[jsherman999]

I agree. It's only the equivalency police who insist on saying that you must compare f2.8 lenses on APS-C with f4 lenses on full frame. .

I would say it's the folks who try to come to some erroneous conclusion by comparing f/2.8 zooms on FF vs. aps-c.

They can benefit from some clarity, even if they don't really want clarity.

[Class A]

LumoLabs -- True reasons for Full Frame -- Whitepaper

A few points that can be gained from the article:

• an FF sensor does not provide shallower DOF per se, but FF lenses offer more options, about a 1 stop advantage in practice (for which one has to pay in terms of weight, size, and purchase price, however only if one wants to; equivalent FF lenses meed not be more expensive, heavier or bigger).
• an FF sensor (using the same sensor technology) will have higher dynamic range but not better low-light performance. The latter can only be gained by using better lenses (see above).
• the same AF system will perform much better with an FF camera (as the tolerances required for the same sharpness are much looser).
• from a certain level of image quality upwards, an FF system is cheaper, and some level of IQ is only achievable with an FF system (because equivalent APS-C equipment does not exist). For lower image quality, smaller sensor systems are cheaper.

I look forward to the FF model because if I want to take the same images as before, I'll use longer lenses stopped down more (better IQ) and if I want to take images with shallower DOF, I can because I already have the respective FF lenses that have no counterparts on APS-C with which I could take the same images.

Also, and rather importantly, AF errors and lens faults (both are practically always present to some extent) will matter much less, due to the smaller enlargement factor required for FF.

For those who do not believe the physics (falconeye, the author of the above linked article, is a physicist and really knows what he is talking about) I would suggest to visit the "Some Full-frame shots & thoughts" thread. The difference between good FF shots and good APS-C shots is clear as night and day to me. For anyone who does not see a difference, they don't need an FF.

[DavidSKAF3]

if I want to take images with shallower DOF, I can because I already have the respective FF lenses that have no counterparts on APS-C with which I could take the same...

Which lenses are they?


Thank You,


Dave

[Rondec]

Which lenses are they?


Thank You,


Dave

There aren't APS-C equivalents to a lot of full frame lenses -- all of the FA limiteds, the FA 50 f1.4 (or even the DA 50 f1.8).

[philbaum]

LumoLabs -- True reasons for Full Frame -- Whitepaper

A few points that can be gained from the article:[LIST][*] an FF sensor (using the same sensor technology) will have higher dynamic range but not better low-light performance. The latter can only be gained by using better lenses (see above).
.

I don't understand the above item on your list. ISO performance is a measure of the sensitivity of a sensor to light. The greater the sensitivity, the better a sensor responds in low light conditions.

To find an equivalent ISO in crop cameras, the square of the crop factor has to be applied to the iso level.

So for a full frame camera, the usage of 800 iso would require 2.25x800=1800 iso on an aps camera and 4X800 or 3200 on a m4/3 camera. The larger sensor is more sensitive to light - a great feature in my opinion.

[Rondec]

I don't understand the above item on your list. ISO performance is a measure of the sensitivity of a sensor to light. The greater the sensitivity, the better a sensor responds in low light conditions.

To find an equivalent ISO in crop cameras, the square of the crop factor has to be applied to the iso level.

So for a full frame camera, the usage of 800 iso would require 2.25x800=1800 iso on an aps camera and 4X800 or 3200 on a m4/3 camera. The larger sensor is more sensitive to light - a great feature in my opinion.

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.

[Class A]

So for a full frame camera, the usage of 800 iso would require 2.25x800=1800 iso on an aps camera and 4X800 or 3200 on a m4/3 camera.

You are applying the crop factor conversion the wrong way round.

ISO 800 on APS-C is equivalent to ISO 1800 on FF.

Also, you cannot compute an equivalent ISO setting and then compare the numbers as if they pertained to the same sensor size. Of the above ISO 800 and ISO 1800 figures, neither represent higher sensitivity than the other; they are equivalent, i.e., they have the same effect on the ability to capture light and the respective noise level.

The larger sensor is more sensitive to light - a great feature in my opinion.

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.

This apparent exposure loss is not a problem, as increasing ISO on the FF sensor accordingly does not cost image quality (remember FF ISO = 2.25 * APS-C ISO).

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.

Note, however, when you convert an FF ISO 100 setting to APS-C, you'll get ISO 44, which no APC-C camera on the market offers. Hence, in practice the larger sensor gives you more higlight protection potential, i.e., higher dynamic range.

[DavidSKAF3]

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 is one reason why I have not purchased a lens like the 15mm f/4 or 21mm f/3.2 as yet. I see the rave reviews, and I want to, but I don't quite understand all these comparisons and conversions, and the basic rule of thumb I gleaned from beginner books like Understanding Exposure is that faster is always better. So I started with the budget 50mm f/1.8 of course, which was too long it turned out. The 35mm f/2.4 is better for what I do, but not ideal. It isn't wide enough. But it quickly became clear using them that these two lenses allow me to use lower ISO's and along with faster shutter speeds. I sometimes wonder why a few of the more expensive lenses are often slower, although to be fair, often only slightly. I think I'd enjoy the 14 f/2.8 more than the 15 f/4 for this reason, but it's hard to ignore what actual users say about both! Right now IO figure I have a lot to learn, though, so I figure I should master the lenses I already own before carping about stepping up and spending even more!


Thank You,


Dave


Here is my very first shot with a DA 35mm f/2.4. As a newbie, I was very pleased! But I gather it will become a bit less than ideal on a FF camera? Do you think used DA lens prices will plummet, while used F and FA lens prices will surge when this new FF Pentax camera is rolled out?

[normhead]

The FF gives you a lot more potential... but since for example an ISO of 100 on APS-c gives you a great picture and you can use that. It doesn't matter if you can get as good a picture at say 1600 ISO on an FF. You got the picture you wanted. And the ISO 1600 on the FF will still not have the same dynamic range. The 14 EV DR of a K-5 isn't matched by many of the FF cameras on the market, as I found out yesterday using my old K20D, more Dynamic Range can let you comfortably use lower exposure values, say going to -1 EV in your exposure, which if it suits your picture gives you an addition stop of ISO. There are a lot of factors involved here and it's way more complicated than just FF gives you more options.. it does, but often those options come at a price. Shooting at higher ISO, the cost is less Dynamic Range and loss of resolution. Shooting FF means narrower depth of field, which is great if that's what you want, not so great if you want the widest possible Depth of Field. I hate to see these statements put out there as stand alone, that are so dependent on unstated ifs, ands, or buts, to be true.

The truth is, if there was some law saying in order to make a statement, you had to explain every factor relevant to the truth of that statement, most of us wouldn't be saying much. It would take too long to make even the simplest point.

[Class A]

It doesn't matter if you can get as good a picture at say 1600 ISO on an FF.

"... say 1600 ISO"? Really?

Given the same sensor technology, ISO 225 would be the equivalent value on FF. The FF camera would then have over a stop more dynamic range. You don't need to go higher than ISO 225. If you arbitrarily choose "1600" that is not true anymore, but you cannot make meaningful comparisons by using vastly different settings.

The 14 EV DR of a K-5 isn't matched by many of the FF cameras on the market,

The D810 has more dynamic range.

There are a lot of factors involved here and it's way more complicated than just FF gives you more options.. it does, but often those options come at a price. Shooting at higher ISO, the cost is less Dynamic Range and loss of resolution.

You don't have to shoot at higher ISO, though. The negative consequences apply to both formats and there is no need to use higher ISO on an FF camera (don't let the higher numbers confuse you, just like f/4 on FF shouldn't make you think you have less DOF compared to f/2.8 on APS-C).

EDIT: The following contained uses of "narrower" which I mistakenly read as "deeper" because the standard term is "shallower", not "narrower". I meant to keep using normhead's term, but thought he wanted it to mean "deeper". My bad. Hence the substitutions in the below.

Shooting FF means narrower depth of field, which is great if that's what you want, not so great if you want the widest possible Depth of Field.

Shooting FF does not mean narrower deeper depth of field.

If you use the same lens (i.e., not an equivalent lens) with the same settings on both formats then the larger format will provide narrower deeper DOF, but the angle of view (the framing) will be very different as well. It really does not make sense to compare the DOF of such vastly different images. If you choose the same framing (have the same part of the scene captured) then the larger sensor does not yield a narrower deeper DOF (and gives you the option of giving you a shallower DOF, provided you have the respective lens).

[Class A]

Which lenses are they?

There are many; just a few examples:

For the following FF lenses --

• 85mm f/1.4
• 77mm f/1.8
• 55mm f/1.4
• 50mm f/1.2
• 31mm f/1.8

-- the following lenses that could yield the same images on APS-C respectively do not exist:

• 57mm f/0.9
• 51mm f/1.2
• 37mm f/0.9
• 33mm f/0.8
• 21mm f/1.2

Or take a standard zoom like the 70-200mm f/2.8 on FF. There is no APS-C lens that could take the same images because it would have to be a 47-133mm f/1.9 lens.

Even if you wouldn't shoot such a zoom at f/1.9 on APS-C, shooting it at f/2.8 would mean you could shoot a f/2.8 lens on FF at f/4, i.e., a full stop away from wide open, yielding considerably better image quality. There is a price, of course, because the f/2.8 lens on FF is bigger, heavier, and more expensive than the f/2.8 lens on APS-C.

[normhead]

"... say 1600 ISO"? Really?

If you use the same lens (i.e., not an equivalent lens) with the same settings on both formats then the larger format will provide narrower DOF, but the angle of view (the framing) will be very different as well. It really does not make sense to compare the DOF of such vastly different images. If you choose the same framing (have the same part of the scene captured) then the larger sensor does not yield a narrower DOF (and gives you the option of giving you a shallower DOF, provided you have the respective lens).

Funny, I once shot a small flower with a ruler, a 50mm lens to represent the FF camera and a 35 on 16 a K-5, to represent the APS-c, at the same settings and used the same framing, and got twice as much DoF with the 35 from exactly the same tripod mount position and ƒ-stop. So, I'm not sure what you just said up there but it doesn't apply to my experience with real world shooting.

If you use the same lens (i.e., not an equivalent lens) with the same settings on both formats

And why would you do that? No one would do that. You go for the shot you want with the equipment you have, and you pick the right lens for that format.
It sounds an awful lot like..." if you don't agree with what I say , I can think of some stupid scenario where I'm right and you're wrong." Me I just stick to the obvious usage. If I wanted to do that I could easily say, if you shoot from 6 inches away with an FA 50 on FF, and A DA 35 2.4 on and APS-c, you're FA 50 won't even focus close enough and you can't even get an image so therefore APS-c is better. Anyone can make up a scenario where one format is better than the other. But what's the value in that?

I think I should have left you on ignore. Oh wait, I did, I just made the mistake of peeking.

[jsherman999]

"[I]

If you use the same lens (i.e., not an equivalent lens) with the same settings on both formats then the larger format will provide narrower DOF, but the angle of view (the framing) will be very different as well. It really does not make sense to compare the DOF of such vastly different images.

Hi Class A, Either you have this swapped or I'm simply confused by your wording (possible.) The same lens, same settings (f-stop) from the same distance, on FF and aps-c - the aps-c shot will have 1.2 stops less DOF, but will be framed 1.5x tighter (i.e. be a completely different shot, so your point about comparing DOF in radically different framing is right.)

Or by 'same settings' do you mean 'same physical aperture' and not 'same f-stop'?

If you choose the same framing (have the same part of the scene captured) then the larger sensor does not yield a narrower DOF (and gives you the option of giving you a shallower DOF, provided you have the respective lens).

Backwards again? Same framing/FOV (say, 50mm on FF vs 35mm on aps-c, same stop, distance) the FF image will have less DOF.

I'll paste the 'cliff's notes' below, I had to refer to them myself to check my sanity just now

• For an equivalent field of view, an APS-C crop sensor camera has at least 1.5x MORE depth of field that a 35mm full frame camera would have - when the focus distance is significantly less then the hyperfocal distance (but the 35mm format needs a lens with 1.5x the focal length to give the same view).

• Using the same lens on an APS-C crop sensor camera and a 35mm full frame body, the a APS-C crop sensor camera image has 1.5x LESS depth of field than the 35mm image would have (but they would be different images of course since the field of view would be different)

• If you use the same lens on a APS-C crop sensor camera and a 35mm full frame body and crop the full frame 35mm image to give the same view as the APS-C crop image, the depth of field is IDENTICAL

• If you use the same lens on a APS-C crop sensor camera and a 35mm full frame body, then shoot from different distances so that the view is the same, the APS-C crop sensor camera image will have 1.5x MORE DOF then the full frame image.

• Close to the hyperfocal distance, the APS-C crop sensor camera has a much more than 1.5x the DOF of a 35mm full frame camera. The hyperfocal distance of a APS-C crop sensor camera is 1.5x less than that of a 35mm full frame camera when used with a lens giving the same field of view.



.

[starjedi]

There are many; just a few examples:

For the following FF lenses --

• 85mm f/1.4
• 77mm f/1.8
• 55mm f/1.4
• 50mm f/1.2
• 31mm f/1.8

-- the following lenses that could yield the same images on APS-C respectively do not exist:

• 57mm f/0.9
• 51mm f/1.2
• 37mm f/0.9
• 33mm f/0.8
• 21mm f/1.2

Or take a standard zoom like the 70-200mm f/2.8 on FF. There is no APS-C lens that could take the same images because it would have to be a 47-133mm f/1.9 lens.

Even if you wouldn't shoot such a zoom at f/1.9 on APS-C, shooting it at f/2.8 would mean you could shoot a f/2.8 lens on FF at f/4, i.e., a full stop away from wide open, yielding considerably better image quality. There is a price, of course, because the f/2.8 lens on FF is bigger, heavier, and more expensive than the f/2.8 lens on APS-C.

If there is an aps-c only K mount, the apps-c lens you mentioned should be possible to make with a similar size and weight. The only reason is that they do not want to make. Theoretically if there is a high quality speed booster with proper aps-c mount, you can even use the ff lens to achieve the goal. No magic.

There always have trades-off between portability and IQ. Comparing to 135mm format as known as cropped full frame, medium frame format is better for the same reason especially for landscape where the large aperture is not needed typically as even f2.8 will be a very large lens for MFT.

[jhmos]

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.

Hmm, that doesn't sound logical. If I try the same full frame lens on a APS-C body or a full frame one, the light intensity at any point on the frame is going to be the same (apart for vignetting). In other words , it shouldn't matter what is sitting at the focal plane as long as it fits in the image circle.
Did you mean with different lenses?

John.