[BrianR]

It isn't bizarre, it just may be a different way of phrasing it than you're used to. Class A said:

No. It's the same phrasing but different meaning. As expected, clarity ensues.

[philbaum]

I think the point is that if you are using an equivalent lens, for example, a 135 mm f2.8 and iso 200 on APS-C and a 200mm f4 and iso 400 on a full frame camera, the noise will be equivalent. The problem is just that there aren't fast enough lenses available for APS-C, particularly on the wide end of things.

That actually makes sense to me.

An FF sensor has a larger surface to collect light with, but unless you use a faster lens, the same total amount of light that would have hit the APS-C sensor has to be spread over the larger FF area. This reduces the light intensity, i.e. light per square mm, or in other words the exposure. ....

So higher looking ISO numbers on FF do not correspond to higher sensitivity, just like higher looking f-ratios do not correspond to less light gathering or more DOF. Using f/4 on FF achieves the same effect as f/2.8 on APS-C.

This does not make sense to me. For example:
A. If one is using a FF Pentax lens like the FA43, the light intensity across an APS sensor versus a FF sensor is the same. The only difference on an APS camera, the light falling outside the APS circle of the sensor is wasted.

B. If you go to this DXO page: Nikon D750 versus Nikon D7100 - Side by side camera comparison - DxOMark

The sports ISO rating for the FF camera is roughly 2.25 greater than the Nikon D7100 ISO rating. Then if you go back into the definitions of the Sports ISO rating, they talk about their ISO rating being a "performance" factor. So the D750 scores higher than the D7100, partially because its sports ISO rating is 2.25 times greater.

If you are correct in your statements, why does DXOmark consider higher ISO ratings of the FF to be a favorable factor??

I think its like Rondec stated, the noise level of the FF iso 450 is equivalent to the APS iso 200.

[jsherman999]

No. It's the same phrasing but different meaning. As expected, clarity ensues.

I honestly don't know what this ^ means.

[BrianR]

I honestly don't know what this ^ means.

Using "Faster" in a different way than usual as you described:

"50mm f/2.8 FF
35mm f/2.8 aps-c

They have the same exposure (light intensity), but the FF lens in this case is 'faster' because it actually is using a larger physical aperture: 50 / 2.8 = 17.8mm, vs 35 / 2.8 = 12.5mm"

Usually 'faster' refers to a straight comparison of the f-stop (relative aperture size), not the aperture size. Using the same words to mean something people aren't used to is just going to confuse everyone.

[jsherman999]

Using "Faster" in a different way than usual as you described:

"50mm f/2.8 FF
35mm f/2.8 aps-c

They have the same exposure (light intensity), but the FF lens in this case is 'faster' because it actually is using a larger physical aperture: 50 / 2.8 = 17.8mm, vs 35 / 2.8 = 12.5mm"

Usually 'faster' refers to a straight comparison of the f-stop (relative aperture size), not the aperture size. Using the same words to mean something people aren't used to is just going to confuse everyone.

Yes. IMO I think 'faster' should remain tied to 'f-stop', because that's what people are used to, but class A's underlying point was fully correct.

[Rondec]

If you pay attention though, 80% of the time equivalence has already been brought in to the discussion - and used incorrectly.

Nothing is more confusing (and potentially harmful to the wallet) than presenting it incorrectly.

.


Or the level of noise and DR they find acceptable.



Anyone who shoots an f/2.8 zoom a lot would disagree with you.

Or anyone who shoots any fast prime to squeak out the best SNR/DR available. That covers a lot of photography, and it's just a start

.

Interesting that you bring up dynamic range. My point is that the dynamic range and SNR are intimately linked to depth of field. You only get more, if you can manage to shoot the same iso on full frame that you do on APS-C. That means that you only get more in good light settings where you are already at low iso/high shutter speeds, places where you don't care if you get shallower depth of field, or places where you are stabilized and you don't care about your shutter speed at all. In two of these instances -- on a tripod or in really good light -- even if you can tell a difference pixel peeping, it is going to be close. A D800 has what, dynamic range of 14.5 at base iso compared to the 14.1 a K5 gets? Certainly that won't be visible in the real world.

So, it comes down to a simple question of depth of field. Can you live with less or not? The answer is sometimes yes and sometimes no, but it isn't clear cut.

[jsherman999]

Interesting that you bring up dynamic range. My point is that the dynamic range and SNR are intimately linked to depth of field. You only get more, if you can manage to shoot ...places where you don't care if you get shallower depth of field...
So, it comes down to a simple question of depth of field. Can you live with less or not? The answer is sometimes yes and sometimes no, but it isn't clear cut.

I think it's a mistake to frame this as "if can you live with less DOF" - implying it's a drawback you always have to overcome.

I think the majority of the time the shallower DOF either 1) doesn't matter (because of subject distance, etc) or 2) is a benefit to the image (subject isolation.)

So in other words the times you can't take advantage of the larger sensor's SNR/DR are not as frequent as the times you can. For some folks (like me) there's a big disparity - it's very rare that I 'have to' stop down to aps-c DOF.

[normhead]

This issue goes back and forth but it comes down to "do you use narrow DoF for subject isolation in portrait type images. For macro's and images where the camera is very close to the subject DoF is pretty much irrelevant. For portraits, where messy bokeh is an issue, FF gives you more flexibility. For landscape, going to a longer exposure and using high ISO is going to be pretty much equal on both systems.

The only folks that really worry me in this type of discussion are the ones that have their first post and they say "I bought my Pentax because I want those creamy out of focus backgrounds that APS-c gives you for portraits." , and you think "ut oh". He may be back in a couple years whining about his bokeh and longing for a full frame. I've seen a number of posts like that... what's guy to say?

I usually think well, if APS-c isn't good enough for him, he'll find out. Maybe really all he wants is what APS-c has to offer. But it is good to ask if they understand that the what they are asking for is not best served by APS-c, if he's looking for the ultimate narrow DoF image.

[Class A]

Usually 'faster' refers to a straight comparison of the f-stop (relative aperture size), not the aperture size.

And usually, it is fine to just refer to the f-stop, as you usually don't switch sensor sizes as well.

Using the same words to mean something people aren't used to is just going to confuse everyone.

Sorry, but f/2.8 on FF is faster than f/2.8 on APS-C (assuming equivalent focal lenghts).

You are essentially arguing to agree that
GBP 10 and
USD 10
refer to the same purchasing power, just because the numbers are the same.

F-ratios expressed in terms of different sensor sizes are like different currencies.

The meaning of "faster" is tied to DOF and exposure, not to a number that varies with the sensor size it is based on.

[Parallax]

or 2) is a benefit to the image (subject isolation.)

You mean like, ......... nah, too easy.

[jsherman999]

You mean like, ......... nah, too easy.

Eyeball isolation.

[Rondec]

I think it's a mistake to frame this as "if can you live with less DOF" - implying it's a drawback you always have to overcome.

I think the majority of the time the shallower DOF either 1) doesn't matter (because of subject distance, etc) or 2) is a benefit to the image (subject isolation.)

So in other words the times you can't take advantage of the larger sensor's SNR/DR are not as frequent as the times you can. For some folks (like me) there's a big disparity - it's very rare that I 'have to' stop down to aps-c DOF.

I'm sorry Jay, but here we come to an impass. The majority of photos that I shoot, I do with decent depth of field. Even when I take photos of my kids, I like to have some environment in play, rather than trying to blur it all away. I understand that you think that shallowness of depth of field is the goal of photography, but I differ somewhat. I shoot an awful lot of things where I attempt to have everything in focus. Sure, there are portraits of my kids or times when it is dark enough that I have to open up the aperture, but I have found that what makes a good photos is a combination of light, subject and composition, with the emphasis on light.

When I try to take photos of my kids and the light is really bad, even if I can shoot with maximally narrow depth of field, the photo still is so-so at best. It may contain a great memory and I may keep it, but it won't be something that anyone else appreciates. At the same time, if the light is good and I do a good job framing and capturing my subject, an in focus background will not be detrimental to the image created.

But the majority of photos that I take are landscapes and in those, I'm usually fighting to get maximal depth of field. I know that Nikon has a 14-24 f2.8 lens, but honestly, if I owned it and a D800, I would be shooting it at f10 most of the time.

[Class A]

This issue goes back and forth but it comes down to "do you use narrow DoF for subject isolation in portrait type images.

You can insinuate that all you want, it does not become true.

See, for example, the list of FF advantages, I posted earlier which is not comprehensive.

If you don't want/need an FF, that's fine.
If you think that FF only has one usage "shallow DOF portraits", that's fine too.
Even having a mental understanding of different sensor sizes that has no connection to reality is fine.

But please don't allege that all FF supporters are just after shallow DOF portraits and please don't confuse beginners with your notions of the consequences of different sensor sizes that just don't add up.

[jsherman999]

The meaning of "faster" is tied to DOF and exposure, not to a number that varies with the sensor size it is based on.

I hear you, but you'll have a tough time breaking it away from 'f-stop'. Here's a 1911 Encyclopaedia Brittanica excerpt:

..[Lenses] are also sometimes classified according to their rapidity, as expressed by their effective apertures, into extra rapid, with apertures larger than f/6; rapid, with apertures from f/6 to f/8; slow, with apertures less than f/11."

100+ years of nomenclature is hard to break from

I use 'physical aperture' or 'pupil diameter'. 'speed' can mean both f-stop and physical aperture, so it's perhaps best to not say 'speed' when you really do *not* mean f-stop. Just my opinion based on how much confusion I see around the term.

[Class A]

I know that Nikon has a 14-24 f2.8 lens, but honestly, if I owned it and a D800, I would be shooting it at f10 most of the time.

And you'd be getting better IQ than shooting with f/7 on APS-C (for the same framing).

If you don't need the extra IQ boost then you don't need FF gear, however, FF is not just for shallow DOF.

The large format shooters of yore, often stopped down to f/64. They didn't choose the heavy, large format equipment to get shallow DOF shots.