[Digitalis]

I used a pentax digital spotmeter and compared the reflected metered results from the K10D's integrated spotmeter and I can say it's almost as accurate (within the metering range) as the digital spotmeter, though that spotmeter can measure accurately much lower on the EV scale than the K10d's metering system does. 125/s F/8 ISO100 means the same exposure regardless of wether you are using 8X10 or 110 format ( and providing you are using a lens with the same FOV and a similar optical design)....however, I have encountered lenses that have had aperture settings that were slightly slower/faster than what was etched on the barrel so you have to factor in inconsistent f ratios because the aperture controls the intensity of the image at the film/sensor plane and if the aperture isn't calibrated then that can be a cause of exposure inconsistencies.

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Last edited by Digitalis; 09-24-2009 at 03:48 AM.

[lol101]

I invite you all to:

1. Take an incident light reading with a hand held meter of the same light as that falling on your subject.

2. Set your APS-C dSLR manually to the appropriate combination of ISO, F stop and shutter speed (e.g., 1/500 @ f 11 at ISO 200 for a front lit subject on a bright sunny day).

3. Shoot.

Just done that with my Canon 1000D rock bottom APS-C camera and my good ol' Polaris lightmeter...

Your photo will be underexposed.

Nope. It's fine.

And, for good measure, I did the same with my 5D (rock bottom FF camera ) and guess what: same exposures=same pictures, both perfectly fine!


Now did I get the exact same results? Nope, the 5D is less noisy by about a stop but has less dof too since I dialed the same f-stop on the 50mm as I did for the 35mm on the 1000D.

Now if I want to get the SAME picture, I have to dial an extra f-stop up for the 5D, which comes at the expense of an extra ISO stop.

And what do I get then?

Pictures almost impossible to tell apart, yet one comes from a 1700€ FF DSLR, the other from a 350€ APS-C.

The only advantage to owning a FF is when you run out of f-stops on your lenses and still need that higher shutter speed for a given shot, in other terms, it only shines when you just can't get an equivalent setting with an APS-C setup.

I can get a better picture in low light using my 50f1.4 @f2 ISO 1600 on the 5D than I would using the 35f2 @f2 ISO1600 because ISO 1600 is less noisy on the 5D BUT I will sacrifice some dof to get it.

And if I can live with the further reduced dof, I have the option to go to f1.4 on the 50 and get the ISO down to 800 or up the shutter speed which I just can't do with my 1000D+35.

FF only shines (and moderately so) when you have your back to the wall by offering you more options. For "everyday use", FF offers no advantage per se.

[falconeye]

The only advantage to owning a FF is when you run out of f-stops on your lenses

As I strive for utmost precision in the FF debate, let me add this to this simple statement (I know that you are aware of it):

You are right as far as the noise debate is concerned. But there are two more subtle advantages with FF:
- You may have a tad more dynamic range at the lowest ISO setting (anti noise debate )
- As you stop down on FF for a fully equivalent image, you may have a tad less distortion coming from classical optics aberrations (diffraction is the same).

[Pentaxor]

What do you mean by "different result"? Of course, a DX lens' optical design (whatever be the mount) is such that you have an unacceptable loss of resolution and/or illumination outside the APS-C image circle which would also affect exposure measurement. Spot metering or DX firmware cropping could minimalize the effect.

sorry, what I meant is that we could use a DX lens on a D3x and D700 body. if we are going to compare the photo results of using a FF lens on an FF body and that of a DX lens on an FF body, the results would be different in terms of FOV (FL also?) and DOF due to the difference in lens design or capability made specifically for the particular format that lens is made for. as far as exposure is concerned, they have the same exposure due to what you said firmware cropping and metering with the DX lens?

regarding the DOF difference on the 2 systems, this can be solved adjusting the stops?

just to add, since a DX lens has a crop factor value,so it is necessary to have or use an equivalent lens FL that would match the FOV of that of a FF and aperture speed as well?

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Last edited by Pentaxor; 09-24-2009 at 07:53 AM.

[falconeye]

if we are going to compare the photo results of using a FF lens on an FF body and that of a DX lens on an FF body, the results would be different in terms of FOV (FL also?)

The focal length of a lens is printed on the lens. It cannot miraculously change

The FoV with a given sensor and given focal length always is the same, of course. The FoV is larger with a larger sensor of course, but this larger FoV will not be (fully) usable with a DX lens due to vignetting (black corners) and/or corner softness.

Read:
- FX lens = image circle >= 43mm
- DX lens = image circle >= 29mm but < 43mm
(image circle = diameter of usable area of image when projected onto the focal plane)
There is no other difference between DX and FX lenses.
Note that all Pentax FA lenses are like FX and most DA lenses are DX. Some DA lenses are FX though.

Therefore, the Nikon firmware allows to crop the usable middle area from an image taken with a DX lens.

The black borders will lead to bad exposure meter readings. The Nikon firmware may or may not be able to compensate for this effect.

[Pentaxor]

As I strive for utmost precision in the FF debate, let me add this to this simple statement (I know that you are aware of it):

You are right as far as the noise debate is concerned. But there are two more subtle advantages with FF:
- You may have a tad more dynamic range at the lowest ISO setting (anti noise debate )
- As you stop down on FF for a fully equivalent image, you may have a tad less distortion coming from classical optics aberrations (diffraction is the same).

as far as dynamic range is concerned, isn't the DR of APS-C sensor improving and can be improved to an extent where the FF has no longer an advantage on that department? like the old Fuji S5pro for example has an outstanding DR.

[Marc Sabatella]

I invite you all to:

1. Take an incident light reading with a hand held meter of the same light as that falling on your subject.

2. Set your APS-C dSLR manually to the appropriate combination of ISO, F stop and shutter speed (e.g., 1/500 @ f 11 at ISO 200 for a front lit subject on a bright sunny day).

3. Shoot.

Your photo will be underexposed.

Very possibly, depending on what your expectations are for exposure. What I'm saying is that an FF digital camera would *also* appear underexposed. You're seeing a difference of opinion on metering between you and your meter here (or a difference of opinion on actual sensitivity between the camera and ISO0, not a difference between APS-C and FF.

If a given amount of light strikes a given spot on an APS-C sensor, replacing that sensor with a larger sensor is not magically going to make more light fall on the original spot. This is simple common sense.

Marc, a teleconverter does not change the focal length of the lens; this is an inaccurate oversimplification.

Without a good working definition of "focal length" in this context, I cannot discuss the finer points points of what the difference might be betwene chaging focal length and magnifying an image, but in any case, the point being, magnifying an image optically (what the TC does) is different than cropping.

it would not be possible for a teleconverter of a fixed size with fixed lens elements to alter the focal length of any lens you put it behind, as it would have to be a different size for each different lens to physically alter the focal length of each lens.

I doubt that's true - if it were, internal zoom lenses would be impossible. Physical length of lens is not necessarily directly related to focal length in this way; that's the whole essence of what the word "telephoto" implies (a lens whose focal length is greater than its physical length). But again, given that none of this is actually relevant, and I'm not sure I can define what exactly it would mean to say a TC does or does not change FL, I'll just take a pass on this aspect of the discussion.

[Marc Sabatella]

Suppose you use the SAME FF lens (e.g. a 200mm F4 lens ) on both the FF & APS-C cameras. This means the front element is NOT larger for the FF lens, and that F4 means F4.

If you take a shot of a uniformly white wall, at F4, 1/500 second, then the resulting image will be the same brightness, whether you use FF or APS-C.

Actually, this is a good starting point to illustrate the confusion here. What Falconeye is saying, and what most of this thread has been about, is the fact that while that lens collects the same total amount of light whether used on FF or APS-C, the APS-C csmera is not *using* all of that light. Meaning the camera is quite simply collecting less light. Not less light *per square inch*, but less light total, because there are fewer fewer square inches of sensor to do the collecting. The fact that there is less light in total collected for APS-C is why *for the same aperture, shutter speed, and ISO*, the APS-C camera will show more noise. And it's also why using an f/2.8 lens for APS-C will allow it to collect the same amount of light at a given shutter speed. It will be more light *per square inch*, so you'll need a lower ISO to avoid overexposure. And by lowering the ISO, you get noise similar to what you started with on FF. Furthermore - and this part *does* seem like magic to me - it also works out the DOF for f/2.8 on APS-C and f/4 is the same, if you also change focal length to achieve the same FOV.

Anyhow, all that is just restating what has been discussed in the thread previously. The error being made by 24x36 is in thinking that "collecting less light in total" for APS-C at the same aperture, and shutter speed means you'll get a darker exposure at the same ISO. As I said above, less light above, but not less light *per square inch of sensor*. And exposure is all about light per square inch.

[pingflood]

as far as dynamic range is concerned, isn't the DR of APS-C sensor improving and can be improved to an extent where the FF has no longer an advantage on that department? like the old Fuji S5pro for example has an outstanding DR.

But what keeps you from improving the FF sensors in the same manner?

[Pentaxor]

But what keeps you from improving the FF sensors in the same manner?

the point is, this is more like a rat race. of course they need to improve the FF as well if they want to retain that edge over the APS-C dslrs. it's part of marketing. but as far as feature improvement is concerned, the APS-C dslrs are capable of it and isn't handicapped in any way in that department.

[kristoffon]

I think this discussion is stupid.

For instance I have this lens, a 31mm f/1.8. It is a full-frame lens that's a wide angle. It also has a short DOF.

Is there an equivalent APS-C lens that will give me equivalent FOV (21mm) and DOF (f/1.2)? There is not.

Is there an equivalent APS-C lens that will give me equivalent FOV and light-gathering capability (21mm f/1.8)? There is not.

I don't really care about low noise. I'll get a Pentax FF camera when/if it comes out only so I can have my 31mm become a wide angle.

Low noise is not relevant AT ALL. If it matches the K20D that's enough for me.

NOBODY with a FF cam will stop it down to shorten the DOF of their 31mm f/1.8 camera. That makes the discussion EVEN MORE stupid.

[jogiba]

Also with FF you could use a Sigma 12-24mm zoom with 122° FOV @12mm, The widest FOV zooms for APC DSLRs are about 102° FOV @10mm.

[falconeye]

Is there an equivalent APS-C lens that will give me equivalent FOV (21mm) and DOF (f/1.2)? There is not.
Is there an equivalent APS-C lens that will give me equivalent FOV and light-gathering capability (21mm f/1.8)? There is not.

No need to make a distinction between noise and DoF (this is what this thread was started for). You need a 20mm f/1.2 APS-C to match the FA31.

And I pointed out above that there are other reasons in favour of FF than noise. The lack of wide aperture wide angles is just one of them. So, you are right.

Also with FF you could use a Sigma 12-24mm zoom with 122° FOV @12mm, The widest FOV zooms for APC DSLRs are about 102° FOV @10mm.

I have this lens and it is amazing. However, on film make sure not to have people in the edges (or to shoot portrait orientation) because otherwise, they will look reeeeeaaaally faaaaaaaaaaaat

[Rondec]

Also with FF you could use a Sigma 12-24mm zoom with 122° FOV @12mm, The widest FOV zooms for APC DSLRs are about 102° FOV @10mm.

I can't imagine the level of distortion that would be present on 12mm on full frame. I have to say, that my favorite landscapes are taken with "normal" lenses. To get more field of view, panoramic stitching works better than trying to cram extra angle into a smaller space.

[jogiba]

I can't imagine the level of distortion that would be present on 12mm on full frame. I have to say, that my favorite landscapes are taken with "normal" lenses. To get more field of view, panoramic stitching works better than trying to cram extra angle into a smaller space.