Can you tell which photo is m4/3 or full-frame?

Started Sep 27, 2014 | Discussions thread
Randy Benter
Randy Benter Veteran Member • Posts: 3,197
Re: Nice application of Equivalence!
1

Jacques Cornell wrote:

Randy Benter wrote:

NCV wrote:

Randy Benter wrote:

NCV wrote:

Randy Benter wrote:

NCV wrote:

Randy Benter wrote:

NCV wrote:

Great Bustard wrote:

Lab D wrote:

Let's say you have a Canon 6D and a nice 50mm F1.4 lens, but you also wanted a nice 100mm lens. If you purchase an E-PM2 or E-M10 you get a Stabilized 100mm F2.8 lens. With m43 you can double the uses of your lenses.

Nice application of Equivalence, realizing that a 50 / 1.4 on mFT serves the same purpose as a 100 / 2.8 on FF.

Using Pretzel Logic it does. But using base (200 for example) quality on a FF sensor I need a 100mm 1.4 to match a 50mm 1.4 on M43 assuming the same shutter speed to have the same exposure. Depth of field will be different but who cares.

Why would you use base ISO on the FF if you are trying to achieve a certain shutter speed? If base ISO on m43 sensor is sufficient, then you can shoot the FF at 2-stops higher ISO without any increase in noise.

m43 50mm f/1.4 ISO200 1/125

FF 100mm f/2.8 ISO800 1/125

assuming the same shutter speed to have the same exposure. Depth of field will be the same, but who cares?

I already knew that. A jolly academic exercise that is of little interest in the real world.

If I am using a FF, why should I be interested at that time in the results on a smaller sensor. I am only interested in the degradation of the image on the sensor I am using.

This doesn't explain why you "need a 100mm 1.4 to match a 50mm 1.4 on M43".

We all know that at base ISO of for example 200 Aperture/shutter speed need to be the same across formats to get the same exposure.

This is just an academic exercise and is of little practical use. In the "real world", ISO is adjustable.

Let's say you are taking a portrait of a live subject using a m43 w/50mm 1.4 and you determine that 1/125 is the needed shutter speed. Then I hand you a FF w/100mm 2.8 and ask you to take the same shot with the same shutter speed. Are you saying you wouldn't be able to get the shot? If you did simply raise the ISO and take the shot, then how would the 2 shots differ? Would the FF shot be worse because you didn't have 1.4? If not, then why do you think you "need a 100mm 1.4 to match a 50mm 1.4 on M43"?

As I said, this is an just academic exercise and is of little practical use.

Call it what you will. You avoided the above questions, so I will answer them for you.

Q: If you did simply raise the ISO and take the shot, then how would the 2 shots differ?

A: They wouldn't be different, they would be very similar.

Q: Would the FF shot be worse because you didn't have 1.4?

A: No, It wouldn't be worse. It would be equal.

Q: If not, then why do you think you "need a 100mm 1.4 to match a 50mm 1.4 on M43"?

A: You don't need 100mm 1.4 to match a 50mm 1.4 on m43. If you used a 1.4 lens on both cameras, you would get a slower shutter speed, less DoF, and less noise on the FF camera, but none of those are needed.

Conclusion: The statement "I need a 100mm 1.4 to match a 50mm 1.4 on M43." is false.

I understood perfectly the first time.

But I can’t understand why I want to replicate the quality of M43 with my FF

I choose FF for a series of reasons and it is just unfortunate that I have to increase ISO to get a certain shutter speed DoF effect. I am just interested in getting a photograph of an acceptable quality, who cares if it equals the quality of a smaller format.

This is a very good point and it really is the crux of the issue. Your logic is understandable IF you start with the expectation that the FF camera should have roughly 2-stops better quality because it's full frame. If you want the FF camera to produce much less noise than the m43 camera, then you will need to use a 1.4 lens on the FF camera in order to achieve that, but that's not equivalence, that's superiority.

The way equivalence works is that you start with a given set of requirements for FoV, noise, DoF, etc., and then you can calculate the various combinations that will meet those requirements. As you said "[you are] just interested in getting a photograph of an acceptable quality" and that is very true, but first you need to establish what is "an acceptable quality" for you. If m43 at ISO200 meets my requirements for quality, then FF at ISO800 meets my requirements for quality. If I want to take a portrait with shallow depth of field, fast enough shutter speed to avoid blur, and an acceptable amount of noise I can use a m43 ISO200 50mm 1.4 OR a FF ISO800 100mm 2.8. If one of those meets my requirements, then so does the other. The FF camera will not be superior in this example, it will merely be equivalent.

Once I have established that EITHER a m43 w/50mm 1.4 OR a FF w/100m 2.8 will meet my given requirements, then I can compare the size, cost, and availability of those 2 options to determine which one best meets my needs. This, as I said before, is how I used equivalence to choose my m43 system.

This is my understanding as well. As long as apertures with the same DoF are available for both formats, the only advantage of FF is (possibly) more pixels. At very wide apertures, FF merely offers greater ability to trade away focus depth in exchange for more exposure. For example, by going from f2 to f1.4, FF can gain an additional stop faster shutter or lower ISO at the cost of shallower focus, but MFT lenses can't follow from f1.0 to f0.7 because they aren't available. This gives FF more flexibility in low light if you're willing to accept super-shallow focus, but if you need greater DoF, FF's ISO/shutter advantage pretty much evaporates. Since I often need MFT f2/FF f4 DoF in low light and I don't need more than 16MP, MFT serves me just as well as FF.

EXACTLY!!!! This is the same way that equivalence works for me IN THE REAL WORLD.

I find that I can get acceptable results with a wide variety of sensor sizes IF I am outdoors shooting in good light. When I go indoors or when the sun goes down, then a camera with a larger sensor begins to show it's strength. But, how large does the sensor need to be?

The answer will vary depending on the individual, how they shoot, and what level of quality they find acceptable. I commonly use a 35mm lens when indoors and I get acceptable results and ample DoF when shooting an APS-C camera at f/2.8. If I choose a larger aperture, then the DoF is too shallow to get 2 people in focus in the same shot. If I choose a smaller sensor at f/2.8, then the images will have too much noise. Using equivalence, I know that I can meet my personal standards with a m43 camera at f/2 (my E-M10 w/17mm) or an APS-C camera at f/2.8 (my X100S w/23mm). I can't meet my requirements with a 1" sensor (or smaller) because they don't make lenses fast enough to be equivalent. I could also meet my requirements with a FF camera at f/4 (RX1 w/35mm), but when I move to the next step after equivalence and compare the remaining differences, then the RX1 loses on price and the apertures faster than f/4 are beyond what I need. The RX1 would be perfect for someone else who begins with a different set of requirements.

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