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05-02-2016, 06:29 AM   #1
guestk1
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K-1 crop mode

Q: If you use the K-1 with for instance HD PENTAX-D FA 28-105mmF3.5-5.6ED DC WR and turn on APS-C crop mode. Do you get the zoom like a 157mm APS-C mounted lens?

From k-1-lab.com (HD PENTAX-D FA 28-105mmF3.5-5.6ED DC WR) bird picture:

I switched the PENTAX K-1's Crop mode to APS-C setting to capture this telephoto-like image.

05-02-2016, 07:20 AM   #2
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Sort of but not really. The crop mode is just cropping off the edges of the image and keeping the center. The same as you would do in post processing on the computer. So it looks like the image from a longer lens but it is really the same image but only showing the middle.
05-02-2016, 07:30 AM   #3
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It will always be better than a crop done in post though. Because the "zoom" is optical and not done in a software where interpolation will have to take place.
05-02-2016, 09:42 AM   #4
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QuoteOriginally posted by JFk00 Quote
It will always be better than a crop done in post though. Because the "zoom" is optical and not done in a software where interpolation will have to take place.
I don't believe so. A crop*, both in-camera and in PP, simply "trims" pixels from the image with a resulting decrease in field of view. The optical aspect remains the same.

To answer your original question directly, the field of view (FOV) you get from a 157mm (or whatever focal length) lens mounted to an APS-C camera will be the same as that lens mounted to the K-1 in crop mode.


Steve

* The term "crop" in photography goes back to darkroom practice where less than the full negative is printed. In a more general sense, it denotes a cut to make shorter.


Last edited by stevebrot; 05-02-2016 at 09:50 AM.
05-02-2016, 11:56 AM   #5
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QuoteOriginally posted by stevebrot Quote
I don't believe so. A crop*, both in-camera and in PP, simply "trims" pixels from the image with a resulting decrease in field of view. The optical aspect remains the same.

To answer your original question directly, the field of view (FOV) you get from a 157mm (or whatever focal length) lens mounted to an APS-C camera will be the same as that lens mounted to the K-1 in crop mode.


Steve

* The term "crop" in photography goes back to darkroom practice where less than the full negative is printed. In a more general sense, it denotes a cut to make shorter.
Hi (OP here):

Thanks for your reply. I just want to make my question (confusion) a bit more clear:

With a crop of 1.5, a 100mm on a crop camera you will give you 150mm. So, if you put say the FA 70-200mm on the K-1 and turn on crop. Will you get 105-300mm?

Thanks.
05-02-2016, 01:19 PM - 2 Likes   #6
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QuoteOriginally posted by 505515 Quote
With a crop of 1.5, a 100mm on a crop camera you will give you 150mm. So, if you put say the FA 70-200mm on the K-1 and turn on crop. Will you get 105-300mm?
The focal lengths remain the same regardless of the sensor size*. That being said, it is common to read something like "35mm equivalent focal length" in articles or product descriptions with the assumption that the reader is familiar with FOV (and other behaviors) for that focal length on the 35mm (24x36mm) format. That is where the confusion comes in.

The straight and simple answer to your question is that a photo taken with K-1 in crop mode with a particular lens will have equivalent field of view to that same lens on an APS-C camera. FOV will be 2/3 narrower.

If that lens is the D FA 70-200 and you enable crop mode, the lens remains fully 70-200mm. All that changes is the view and how much of the image circle is actually captured. The image below (previously shared here on Pentax Forums) shows this nicely.



Again, all that changes with crop mode is that you are sampling less of the projected image. Yes, that means less pixels...a lot less. OTOH, you also get more apparent "reach" with your lens, meaning that the image captured appears larger in the frame. You can do the same thing later in software and get exactly the same result.

Is shooting a 200mm lens (e.g. the D FA 70-200 at maximum zoom) in crop mode the same as shooting a 300mm lens of similar quality non-cropped on the same camera? In all but FOV, the answer is emphatically NO. To get the same display size the cropped image must be enlarged 1.5x. There are multiple implications, but most immediate and obvious is that the crop mode image is composed of less than half the pixels and is far more more limited in terms of how large the image might be displayed without using data interpolation to fill in the spaces between the pixels.

Full discussion on the earlier thread: Edit: Decided that the other thread was more smoke than light except for the graphic I lifted.


Steve

* Focal length is an optical property of the lens and may be measured on an optical bench with no cameras, sensors, or film present. In simplest terms it is the distance from the midpoint of a simple lens to the plane of focus when the lens is focused to infinity. For complex lenses such as for a dSLR camera, the distance is from the rear nodal point to the plane of focus. (For more than you want to know...CLICK HERE.)

Last edited by stevebrot; 05-02-2016 at 01:29 PM.
05-02-2016, 11:06 PM   #7
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Hi,

Thanks for all your answers.

So.. if I do not want to go with a larger lens to get closer, how about a tele extender? In the K-Mount lens line up there is a hd pentax-da AF rear converter (1.4). Will that work with a FA lens? But give cropped images since its a DA extender? Are there any FA extenders (or planned)?

Thanks.
05-03-2016, 09:42 AM - 1 Like   #8
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QuoteOriginally posted by 505515 Quote
Hi,

Thanks for all your answers.

So.. if I do not want to go with a larger lens to get closer, how about a tele extender? In the K-Mount lens line up there is a hd pentax-da AF rear converter (1.4). Will that work with a FA lens? But give cropped images since its a DA extender? Are there any FA extenders (or planned)?

Thanks.
I suggest starting a new thread on the lens section of this site. There are folk with broad experience using tele converters and I am not one of them.


Steve

05-03-2016, 12:06 PM - 1 Like   #9
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QuoteOriginally posted by 505515 Quote
So.. if I do not want to go with a larger lens to get closer, how about a tele extender? In the K-Mount lens line up there is a hd pentax-da AF rear converter (1.4). Will that work with a FA lens? But give cropped images since its a DA extender? Are there any FA extenders (or planned)?
Theoretically yes. However any tele-converter is going to work better on a fast prime. So using it on the DA*300 works great. Using it on the DA*60-250 works good. Using it on a relatively slow lens like the DFA 28-105 might or might not work. I do not think anyone has actually tested that as yet.

Also, as you note the current HD 1.4x RC is designated DA and Pentax has stated that it will not work with all lenses on FF. What exactly that means is unknown until someone has tested it.

There has been no announcement of any FA or DFA tele-converter at this time.

In short if you are using consumer level zooms IMHO it is better to just get another, longer, zoom. There are any number of film era lenses out there that will provide good images at a fraction of the price of the HD 1.4x RC which goes for over $400.

For example a nice 70-200ish zoom is the Pentax-F 70-210, it is not fast but would not be any different than adding a 1.4x TC to the 28-105 and can be purchased at a significantly lower cost.
05-03-2016, 06:10 PM - 1 Like   #10
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QuoteOriginally posted by jatrax Quote
Theoretically yes. However any tele-converter is going to work better on a fast prime. So using it on the DA*300 works great. Using it on the DA*60-250 works good. Using it on a relatively slow lens like the DFA 28-105 might or might not work. I do not think anyone has actually tested that as yet.

Also, as you note the current HD 1.4x RC is designated DA and Pentax has stated that it will not work with all lenses on FF. What exactly that means is unknown until someone has tested it.

There has been no announcement of any FA or DFA tele-converter at this time.

In short if you are using consumer level zooms IMHO it is better to just get another, longer, zoom. There are any number of film era lenses out there that will provide good images at a fraction of the price of the HD 1.4x RC which goes for over $400.

For example a nice 70-200ish zoom is the Pentax-F 70-210, it is not fast but would not be any different than adding a 1.4x TC to the 28-105 and can be purchased at a significantly lower cost.
The F 70-210mm is a great lens. With the in camera stabilization ability of the K-1 it should be fast enough for most uses. It displays Pentax colors and has a really nice bokeh too. They are fairly reasonable on e-bay. Sellers from Japan seem to have an infinite supply of them in mint or near mint condition for well under $200. As long as the seller has 100% positive feedback as a seller, you can't go wrong buying from them.
05-06-2016, 09:46 PM - 1 Like   #11
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QuoteOriginally posted by 505515 Quote
Hi,

Thanks for all your answers.

So.. if I do not want to go with a larger lens to get closer, how about a tele extender? In the K-Mount lens line up there is a hd pentax-da AF rear converter (1.4). Will that work with a FA lens? But give cropped images since its a DA extender? Are there any FA extenders (or planned)?

Thanks.
Tamron 70-200 f2.8 with the Pentax 1.4 converter the camera went into auto crop mode. Didn't expect that at all. Without the converter FF mode was selected automatically
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