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sensor displacement in casing

danlindberg

Well-known member
I want to calibrate my Leica distometre for accurate readings and when I 'hook' the D5 onto the back of the Alpa MAX, I am not exactly at the sensor level.

Looking at the back, there are a couple of mm distance before the protective glas, and then tilting it back and forth to see the underlaying sensor I estimate another 3-4mm to the actual sensor.

Since I cannot measure that distance myself, maybe this is known somewhere and can post a precise number?

Thanks!

Oh, it is ofcourse my Aptus II 5 I'm talking about....
 

Shashin

Well-known member
For which mount? You should be to get the flange distance for the back for the specific mount.

But unless you are doing macrophotography using the D5 to measure, do you really need to be that precise?
 

dougpeterson

Workshop Member
At that level of macro it might be better to use live view than direct measurement. Can your application/workflow sustain a laptop or your budget an upgrade to a Credo?
 

danlindberg

Well-known member
I suppose you are right :eek: In my case a laptop would be the solution for those images.

But anyway, you wouldn't happen to know how many mm the sensor sits behind the protective glas? :)
 

Shashin

Well-known member
Focus your lens to a known distance and then use the D5 to figure out what position it needs to be in order to read that distance. You don't need the flange distance.
 

danlindberg

Well-known member
Yes, what I'll do tomorrow is focus with live view into a wall and then measure with the D5. The difference between D5 reading and what the lens says is the distance I am looking for. :D
 

gazwas

Active member
Dan, do you measure distance with the Disto on every shot you take?

I was thinking of getting a D5 for use with my new camera but have been thinking guesstimation and hyperfocal was a better method. Do you find you need more accuracy than hyperfocal?
 

danlindberg

Well-known member
Gazwas, I use both guesstimation, hyper and D5. Method depends on which lens I use, at what distance, what f-stop and how the scene looks. Open landscapes with the 35 XL the D5 never leaves the bag, but on the other hand if I'm in the woods and setup the Max, lets say, around 2 metres distance from a trunk. Then I really benefit from knowing if it is 1.91 or 2.32 to that trunk. At that distance it makes a difference to be correct even with the 35 XL.
With longer lenses this is further enhanced, but having said that, I am surprised at how well hyperfocal and guesstimation actually works in many situations.

Another example. My latest interior shots have been made exclusively with the SK 28 XL, most of them with f8 and most of them with the focusingring between 1.5-4 metres. If I go in 100% I can quite easily see where the focus is set. This means I would not dream of not using the D5 so that I can really pinpoint focus on 'the vase on the table' or 'the sculpture to the right'.....

I for one would feel very limited and not satisfied without the D5, especially on assignments. But a 35 XL and an Alpa TC over my shoulder taking a walk along the beach, then guesstimation will do nicely.
 

dchew

Well-known member
Dan,
I will be curious what you get. I tried various ways to measure the distance from the back edge of the STC body to the sensor surface, since I flip the D5 foot down and hold it up against the camera on either the top or port side. The offset I have programmed into my D5 is 0.02 ft, or 6 mm. I actually think it is somewhere between 6-9 mm, or 0.02-0.03 ft.

But I have an IQ sensor.

Dave
 

gazwas

Active member
From reading many posts about tech cameras, the getdpi laser measure of choice appears to be the Leica Disto D5.

Can someone please explain what does the D5 do over the entry level D210 as the specs say they measure to the same accuracy. The only obvious feature I could see different was the video pointer which seems useful outside when measuring objects at distance but of little real world use as at greater distance hyper focal focus removes the need for "to the centimetre" readings doesn't it?
 

dchew

Well-known member
Gareth,
It is indeed the video that makes it the preferred model. In my head getting an accurate measurement matters up to about 50 ft, although I admit I haven't run the distance vs. "my" hyper focal settings through the appropriate calculations. There have been times when I could not see the laser in the 20-50 ft range due to light conditions or whatever.

The distance estimates in my head are pretty shaky in that 20-50 foot range, so for me it really helps. The way it works you turn on the unit and the video is not turned on. You have to purposefully turn it on by pushing a button. So I usually try it without the video first. Point of that being I have a pretty good idea of how often I need that feature to get a good reading. About 20-30% of the time I need to turn on the video because I cannot see the red dot.

I used to carry an off-brand distance meter. Frustrated the heck out of me and I gave it to a friend for non-photography applications.

Dave
 
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gazwas

Active member
The way it works you turn on the unit and the video is not turned on. You have to purposefully turn it on by pushing a button. So I usually try it without the video first. Point of that being I have a pretty good idea of how often I need that feature to get a good reading. About 20-30% of the time I need to turn on the video to get the reading.
What is it that stops you getting the reading with just the laser pointer, ambient light and not seeing the red dot or does the video pointer measure differently?
 

danlindberg

Well-known member
Dan,
I will be curious what you get. I tried various ways to measure the distance from the back edge of the STC body to the sensor surface...

Dave
It was tougher than I thought. I have tried many times now and it seems to be very accurate if I add 5mm to the D5.

What is it that stops you getting the reading with just the laser pointer, ambient light and not seeing the red dot or does the video pointer measure differently?
You simply cannot see the red dot many times! With the video it is game on...
 
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danlindberg

Well-known member
On a direct question to Alpa, I received this drawing within 4 hours. Thank you Alpa! Amazing service :thumbs:

 

dchew

Well-known member
That's awesome Dan, thank you! Plus, I feel so smart with my 6-9mm measurement. No I mean estimate. :)

Dave
 

Guy Mancuso

Administrator, Instructor
I've gone back and forth on the D5 now on keep it or take it out and I always seem to come back to focus mask than 100 percent viewing with a 3x Hoodman lupe. Worst case I'll use live view but I just don't use the D5 anymore. I guess here is where a IQ makes the difference since I'm pretty confident I nailed it with those techniques. But sometimes I admit it's nice to know a starting point instead of hmmm looks like 15ft
 

gerald.d

Well-known member
When this kind of level of focusing accuracy is required, what are people's workflows when it comes to measuring distance to an object that is off-axis?

i.e. if the object you want to focus on is not dead-center in your composed FoV, you can't simply measure the distance with a laser and then dial that in on the lens. So what do you do?
 

danlindberg

Well-known member
I've gone back and forth on the D5 now on keep it or take it out and I always seem to come back to focus mask than 100 percent viewing with a 3x Hoodman lupe. Worst case I'll use live view but I just don't use the D5 anymore. I guess here is where a IQ makes the difference since I'm pretty confident I nailed it with those techniques. But sometimes I admit it's nice to know a starting point instead of hmmm looks like 15ft
With an IQ or Credo, I would most probably think the same. But with the Aptus, I could not live without it.

When this kind of level of focusing accuracy is required, what are people's workflows when it comes to measuring distance to an object that is off-axis?

i.e. if the object you want to focus on is not dead-center in your composed FoV, you can't simply measure the distance with a laser and then dial that in on the lens. So what do you do?
I see what you are saying here, and in most cases the 7mm extra from the D5 readout is ofcourse just a non-issue. Don't get me wrong here, I am not at all after a few mm precision for readings of 5-10-40 metres, or off-axis readings either. It is in the very close range of the lenses it matters.

I can illustrate it with this snapshot of the HPF ring. Setting up the camera at these short distances and shooting a completely flat surface - then those 7mm "does matter". Check how close the different distence settings are....

 
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