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Crop factor affects maximum F/stop?
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May 4, 2021 12:17:38   #
User ID
 
larryepage wrote:
Like many who write for a living, especially today, Tony Northrup is an "opinion as fact" person. He is also a "snapshooter," with what appears to be pretty limited artistic vision. Those who fixate on what he says seem to tend toward becoming the same sort of phototechnologist that he is. That would be less of a problem if he demonstrated a deeper knowledge of the things he likes to write about.

The truth is that given the state of photographic technology today, while some of this is interesting to talk about (for a while), most of it combined has less than a 5% impact on the actual impact of most photography displayed on this site. Fixing all of the technical problems in most photographs here still will not fix the lack of interest and viewability that some additional care with subject selection, composition, and presentation (post processing) choices will fix. Let's face it...the worst of what is available from the major makers is really still pretty serviceable.

The same attitude comes up every time there is a post asking how to design, say, exposure triangle drudgery for a son or daughter who wants to learn photography. Forget that. It will come. Talk about seeing, and capturing what you see. That's what viewers care about. Not f/stops and depth of field that have been discussed to the depth of the field.
Like many who write for a living, especially toda... (show quote)


Amen. You nailed it.

Not just nailed but riveted, screwed down, and welded it.

I am toadally unimpressed that users can reliably consistently post endlessly boring, nearly identical, BIFs perfectly focused exactly on the eye.

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May 4, 2021 14:20:49   #
wdross Loc: Castle Rock, Colorado
 
larryepage wrote:
Like many who write for a living, especially today, Tony Northrup is an "opinion as fact" person. He is also a "snapshooter," with what appears to be pretty limited artistic vision. Those who fixate on what he says seem to tend toward becoming the same sort of phototechnologist that he is. That would be less of a problem if he demonstrated a deeper knowledge of the things he likes to write about.

The truth is that given the state of photographic technology today, while some of this is interesting to talk about (for a while), most of it combined has less than a 5% impact on the actual impact of most photography displayed on this site. Fixing all of the technical problems in most photographs here still will not fix the lack of interest and viewability that some additional care with subject selection, composition, and presentation (post processing) choices will fix. Let's face it...the worst of what is available from the major makers is really still pretty serviceable.

The same attitude comes up every time there is a post asking how to design, say, exposure triangle drudgery for a son or daughter who wants to learn photography. Forget that. It will come. Talk about seeing, and capturing what you see. That's what viewers care about. Not f/stops and depth of field that have been discussed to the depth of the field.
Like many who write for a living, especially toda... (show quote)


Well said. Hopefully some will read and discern what is "wheat" and what is "chafe".

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May 4, 2021 14:24:31   #
Jahmoe
 
Wallen wrote:
LOL

Imagine a room with 50 people, we call that full frame.
Imagine another room only half the size and contain the same amount of people. That is our APS-C

The other room being only half the size, if we compare size for size equality, our full frame room only has 25 persons in it while the APS-C has 50.

If i deliver one pizza to an equal room size basis, then 1 pizza get to be shared with 25 people in the fullroom and 50 people in the APS-C.

That is what happen to light going on a lens. It's the same f-stop. Same pizza. Same amount of light, but it is being shared by a lot more pixel. So the pixels receive a smaller amount of light, same as the small room where each person gets a smaller slice of pizza.

That amount to an exposure equivalent that is more noisy compared to the full frame. Specially in lower light conditions.

How do we get the same quality? More light. So any full frame setting needs to be set 1 stop lower for the APS-C to have the same image quality.
We'll we cant have more light because we take a picture of the same event with 2 different cameras.
So we end up with the APS-C having a "practical" equivalent of a higher f-stop number.
LOL br br Imagine a room with 50 people, we call ... (show quote)


Professor,
Thanks very much for the above explanation. Coming from an engineering background and studying Light in college that's the best explanation I've ever heard or read.

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May 4, 2021 14:28:51   #
jrm21
 
deleted.

I didn't make it through all the pages prior to posting. Others confirmed what I thought and explained it better than me.

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May 4, 2021 18:41:00   #
lamiaceae Loc: San Luis Obispo County, CA
 
selmslie wrote:
You have not learned from your experience.

Take a look at how the Exposure value. You will see that the film/sensor format does not enter into the calculation. It's the same for a smartphone as it is for a large format camera.

You are confusing exposure with the effect of format on DOF. You can thank Tony Northrup for leading you and many others astray.


Has Tony ever worked with a 4x5 view camera?

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May 4, 2021 19:00:31   #
TonyBot
 
lamiaceae wrote:
Has Tony ever worked with a 4x5 view camera?


This 'Tony' has -

... Way back when ... 4x5 was considered a "miniature" format - especially in the furniture industry. 8x10s ruled, and a 300mm or longer lens was most common, with an ƒ6.3 or ƒ8.0 usually used, stopped down to ƒ64.

(and then, 6.3 was the same, whatever focal length was used. Along with several dozen "hot" lights, "spray and pray" meant you might have taken two to three dozen shots in a 10 hour day!)

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May 4, 2021 20:01:28   #
selmslie Loc: Fernandina Beach, FL, USA
 
lamiaceae wrote:
Has Tony ever worked with a 4x5 view camera?

Probably not. If he had he would not have made some of the sophomoric claims that have made him infamous.

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May 5, 2021 07:19:08   #
BebuLamar
 
selmslie wrote:
An older macro lens does indeed change the effective aperture as you focus closer (or add extension tubes) because the aperture moves further from the sensor or film plane. My 105mm Lester Dine macro behaves this way as did the 55m Micro Nikkor. I'm not sure about the 60mm Micro Nikkor that I no longer own.

But a newer macro lens, even if it's not designated as IF (internal focus) can behave differently.

My 60mm AF 2.8D Micro Nikkor will maintain the specified aperture from infinity to 1:1 between f/5 and f/32, the normal range I would use for macro photography,.

But from f/2.8 to f/5 the effective aperture adjusts as the focus distance changes. In other words, I can set it to f/2.8 when focused at infinity but the aperture changes as I focus closer until at 1:1 it shows f/5.
An older macro lens does indeed change the effecti... (show quote)


So the lens does goes down from f/2.8 to f/5 which is a little bit less than an old macro lens. If you set the the aperture from f/5 and up the camera automatically open up the aperture to compensate so you get f/5 at all distances.

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May 5, 2021 07:28:17   #
selmslie Loc: Fernandina Beach, FL, USA
 
BebuLamar wrote:
So the lens does goes down from f/2.8 to f/5 which is a little bit less than an old macro lens. If you set the the aperture from f/5 and up the camera automatically open up the aperture to compensate so you get f/5 at all distances.

The main benefit is that you don’t need to do the side calculation to adjust the exposure if you are using an external meter or flash/artificial light.

On the other hand, who bothers with that for digital when you can just take a shot and immediately see the results?

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May 5, 2021 13:56:59   #
petrochemist Loc: UK
 
BebuLamar wrote:
So the lens does goes down from f/2.8 to f/5 which is a little bit less than an old macro lens. If you set the the aperture from f/5 and up the camera automatically open up the aperture to compensate so you get f/5 at all distances.


Not if you're going for higher magnifications, even a f/2.8 lens can't reach an effective f/5 if extended enough for twice life size.

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May 5, 2021 14:02:58   #
selmslie Loc: Fernandina Beach, FL, USA
 
petrochemist wrote:
Not if you're going for higher magnifications, even a f/2.8 lens can't reach an effective f/5 if extended enough for twice life size.

It can if it's actually f/2.5 wide open.

It's easier to sell it as an "f/2.8" lens if they don't have to explain this to the consumer.

How many lenses out there are exactly f/1.8 rather than something slightly different wide open? Probably most of them.

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May 5, 2021 16:27:47   #
petrochemist Loc: UK
 
selmslie wrote:
It can if it's actually f/2.5 wide open.

It's easier to sell it as an "f/2.8" lens if they don't have to explain this to the consumer.

How many lenses out there are exactly f/1.8 rather than something slightly different wide open? Probably most of them.


Yes if it was f/2.5 it would JUST at 2x (but not at 2.1x let alone 5x so even there my point stands).
A f/2.5 sold as f/2.8 would require a marketing department to round down, it's far more common for them to make specs look better if at all possible.

Canon make a 50mm f/2.5 macro lens (see https://www.amazon.co.uk/Canon-50mm-Compact-Macro-Lens/dp/B00006I53V ) They don't try to sell it as a f/2.8 as they know the smaller the f number the better it looks in the specs.

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May 5, 2021 16:44:52   #
BebuLamar
 
petrochemist wrote:
Not if you're going for higher magnifications, even a f/2.8 lens can't reach an effective f/5 if extended enough for twice life size.


Twice life size would require extension tube. The lens can only do life size.

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May 5, 2021 17:00:44   #
selmslie Loc: Fernandina Beach, FL, USA
 
petrochemist wrote:
Yes if it was f/2.5 it would JUST at 2x (but not at 2.1x let alone 5x so even there my point stands). ...

It's actually more complicated than that.

As I'm sure you are aware, only f/2, 4, 8, 16, etc are real values. What we call f/2.8 is actually f/2.828427125 and f/2.5 is actually f/2.5198421, etc. One stop increments are separated by a ratio equal to the square root of 2 (1.414213562) and 1/3 stop increments by a ratio of the sixth root of 2 (1.122462048). The in-between f-stops are simply numbered with values that are easy to remember like 4, 4.5. 5, 5.6, 6.5, 7.1, 8, etc

But it gets even worse. As it is implemented in a lens the numbers don't actually work out as being precisely and equally spaced, just close enough for photographic use.

I measured the raw values for f/2.8 through f/5.6 with the lens on a Df and the focus at infinity and ended up with increments of 0.1656, 0.2897, 0.3337, 0.3397, 0.3847, 0.3798 stops. The spacing should have been 0.3333 stops in all cases. The spacing between f/2.8 and f/3.2 is about half what we might expect,

Then I measured the raw values for f/5 through f/11 with the focus at 1:1 and ended up with increments of 0.0871, 0.4061, 0.2783, 0.2240, 0.3396, 0.4335, 0.2003 stops. It's still not 0.3333 stops for each step and we know that Nikon is doing something peculiar at macro distances. The difference from f/5 to f/5.6 of 0.0871 shows that f/5 is actually a lot closer to f/5.6 (maybe f/5.5) but the camera is not reporting the actual value.

The results will surely be different with other newer macro lenses but probably not for the older ones where the internal adjustments are not taking place.

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May 5, 2021 18:42:05   #
petrochemist Loc: UK
 
BebuLamar wrote:
Twice life size would require extension tube. The lens can only do life size.


The unaided lens can only manage lifesize, but so what? Your claim was 'at any distance' and double or triple lifesize is hardly extreme macro. By historical usage macro is lifesize & greater to about 10x lifesize, extension or other tricks are needed to get beyond the lowest boundary of macro - these closer distances are part & parcel of true macro.

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