Camera resolution and photomacrography results.

Have questions about the equipment used for macro- or micro- photography? Post those questions in this forum.

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Larry45
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Camera resolution and photomacrography results.

Post by Larry45 »

Sirs:

I have been under the impression for several months that a low megapixel count camera was necessary because the higher count on the camera does not turn out good sharp images. I read it somewhere but can’t find it now.

I'm currently using a Canon 40D, 10 megapixels. I'm starting to have a little success using this camera. I own a Canon 7D, 18 megapixels. Would my using it change the results I obtain?

Regards,
Larry

JKT
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Post by JKT »

The pictures with high MP camera may not look as sharp when viewed at pixel level, but they will still contain more information. How much more depends on the resolution of you optics compared to the camera resolution.

If you scale them down to the low MP size, the picture should look sharper ... or at least not any worse. So you should not loose anything except processing time, but you may gain more details.

Scarodactyl
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Post by Scarodactyl »

I have a feeling a lot of this comes from sellers of expensive, low-mp cameras...

Larry45
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10 mp vs 18mp camera for photomacrography

Post by Larry45 »

Sirs:

I am using a 70's Pentax 200mm lens with a Nikon 10X objective mounted. Does this tell you anything? I think it is pretty good optics but I don't know any more to tell you. I suppose I should just try using the 7D.

Regards,
Larry

JKT
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Post by JKT »

I'd say give it a go. What can you loose?

As to the potential resolution, you didn't give the NA number of your microscope objective, which is essential in calculating the theoretical maximum resolution. The actual result could be worse, but not better.


If your NA is .30, I'd estimate maximum increase of around 10% in resolution. With NA .50 the same formula gives 18%. If the lens combination you have is not diffraction limited (= not as good as it theoretically could be) the increase will be less.

Disclaimer:
I can't remember where I got the approximate formula for combining optical and camera resolution. If that is off...

Macro_Cosmos
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Post by Macro_Cosmos »

Depends on the objective.
https://www.microscopyu.com/tutorials/m ... resolution

To account for camera-processing and debayering, times the number by 1.5 or 2. Generally, 36MP couple well with M Plan non-HR lenses from Mitutoyo.

If your lens can only resolve one pixel on a 20MP fullframe camera, splitting this pixel into 4 won't do much. You will get slightly more information, but it can be assumed it's marginal.

Pixel shift is a totally different matter however, but not many are willing to deal with the massive file sizes and longer workflow.

That's obviously not to say that high MP cameras are pointless if one's lenses can't take it. High MP usually means it's newer, has no OLPF, and has better ergonomics.

Larry45
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Joined: Wed Jan 16, 2019 6:42 am

Equipment Discussions

Post by Larry45 »

Sirs:

The NA of the Nikon objective is 0.25. Image

Regards,
Larry

JKT
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Post by JKT »

In that case you are not likely to see that much additional detail. 40D pixel size is your objective resolution / 1.9, whereas with 7D it is resolution / 2.6.

I understand there is no solid agreement whether you should have at least 2 pixels or 3, but the difference is likely not that big.

Anyway - what can you loose by trying? And remember to compare pictures only after they are scaled to same pixel size.

Ichthyophthirius
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Re: 10 mp vs 18mp camera for photomacrography

Post by Ichthyophthirius »

Larry45 wrote:I am using a 70's Pentax 200mm lens with a Nikon 10X objective mounted. Does this tell you anything?
Hi Larry,

You can download an EXEL spreadsheet on Charles Krebs' website for the calculations http://krebsmicro.com/relayDSLR/relayoptics1.html

You can add your NA (0.25), magnification (10x) and relay factor (1x; Nikon tube lens is 200 mm, just like your Pentax).

Depending on your criteria (2 ... 3.5 Pixel), the spreadsheet calculates 7.6 ... 23.3 MP required for an APS-C sensor.

You should give your 18 Mp camera a go!

Regards, Ichty

Larry45
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Joined: Wed Jan 16, 2019 6:42 am

Mitutoyo_M_Plan-Apo_20x_0.42_

Post by Larry45 »

Sirs:

What about the above? Will I see a difference using it with the 7D?

Regards,
Larry

Pau
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Re: Mitutoyo_M_Plan-Apo_20x_0.42_

Post by Pau »

Larry45 wrote:Sirs:

What about the above? Will I see a difference using it with the 7D?

Regards,
Larry
I think so.
Time ago I upgraded fom the 8Mpx 20D to the 7D and my pictures have more detail. Maybe they are not more sharp at pixel level but they contain more info.
Having both cameras at hand, why do not test them yourself?
Pau

ChrisR
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Post by ChrisR »

Yes, you will see it - all other things being equal.
IN contrast with normal photography, on a studio macro setup you can always use base ISO to reduce noise to a minimum, so that's not an issue..
Doubling your MP will only give you sqrt 2 = 1.4x the number of pixels on each axis remember, but if you look you see it.

That objective will cover much more than APS at 10x, so if you use an appropriate "tube" lens, say a 120mm, you effectively get a 6x, NA 0.25 setup. 10MP is nowhere near enough to do it justice.
Chris R

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