macro question

4

480sparky

Senior Member
If your camera's sensor measures 6.4 x 4.8 mm, then take a ruler and draw a 6.4 x 4.8 mm rectangle on a piece of paper. Can you get that rectangle to fill the frame? If so, then you're shooting at 1:1, or 1x.

Or if you have a ruler / tape measure with divisions at every 1mm, can you get close enough to image just 6+ mm? Same result.... you're at 1:1.

But I think you're getting stuck on the math. Yeah, it might be nice to know, but it's certainly not a requirement to either know, or post, the magnification.
 
W

WayneF

Senior Member
lucien said:
but with the math done, it's not a "true macro" then even at super macro. the ratio is .05 off am I correct is that because of the sensor size? Am I getting close. Can't everything be calculated then without asking these questions?

btw my math is for shit
Click to expand...

It's really not this hard. :) For 1:1, it does not matter what the sensor size is (however we do have to know digital sensor size to be able to measure the image size). For 1:1, it only matters that the image of the subject object on the sensor is the same size as the object... 1:1 is real life size. The sensor can be any size larger than the object image, we don't care. If we had a 3 inch sensor, and both the image size and the subject size were 5 mm, then that is 1:1, real life size.

The easiest way (knowing the sensor size) is to determine how much of a ruler will fit within that known sensor size.
 
L

lucien

Senior Member
DSCF0753.jpg
 
L

lucien

Senior Member
that's the best I can do. had to use a handy helper. Does this help at all? I could only get a little bit closer but by then the light is gone. And I'd be almost touching the object
 
Last edited:
W

WayneF

Senior Member
lucien said:
View attachment 151691
Click to expand...


This is around 37 mm view on a 6.4mm sensor. 37/6.4 is 5.78 times (image smaller than real life), which is 1:5.78 ratio. (about the same as the crop factor).
If this sensor size only showed 17 to 17.6, that would be about 1:1.
So not near 1:1, but is starting to approximate most usual "macro" photo work, like individual flowers, etc.
It is rather "close up".
 
L

lucien

Senior Member
so it "passes" kinda sorta, it's usable? So my earlier guesstimate of 1.5ish was very close:D

thank you
 
Last edited:
W

WayneF

Senior Member
I've never understood any of your "requirements" questions. I liken it to asking "Is $2.43 enough?". Enough for what? No clue here. I think there are no "requirements".

If it serves your purposes, then clearly it's good to go. It does what it does. It does a lot.

If you need more (magnification), then you need more. But probably not.


Perhaps where the question started is that the formal definiton of "macro" is magnification of image size to greater than life size, which is 1:1.

None of Nikons lenses can do more than 1:1, and as a result, what we call their macro lenses, Nikon labels them as micro lenses. Probably the last holdout honoring the older established terminology.

That does not trouble any of us. :) Few of us work at 1:1 often anyway.
 
W

WayneF

Senior Member
480sparky said:
OK, you've got roughly 4.2 cm showing in that image. Your camera, AFSAIK, has a 1.27 cm sensor. If my math is correct, 4.2 / 1.27 = ~1:3.3. Or, 0.3x.
Click to expand...

Math is OK, but the details are suspect.

I blundered at first too, but corrected it below:

Your 1.27 cm must be from a 1/2 sensor. But a 1/2 inch sensor is as compared to the old glass video tubes (which were larger than their effective area). The sensor area is not nearly that large. Totally obsolete measuring system now, but compacts still persist... sounds better than real life I suppose.

Wikipedia has Fuji 1/2 inch sensor as 6.4 mm wide.

Image sensor format - Wikipedia, the free encyclopedia
 
Last edited:
4

480sparky

Senior Member
WayneF said:
Math is OK, but the details are suspect.

Your 1.27 cm must be from a 1/2 sensor. But a 1/2 inch sensor is as compared to the old glass video tubes. The sensor area is not nearly that large. Totally obsolete measuring system now, but they still persist... sounds better than real life I suppose.

Wikipedia has Fuji 1/2 inch sensor as 6.4 mm wide.

Image sensor format - Wikipedia, the free encyclopedia
Click to expand...


I was going by what Fuji has on their website. I assumed that would be the most accurate since they make the cameras and Wikipedia doesn't.
 
W

WayneF

Senior Member
They do say 1/2" sensor, but it means as compared to an old glass video tube, round tube with rounded corners, which doesn't leave much room for the flat rectangular sensor area. The TV video cameras in the old days.

The Wikipedia link says:
[h=3]Table of sensor formats and sizes[/h] Sensor formats of digital cameras are mostly expressed in the non-standardized "inch" system as approximately 1.5 times the length of the diagonal of the sensor. This "optical format" measure goes back to the way image sizes of video cameras used until the late 1980s were expressed, referring to the outside diameter of the glass envelope of the video camera tube. David Pogue of The New York Times states that "the actual sensor size is much smaller than what the camera companies publish – about one-third smaller." For example, a camera advertising a 1/2.7" sensor does not have a sensor with a diagonal of 0.37"; instead, the diagonal is closer to 0.26". Instead of "formats", these sensor sizes are often called types, as in "1/2-inch-type CCD."



So it means 6.4 mm wide. All compact cameras do that. A Nikon Coolpix P340 and a Canon PowerShot S110 both say 1/1.7" sensor. That is 0.58 inches, but it means 7.6 mm wide... about 0.3 inch.

This is easily verified by the published crop factor.

Coolpix P340 says lens is "5.1-25.5 mm (angle of view equivalent to that of 24-120 mm lens in 35mm [135] format)"

Therefore 24/5.1 is crop factor 4.7

Wikipedia 1/1.7" diagonal says 9.5mm. 35mm film diagonal is 43.26 mm.
43.26 / 9.5 = 4.55 crop.

That as close as the details computed.

Widths of 36 / 6.4 is 5.625, which is closer, but crop normally uses the diagonal, because the frames are 4:3 and 3:2. Not same shape, and we are talking about equivalent field of view.

The Fuji HS25 says lens is
"f=4.2–126.0 mm, equivalent to 24–720 mm on a 35 mm camera"

So that is crop 24/4.2 = 5.71, so we could compute the sensor width (from 35mm film) as 36mm / 5.71 = 6.3 mm.

We only know rounded nominal data, but this is pretty close.

But there is no way to use 1/2" for anything (other than to look it up in the Wikipedia table). It is a meaningless number, a false way to represent digital sensors. :) It makes no sense, but they all do it. Probably because 1/2" sounds better than 6.4mm width or 9.5mm diagonal.

We could not care less now about old TV camera glass video tubes,
but computing crop factor and magnification still seems important.
We need exact sensor dimensions for that.
Thankfully, the larger cameras do this.
 
Last edited:
Top