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Split-Image focusing - Is it possible?

  
 
Choderboy
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p.2 #1 · p.2 #1 · Split-Image focusing - Is it possible?


fjablo wrote:
Itís not a question of what you notice but whether the introduced lag (that you may or may not notice) impacts how quickly you adjusted focus. And whether thatís a total of 250ms or 275ms is largely irrelevant. And esp whether a digital split screen takes that to 280ms or not doesnít matter at all.

And yes thatís simplified. So is your description of the EVF feed above


So please elaborate n the feed to EVF.
Notice I said "This is how I thought it worked"
ie, I did not claim to know.
The obvious conclusion to your statement is that you do know.
So are you just going to feel smug about knowing and keep it to yourself?



Sep 22, 2022 at 06:06 AM
DaveFP
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p.2 #2 · p.2 #2 · Split-Image focusing - Is it possible?


Choderboy wrote:
Here's how I thought it worked:

The EVF or LCD is displaying a JPG.

It can't be a straight feed as the 24, 36, 42, 50 or 61 megapixels of the sensor won't fit in the 1 - 3 megapixel EVF or LCD.

Remember, the A1s EVF has 9.9 million dots. 3.3 million red, 3.3 million green and 3.3 million blue.
So using the same terminology used for the sensor, the EVF is 3.3MP.
The A1 LCD has only 1.44 million dots, or 0.48MP.

Also, the sensor outputs RAW data. This needs to be processed before it gets to the EVF or LCD.
Evidence of this is
...Show more

"Straight feed" was not to imply that there is a simple wire connecting the two.

Of course the data streaming off the sensor has to be processed in order to provide a interpretable image in the EVF.

I was suggesting that the additional processing could be slow.

Perhaps not.

In any case, as pointed out above, it would not be a big deal as you would only activate the feature for static imaging.

"relatively straight feed" might have better conveyed my thoughts.




Sep 22, 2022 at 06:09 AM
Choderboy
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p.2 #3 · p.2 #3 · Split-Image focusing - Is it possible?


DaveFP wrote:
"Straight feed" was not to imply that there is a simple wire connecting the two.

Of course the data streaming off the sensor has to be processed in order to provide a interpretable image in the EVF.

I was suggesting that the additional processing could be slow.

Perhaps not.

In any case, as pointed out above, it would not be a big deal as you would only activate the feature for static imaging.

"relatively straight feed" might have better conveyed my thoughts.



Cool. I have seen various phrasing used in articles, basically saying very close to 'straight feed' but thought it was a clunky way of differentiating mirrorless from the optical path used in a DSLR.
I think the processing is quite fast, it's the reading the sensor which is slow which is why stacked sensors have such an advantage (assuming the advantage is an advantage the user wants)





Sep 22, 2022 at 06:22 AM
Choderboy
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p.2 #4 · p.2 #4 · Split-Image focusing - Is it possible?


Like some others in this thread, I tried the split focus feature on Fuji (the X100s) but just did not think much of it. Focus peaking seems better and I do like the MF assist arrows feature of the EOS-R.


Sep 22, 2022 at 06:25 AM
fjablo
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p.2 #5 · p.2 #5 · Split-Image focusing - Is it possible?


Choderboy wrote:
So please elaborate n the feed to EVF.
Notice I said "This is how I thought it worked"
ie, I did not claim to know.
The obvious conclusion to your statement is that you do know.
So are you just going to feel smug about knowing and keep it to yourself?


Oh I don't know all the technical details either, but there is more to it than:
- RAW conversion to JPG
- Picture style setting
- Downsizing


- It's not really JPG compression, but some sort of video codec but fair enough
- RAW conversion and picture style setting are pretty much the same, unless you meant demosaicing only, but then the JPG doesn't make sense in the first step.
- There might be some downsizing at the end, but most of the time the EVF feed will not be based on the full sensor to begin with but will involve lots of line-skipping to speed up the process.

Not saying how you described it was necessarily wrong. Just that it's a simplified view of that whole process.

Manual focus assists are an extra processing step in that chain, e.g. for focus peaking the converted image must be read out to highlight pixels with a certain contrast threshold to surrounding pixels.

I assume Fuji's digital split image uses data from the phase detection pixels that the camera analyses "anyway" for autofocus.

But: the added lag of these steps won't noticeably impact how quickly you can or cannot manually focus on e.g. a moving subject and that was actually my main point --> the discussion should be about what is or could be an effective focusing aid (imo Canon focus guide > Nikon changing color of AF point > focus peaking) and not about potential downsides of a little bit of extra processing



Sep 22, 2022 at 07:03 AM
Erichimedes
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p.2 #6 · p.2 #6 · Split-Image focusing - Is it possible?


Sony's Achilles's heel is lack of firmware features, imho. I don't understand why we can't use their excellent autofocus processing systems for manual focus. Just a small spot that you can move around the frame that turns red or green when that spot is in focus. Bonus points for if that spot can be made to move around on it's own and detect things like eyes, etc.

I suppose this is available in Canon mirrorless cameras now. Hmmm...



Sep 22, 2022 at 09:33 AM
johnvanr
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p.2 #7 · p.2 #7 · Split-Image focusing - Is it possible?


To me, itís the micro prism of those old cameras that made more of a difference than the split image.


Sep 22, 2022 at 09:38 AM
osv2
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p.2 #8 · p.2 #8 · Split-Image focusing - Is it possible?


Erichimedes wrote:
Sony's Achilles's heel is lack of firmware features, imho.


that indicates an abject lack of knowledge about sony cameras.

Erichimedes wrote:
I don't understand why we can't use their excellent autofocus processing systems for manual focus.


because autofocus is not manual focus.

that's why god invented magnification+peaking for manual focus.

Erichimedes wrote:
Just a small spot that you can move around the frame that turns red or green when that spot is in focus.


see above, and the video below.

Erichimedes wrote:
I suppose this is available in Canon mirrorless cameras now. Hmmm...


i think it's more like you are confusing several different concepts.

magnification+peaking is far more accurate than any split-screen function that can't do magnification... here is how it's done circa 2014, be sure and set the peaking at minimum for the best accuracy.







Sep 22, 2022 at 11:09 AM
 


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osv2
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p.2 #9 · p.2 #9 · Split-Image focusing - Is it possible?


Choderboy wrote:
Googling Tyler Durden, I just proved my own point. I watched Fight Club about a week ago and I did notice at least 2 of the 4 times a single frame of him was inserted into the movie before he was introduced. I did not think much of it at the time, but "tyler durden 1 frame" google let me in on the story. They did not cut to a different scene either, he just appeared in the scene for a single frame.


that tells you nothing about how quickly you reacted to seeing the inserted frame, which is the subject being discussed in a conversation about lag.




Sep 22, 2022 at 11:19 AM
Erichimedes
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p.2 #10 · p.2 #10 · Split-Image focusing - Is it possible?


As I've been using primarily manual focus lenses on Sony cameras for the past 2 years, I can say I'm somewhat acquainted with magnification and focus peaking, but I watched your video anyway hoping there was a point buried in there somewhere.

To see what I'm talking about, go ahead and follow this link. Canon now calls it "focus guide" and it's different than peaking. If you'd ever used manual focus lenses with Canon SLRs you might be familiar with it. Canon now calls it "focus guide" and it's different than peaking:
https://snapshot.canon-asia.com/article/eng/focus-guide-mf-peaking-making-manual-focus-easier

I'm not saying this would somehow be more accurate, although it might be. But it would be nice to have this feature that we could turn on or off, as an alternative to focus peaking when we want to pull focus and compose at the same time, which you cannot do when in magnified view.

Options, you know? We all like having options.


osv2 wrote:
that indicates an abject lack of knowledge about sony cameras.

because autofocus is not manual focus.

that's why god invented magnification+peaking for manual focus.

see above, and the video below.

i think it's more like you are confusing several different concepts.

magnification+peaking is far more accurate than any split-screen function that can't do magnification... here is how it's done circa 2014, be sure and set the peaking at minimum for the best accuracy.






Sep 22, 2022 at 06:27 PM
osv2
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p.2 #11 · p.2 #11 · Split-Image focusing - Is it possible?


Erichimedes wrote:
To see what I'm talking about, go ahead and follow this link. Canon now calls it "focus guide" and it's different than peaking. If you'd ever used manual focus lenses with Canon SLRs you might be familiar with it.


the fact that it's used on dslrs tells us all that we need to know :-0

Erichimedes wrote:
I'm not saying this would somehow be more accurate, although it might be.


i don't see how, given that it doesn't work with magnification.

it's based in part on af distance info, which is not accurate with any camera... go down to home depot and see if you can find any dpaf distance measuring tools, afaik it's all laser-based.

Erichimedes wrote:
But it would be nice to have this feature that we could turn on or off, as an alternative to focus peaking when we want to pull focus and compose at the same time, which you cannot do when in magnified view.


true, you can't easily change framing on the shot when magnified, but making the mag window smaller in the evf makes it less accurate.

we all want an mf tool that's useful for sports and moving objects, beyond what peaking can do, in part because sony does not give us enough control over the peaking level to make it fully useful.



Sep 22, 2022 at 07:47 PM
Grenache
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p.2 #12 · p.2 #12 · Split-Image focusing - Is it possible?


Hopefully obvious, but in order for magnification to work, your viewfinder diopter must be set to match your vision. If it is off even a bit, it will be impossible to get sharp focuse where you want it. Having shot with various prisms on manual cameras, the ability to magnify is way more useful than any prism or ground glass type ever was.


Sep 22, 2022 at 09:06 PM
osv2
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p.2 #13 · p.2 #13 · Split-Image focusing - Is it possible?


i had a crappy k10d that i tried to change focusing screens on, in order to get that split-screen focusing.

unfortunately the distance to the mirror was slightly off, and even after shimming it i still couldn't get accurate manual focus even on stationary objects... plus, the camera had no live view capability.

so the a7r in 2013 was a real slice of manual focus heaven i hate dslrs.



Sep 22, 2022 at 09:48 PM
DaveFP
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p.2 #14 · p.2 #14 · Split-Image focusing - Is it possible?


Fact is many old SLRs had split prisms within their fresnel/matte screens.

The split prism was for action; the fresnel for critical focus.

I generally found the split prism to be easier; even when I had young eyes.

A lot of people don't like peaking but I find it very useful when set properly.

Certainly faster than magnifying to find the shimmer (while not intrinsically as accurate).



Sep 22, 2022 at 10:24 PM
AmbientMike
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p.2 #15 · p.2 #15 · Split-Image focusing - Is it possible?




Minatureman13 wrote:
I find split-image focusing (like in the old SLRs) so much faster then anything available to me on my A7r3. I've tried MF Assist and Peaking, but neither of those are as easy as using an a split-image or microprism.

I'm wondering if its possible to incorporate a split-image or microprism into a mirrorless camera?

This is what I'm talking about:

https://www.cameratim.com/photography/about-photography/images/chinon-ce-4-manual-focussing.jpg


I'm not sure why those disappeared. Definitely nice to have.

I got inexpensive ones from China for 40D and 5D 2010 or so. Not sure if anythings available now. Katzeye used to make them



Sep 23, 2022 at 03:55 PM
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