[jeffrey.wetherill]

I used my DA 35mm lens on my K1 today. I took a round of photos using the auto setting (which automatically switched it to crop mode). Then I tried it in FF mode and it worked fine. I looked at both sets of photos, but really couldn't tell any difference. My understanding is that using a DA lens on the K1 will reduce an image to 15 megapixels? Is that correct? And if correct, what does that technically mean? Also, will using a DA lens on the K1 in crop mode reduce the quality of an image? Many thanks for any insights you have might regarding this.

Jeffrey
wethersnaps.com

[alcvet]

Although it is a DA lens, the smc Pentax-DA 2.4 35mm AL covers the full frame sensor without any problems, so this is why you wouldn't notice any problems in ff mode. If you had tried the same with some other DA lenses, e.g. the 18-55 kit lens, you would have seen marked vignetting in ff mode.

My understanding is that using a DA lens on the K1 will reduce an image to 15 megapixels? Is that correct?

[/B]Using crop mode reduces the amount of sensor that you are using to record the image, so yes, reducing it down to about 15MP.

Also, will using a DA lens on the K1 in crop mode reduce the quality of an image?

- it will mean that you have a 15MP image, rather than a 36MP image

[UncleVanya]

Do this. Stand in front of a building like your house/or another building. Set the camera to FF mode. Frame it so that some easy to identify feature is on each edge. Now without moving from that spot switch to cropped mode. Take another shot from there. The edges should show a narrower view of the house.

[jatrax]

My understanding is that using a DA lens on the K1 will reduce an image to 15 megapixels? Is that correct?

No that is not correct. Using the K-1 in crop mode will produce approximately a 15mp image but that has nothing to do with the lens.

DA lenses are (mostly) designed to work on APS-C sensors and thus on the K-1 only cover part of the sensor. However, SOME DA lenses do cover all or nearly all of the FF sensor. The DA 35mm is one and if used on the K-1 in FF mode will produce full size images with minimal vignetting. Other DA lenses however might produce severe vignetting. But in all cases you can put the camera in FF mode and shoot, just understand you will get a vignetted circle on lenses that do not cover the FF image circle. You just crop in post to whatever that lens will produce. There is no hard rule on what part of the FF image any particular lens might cover.

[Na Horuk]

1) DFA lenses work on FF 100%.
2) Some DA lenses work on FF, but some have dark/very low quality edges.
3) Because of the dark edges, it makes sense to crop. Crop just means to cut off the edges
4) The crop mode automatically cuts off the corners (or doesn't even record them) according to APSC sensor size (to about 15-16MP)
5) You can search the thread here or use this function to check which lenses are FF, or you can just look in the viewfinder and decide whether you want to crop or not
6) If you shoot raw, you can crop in post. You can crop as little or as much as you want. You can crop to APSC or you can crop a less or more.
7) The Auto crop mode will use an internal database to decide which lenses should be cropped. Or you can choose the setting manually.

Because the edges get cut off, the amount of MP becomes reduced, and the apparent Field of view looks different. Its like taking a postcard and cutting off the sides.

Hope these bullet points illuminate the issue a bit more

[surfar]

With Firmware V1.3 the 1:1 square crop was introduced, this cut plenty of vignetting out from the shunned 18-55/50-200?16-45 and plenty of others.


The 18-135 was the worst DA(that I own) but in !:! its almost OK, just a touch more cropping in post for useable images.


So a higher megapixel count than aps-c crop is achieved.


Crop mode is 36mp divided by the square of the crop....36over 2.25 in round figures so "crop" mode is closer to 16mp than 15.

[pschlute]

Because the edges get cut off, the amount of MP becomes reduced, and the apparent Field of view looks different. Its like taking a postcard and cutting off the sides.

You are correct, but it is how we view the resultant image that is important.

On a computer screen in full-screen mode, the "cropped" picture (postcard with the edges cut off) will still fill the screen, but because the image has a smaller field of view all the objects in it appear larger on our screen. It is actually like taking a postcard, cutting off the sides, putting the postcard on a photocopier, and printing it at 150%.

This is what gives the impression that a lens on a aps-c camera (or a K1 in crop mode) has a "longer apparent focal length". It does not. It is simply that the image as viewed is "enlarged" more.

[jeffrey.wetherill]

Thanks everyone for your helpful comments. Given the technical aspects of how a DA lens works on a FF K1 (in crop mode), how does it impact image quality? Is image quality degraded when you use a DA lens in crop mode?

Many thanks,

Jeffrey
wethersnaps.com

[UncleVanya]

Thanks everyone for your helpful comments. Given the technical aspects of how a DA lens works on a FF K1 (in crop mode), how does it impact image quality? Is image quality degraded when you use a DA lens in crop mode?

Many thanks,

Jeffrey
wethersnaps.com

Not more than taking the shot with a full frame lens and the cropping it to that same size.

[GeneV]

The square crop was a great addition. I was using FF mode to get the same flexibility and wasting some gigabytes. It seems that it is usually wide angle APS-C lenses or zooms at wide which fare the worst.

[pschlute]

Thanks everyone for your helpful comments. Given the technical aspects of how a DA lens works on a FF K1 (in crop mode), how does it impact image quality? Is image quality degraded when you use a DA lens in crop mode?

Many thanks,

Jeffrey
wethersnaps.com

Your 35mm DA lens will cover the full frame (some DA lenses do not), so you have the choice to use crop mode or not.

Using it in crop mode will not degrade the image, but it may not be suitable for the view that you want to capture, as it has a narrower field of view.

As an example say you want a picture of a church with a little foreground and sky in the scene. You take two pictures of the church from the same position one in crop and one in full frame. The crop mode has just the right amount of foreground/sky that you want but the FF picture has too much. So on your computer you crop the FF picture (without changing any resolution settings) so it looks identical to the crop-captured image.

What you now have are two pictures that have the same size in pixels (WxH) and the same field of view. They both show an image captured by the same part of the sensor ...ie the centre aps-c sized rectangle.

Does this make sense now? There really is no magic involved when using a different part of the sensor (aps-c or square)

[Kunzite]

Different but equivalent ways of cropping to APS-C:
- use an APS-C camera
- use an APS-C lens and let the camera crop
- use a FF lens and set the camera to crop to APS-C
- crop from your favorite image processing software
- print, then use a pair of scissors to cut the borders of the printed paper
Cropping is nothing special, it's just getting rid of the borders.

[jatrax]

Given the technical aspects of how a DA lens works on a FF K1 (in crop mode), how does it impact image quality? Is image quality degraded when you use a DA lens in crop mode?

It has no impact on image quality at all. It can impact image SIZE if you have to crop to get rid of a vignette, but the pixels you do get are not degraded in any way.

Some might argue that a DA lens even cropped will produce a better image than an FA lens that covers the full image circle but was designed for film not digital. But I think that is far too general a statement. Good glass is going to produce good images within the limitations of the image circle it covers and the design flaws of the particular lens. This ignores any field of view considerations that would change the IMAGE but not the IMAGE QUALITY.

The lens is just glass (and other bits) that you put in front of the sensor. It does not matter to the image pixels collected whether the lens says 'A', 'F', 'FA', 'DA' or 'DFA'. The only thing that matters is the quality of the glass and coatings. The size of the image circle does however restrict the size of the image that is projected onto the sensor. If the image circle is large enough then the whole sensor gets used, if not then the image is vignetted.

I think it would be safe to say that using a high quality DA lens in crop mode (or not in crop mode that really makes no difference) will produce a better image quality than using a poor FA lens even though it covers the whole image circle.

[UncleVanya]

Different but equivalent ways of cropping to APS-C:
- use an APS-C camera
- use an APS-C lens and let the camera crop
- use a FF lens and set the camera to crop to APS-C
- crop from your favorite image processing software
- print, then use a pair of scissors to cut the borders of the printed paper
Cropping is nothing special, it's just getting rid of the borders.

I'm going to say we agree on most of these but the one I highlighted is in contention. My short version objection to this is:
If I cut the pictures and they were printed at the same size I don't have a good comparison.
Typically the two prints would need to be different sizes for this to work. If you print the FF version at 12x15 vs. the APS at 8x10 then this holds up. Otherwise you end up with two very different prints due to size.

[Kunzite]

But I wasn't comparing a "FF" and an "APS-C" print; I was only talking about cropping. And I think (hope) it's obvious that you'll get a smaller print after cutting away its edges