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05-06-2018, 01:39 AM   #1
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My K1 does not give enough "F" (DOF)

Considering that an f/2.8 lens on an APS-C sensor (like on my Nikon Coolpix A, 28mm equiv.) is roughly equivalent to an f/4 lens on a FF sensor (but the one I have on my K1 is a 28mm Zeiss Distagon f/2) and hence my K1 should be able to shoot for instance sunsets hand held while my Nikon should need a tripod:

Why the hell (both cameras set to ISO-100 and focus to infinite) my APS-C Nikon yesterday shot a landscape at f/5.6 and 1/160, while my FF K1 did at f/3.5 and 1/20? (Regardless a FF sensor does have an inherent less DOF than an APS-C sensor, I'm talking about "f vs speed" equivalence).

I assumed that the K1 should improve both parameters or at least one over the other (especially considering the bigger sensor and the much faster lens), but not getting worse both of them!

I could understand that if the Nikon shots at f/5.6 and 1/160, the Pentax would do it at f/6.3 and 1/125 or at f/4 and 1/250, but not at f/3.5 and 1/20 which needs a tripod!

I'm lost.


Last edited by alvaro_garcia; 05-06-2018 at 06:08 AM.
05-06-2018, 01:51 AM   #2
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Try the Pentax in Green mode (Green square). This will eliminate most of the optional settings, and should come close to the Nikon.
05-06-2018, 02:00 AM   #3
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Sounds like you need to change iso to achieve the shutter speed you want when shooting at f6.3. Perhaps iso 400?
05-06-2018, 02:00 AM   #4
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QuoteOriginally posted by alvaro_garcia Quote
taking into account that f/2.8 lens on an APS-C sensor is roughly equivalent to f/2 lens on a FF sensor
aps-c f2 is equivalent to F2.8 on FF

QuoteOriginally posted by alvaro_garcia Quote
Why the hell the same picture on the Pentax is f/3.5 and 1/20 (slightly blurred and less DOF) while on the Nikon is f/5.6 and 1/160 (perfect shot)?
Faster shutter speed and more DOF for the Nikon

If you want to shoot with equivalent settings apsc F5.6 @ 1/160sec iso 100 and for the FF you will need to shoot f/8.4 @ 1/160sec and iso 225 ( remember that you also have to accommodate the iso in equivalent photos)

05-06-2018, 02:18 AM   #5
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When you take the pictures with the Nikon and the Pentax at the same f stop and speed, are both of them at the same brightness?
I suppose the K1 picture is darker. You can change this by setting to exposure compensation accordingly.
05-06-2018, 02:24 AM   #6
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I think you are comparing apples and oranges. Point and shoots have a smaller sensor making it inherently a camera with a deeper DOF. Especially at the wider end of a zoom range. Not that you can't use them for pics just different qualities. The K1 will hands down give you most versatility but you need to study the qualities of both and exploit them when necessary. As far as auto settings go, its what the engineers programmed so live with it or shoot manual. Some people use it as a starting point to get close what manual settings they will eventually choose.
05-06-2018, 02:30 AM - 1 Like   #7
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Different lenses means different T/Stop meaning you can find a difference of 1/3-2/3 of a stop and have to adjust exposure consequently. Also check for Fast/Slow program mode in your camera. Add the fact that actual ISO could be very different from the set ISO (yes your cameras are showing the same Iso setting but there's no certainty that the REAL iso is the same).

Last edited by bm75; 05-06-2018 at 02:47 AM.
05-06-2018, 02:47 AM   #8
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The meter pattern may play a role, in particular if the scene was unevenly lit.

By the way, it would help the discussion if you posted the two images!

05-06-2018, 02:59 AM   #9
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QuoteOriginally posted by alvaro_garcia Quote
...
Why the ...
ISO is the same in both cameras and you wonder why exposure is different
Nikon : f/5.6 , 1/160
Pentax : f/2.8 , 1/20
This is up to a 5 stop difference and it is weird

You mention that the Nikon lens is an f/2.8 and the Zeiss is f/2. This is a significant difference in maximum aperture but maximum aperture makes no difference when the lenses are stopped down (f is bigger). The f/2-ness of the Zeiss lens makes no difference when the lens is set at f/2.8. This paragraph does not help solve your mystery but I thought the infos might be interesting...

One lens might let in more light than another lens. The Nikon lens might transmit more light to the camera. Maybe the Zeiss lens transmits less light because it has more glass elements. When taking a picture with two different lenses that let in different amounts of light, the image brightness should be the same but the exposure settings will be a little different to achieve this.. usually this is not a great difference and the results might be Nikon = f/5.6 , 1/160 & Zeiss = f/5.6 , 1/90. The differences lens light transmission (called t-stop) do not explain the great difference in exposure you have told us about. [also, I am guessing the Zeiss lets in less light to illustrate the point]

I have started exploring a Canon point.shoot and in its AUTO mode it does stuff to lift shadows and whatever other special sauce even if exposure settings are the same as when I use Av with the camera.. Still, no amount of sauce will equal the 5 stops you describe...

As far as the mystery :
Do the Pentax & Nikon pictures look the same brightness on your computer
Do you have exposure compensation set on the Pentax
Do you have something like spot meter set on the Pentax
Try using M mode

Check that both cameras are set for matrix metering. Check that both cameras have exposure compensation set to 0. Use the same scene & light (a wall inside the house even if you need the tripod) and be sure the scene is framed the same. For each camera : set ISO as you have, 100, use M and pick an aperture, use f/4, and then adjust the shutter speed until the camera meter tells you the exposure is correct. Then compare shutter speeds...

Once your mystery is solved, you will find that the Pentax will need about one stop more f to have the same depth of field as the Nikon. The Pentax at f/5.6 should about equal depth of field of the Nikon at f/4 but this all leads to a different discussion... **

You described more depth of field as 'better'. For some people less depth of field is better. To avoid confusion, I might describe more depth of field as 'greater' or 'deeper' and less depth of field as either 'shorter' or 'less'.

** adding the paragraph above about matching DOF : the Pentax to f/5.6 to match the DOF of the Nikon at f/4 means that the Pentax will need a slower shutter speed or higher ISO to offset the bigger F number. But this is about DOF equivalence and has nothing to do with your mystery. Setting aside DOF, a picture of the same scene with the same light and same camera settings should give you a picture of roughly the same brightness and certainly not a picture 5 stops different.]

Last edited by Tan68; 05-06-2018 at 03:12 AM.
05-06-2018, 03:16 AM - 4 Likes   #10
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QuoteOriginally posted by alvaro_garcia Quote
Considering that an f/2.8 lens on an APS-C sensor (like on my Nikon Coolpix A, 28mm equiv.) is roughly equivalent to an f/4 lens on a FF sensor (but the one I have on my K1 is a Zeiss Distagon f/2) and hence my K1 should be able to shoot for instance sunsets hand held while my Nikon should need a tripod:

.
"Equivalence" is bollocks.

The light needed for the same exposure in both formats is exactly the same, you don't multiply or divide it by 1.5 or 2.25 or such nonsense.
05-06-2018, 04:03 AM - 1 Like   #11
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First, OP said that "..distagon f/2". If it is 28/2 Zeiss then it is dead end for handheld landscape shooting. That is one of the most difficult lenses to focus correctly and requires live view at every aperture to get far distance focusing right. Almost the same story for every other distance. If shooting without a tripod is must, then get a mirrorless body to go with the Zeiss to get some idea where it is focused at.

Another issue IF that lens is Leitaxed Zeiss: Light metering is more or less guesswork even with the green button. I had Leitax 28/2 Zeiss and used external light meter to get things right.
05-06-2018, 05:29 AM   #12
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QuoteOriginally posted by clackers Quote
"Equivalence" is bollocks.

The light needed for the same exposure in both formats is exactly the same, you don't multiply or divide it by 1.5 or 2.25 or such nonsense.
Well, it's not me who makes that statement, but many webs which I read along the years. But thanks for your contribution.

---------- Post added 05-06-18 at 05:35 AM ----------

QuoteOriginally posted by Tan68 Quote
ISO is the same in both cameras and you wonder why exposure is different
Nikon : f/5.6 , 1/160
Pentax : f/2.8 , 1/20
This is up to a 5 stop difference and it is weird

You mention that the Nikon lens is an f/2.8 and the Zeiss is f/2. This is a significant difference in maximum aperture but maximum aperture makes no difference when the lenses are stopped down (f is bigger). The f/2-ness of the Zeiss lens makes no difference when the lens is set at f/2.8. This paragraph does not help solve your mystery but I thought the infos might be interesting...

One lens might let in more light than another lens. The Nikon lens might transmit more light to the camera. Maybe the Zeiss lens transmits less light because it has more glass elements. When taking a picture with two different lenses that let in different amounts of light, the image brightness should be the same but the exposure settings will be a little different to achieve this.. usually this is not a great difference and the results might be Nikon = f/5.6 , 1/160 & Zeiss = f/5.6 , 1/90. The differences lens light transmission (called t-stop) do not explain the great difference in exposure you have told us about. [also, I am guessing the Zeiss lets in less light to illustrate the point]

I have started exploring a Canon point.shoot and in its AUTO mode it does stuff to lift shadows and whatever other special sauce even if exposure settings are the same as when I use Av with the camera.. Still, no amount of sauce will equal the 5 stops you describe...

As far as the mystery :
Do the Pentax & Nikon pictures look the same brightness on your computer
Do you have exposure compensation set on the Pentax
Do you have something like spot meter set on the Pentax
Try using M mode

Check that both cameras are set for matrix metering. Check that both cameras have exposure compensation set to 0. Use the same scene & light (a wall inside the house even if you need the tripod) and be sure the scene is framed the same. For each camera : set ISO as you have, 100, use M and pick an aperture, use f/4, and then adjust the shutter speed until the camera meter tells you the exposure is correct. Then compare shutter speeds...

Once your mystery is solved, you will find that the Pentax will need about one stop more f to have the same depth of field as the Nikon. The Pentax at f/5.6 should about equal depth of field of the Nikon at f/4 but this all leads to a different discussion... **

You described more depth of field as 'better'. For some people less depth of field is better. To avoid confusion, I might describe more depth of field as 'greater' or 'deeper' and less depth of field as either 'shorter' or 'less'.

** adding the paragraph above about matching DOF : the Pentax to f/5.6 to match the DOF of the Nikon at f/4 means that the Pentax will need a slower shutter speed or higher ISO to offset the bigger F number. But this is about DOF equivalence and has nothing to do with your mystery. Setting aside DOF, a picture of the same scene with the same light and same camera settings should give you a picture of roughly the same brightness and certainly not a picture 5 stops different.]
Yes, I know it's needed stopping down a higher f/ with the Pentax to get the same DOF than the Nikon.

Besides, both photos look with similar lighting, but the one from the Pentax look with much less DOF than the one from the Nikon.

I will post both once at home and will give you the exposure details.

Besides, the shooting mode was "Auto", but when setting it to "Landscape", the f/ stopped down to 11.

So weird that huge difference...

Last edited by alvaro_garcia; 05-06-2018 at 06:05 AM.
05-06-2018, 06:05 AM   #13
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1) I never saw you mention the ISO used are both cameras set to the same iso? The exposure depends on three factors one of which hasn't been explicitly stated.
2) metered results may vary depending on the program intent. If you really want to compare you should use manual mode on both.
3) as stated, fast lens is only faster at wider f stops. The lenses would be equivalent at the same f stop in terms of exposure.
4) exposure doesn't care about sensor size, but the ladder sensor will generally be able to go to a higher ISO without losing quality, the individual pixels are typically larger and have more light reach each one.
5) T stops are a real thing. T stops are calibrated to take into account light losses for to lens design. F stops simply compare aperture diameter to focal length. However the difference is generally under 1/2 of a stop. That difference mainly is noticed in Cinema when a filmmaker uses multiple lenses in the same scene and doesn't want minor brightness differences to complicate editing, particularly with film.
05-06-2018, 06:07 AM   #14
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QuoteOriginally posted by UncleVanya Quote
1) I never saw you mention the ISO used are both cameras set to the same iso? The exposure depends on three factors one of which hasn't been explicitly stated.
2) metered results may vary depending on the program intent. If you really want to compare you should use manual mode on both.
3) as stated, fast lens is only faster at wider f stops. The lenses would be equivalent at the same f stop in terms of exposure.
4) exposure doesn't care about sensor size, but the ladder sensor will generally be able to go to a higher ISO without losing quality, the individual pixels are typically larger and have more light reach each one.
I have the ISO forced to 100 in both cameras.
05-06-2018, 06:12 AM   #15
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Did you have them at a similar angle of view? Did both images take in the same scene edge to edge? If one was wider or narrower the metering could be with different unless you use spot metering since the matrix style pattern metering can vary based on scene composition. (also I edited my post adding a number 5 btw).

---------- Post added 05-06-18 at 09:13 AM ----------

QuoteOriginally posted by alvaro_garcia Quote
I have the ISO forced to 100 in both cameras.
I missed that. Sorry.
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