage.

Link to comment
Share on other sites

This isn't like installing a turbo, its like installing an overdrive and then driving in second gear, you have achieved nothing. 

At least not in the way you thought you did.

 

You gain a stop in exposure, but you also gain a stop of noise for every given ISO so that evens out.  You may, however, get a higher exposure at a given dynamic range.

 

In terms of depth of field you are exactly were you started.  If you think you gain depth of field with a speed booster you are simply mistaken in how it works.

 

What advantage this may have is that the rolling shutter may be less in apsc crop than full frame due to less sensor needing to be read.  But this remains to be seen and it also remains to be seen what differences in quality between the modes will be.

 

Its an interesting idea though, and it will probably be a good way of comparing the crop modes.

Link to comment
Share on other sites

This isn't like installing a turbo, its like installing an overdrive and then driving in second gear, you have achieved nothing. 

At least not in the way you thought you did.

 

You gain a stop in exposure, but you also gain a stop of noise for every given ISO so that evens out.  You may, however, get a higher exposure at a given dynamic range.

 

In terms of depth of field you are exactly were you started.  If you think you gain depth of field with a speed booster you are simply mistaken in how it works.

 

What advantage this may have is that the rolling shutter may be less in apsc crop than full frame due to less sensor needing to be read.  But this remains to be seen and it also remains to be seen what differences in quality between the modes will be.

 

Its an interesting idea though, and it will probably be a good way of comparing the crop modes.

 

??

 

Don't understand the bit about exposure - the point is that you get an extra stop of light and don't have to raise the ISO to get it.

 

As to the DOF, that's exactly the point - you can increase the light hitting the sensor without having to work with shallower DOF than full frame.

Link to comment
Share on other sites

Where a focal reducer matches the FOV of the same FF lens when used on a Super-35 sensor area, since the focal length and FOV are identical, so are DOF and bokeh. The SB is actually a 1.1 crop, however the bokeh is close enough to call the same:

Link to comment
Share on other sites

Guest Ebrahim Saadawi

Would we expect the S35 crop to be as good as the full frame one? If so, yes speedboosting the s35 crop would be a fantasting idea. Extra stop of light for the already ridiculous lowlight.p That we're speaking of this shows how speedboosters really rendered fullframe sensors unimportant. When we're given the option we're actually deciding not to use the actual fullframe sensor and use the s35 one with speedbooster!

Link to comment
Share on other sites

??

 

Don't understand the bit about exposure - the point is that you get an extra stop of light and don't have to raise the ISO to get it.

 

You increase the light per area but not the total light energy, so Apsc+speed booster at iso 800 will have the same noise as full frame at iso 1600.   However as I said you may get a slight improvement in dynamic range since dynamic range is generally greater at lower iso's.

 


As to the DOF, that's exactly the point - you can increase the light hitting the sensor without having to work with shallower DOF than full frame.

 

Because most people talking about low light performance are talking about noise, and relating to my previous point: the exact same thing can be achieved by raising the ISO on full frame.  Same brightness, same noise.   It doesn't mean people cant do it though.  I will enjoy seeing how it works out.

Link to comment
Share on other sites

jcs is just pointing out an interesting feature/possibility.  the speedbooster is a really fascinating thing - pairing it with a sensitive camera is a natural idea.  By putting the camera into APS-C mode, the DOF becomes a bit bigger, but the speedbooster ups the amount of light.  So you don't get insanely shallow DOF but do get the extra stop. 

 

You get both. Your DOF with the speedbooster becomes full frame again, and you gain a stop on the lens. 

 

Using APSC mode and speedbooster speeds up your shot by a stop. Good plan!

Link to comment
Share on other sites

  • 3 weeks later...

So apparantly it does make sense to use the Speedbooster on the A7S in crop mode. Using the crop mode + speedbooster gives roughly the same field of view as the full frame mode but reduces the rolling shutter issue a lot. 

 

Link to comment
Share on other sites

  • Administrators

It's not quite the same field of view, more like 1.1x crop but yes, looking good.

 

Certainly an option if you want to reduce rolling shutter but optical performance in the corners will be better in full frame mode with no speed booster.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

 Share

×
×
  • Create New...