blackest Loc: Ireland

I think we all have a fair understanding of crop factor, e.g a 50mm lens has a field of view on a aps-c DSLR of 75mm with a crop factor of 1.5 and if that same lens was used on M43 then the field of view would be that of 100mm with a crop factor of 2.

How many pixels do you need for a photo? It's been said that for an 8 by 10 at a normal viewing distance 8Mpix is enough and as image sizes go up and viewing distance increases our eyes resolve less detail so you can print larger without needing more detail, although if you put your nose against the print you would see the decreased quality. Admittedly for me it would be a blur without the right glasses, my close focus is not what it was when I was younger...

I have a 36mpix K1 and a 16Mpix k5 (full frame and 1.5 crop) The pixel pitch is virtually the same although the k1 doesn't have an AA filter to blur the pixels a little so maybe it is a little sharper in practice. So the main difference in these 2 cameras is the area of the sensor. The k5 has a sensor 2/3rds the size of the k1 and a m43 has a sensor a 1/4 of the size of the k1. Ok strictly speaking the aspect ratio is different on the m43 but if you choose to use the same aspect ratio as the SLRs then its about right.

So digital zooming or cropping if i crop with my k1 (it does have a number of crop modes inbuilt) but let's do it in post. If i crop a third from the top and a third from the side. I then have an image with pretty much the same resolution as my k5 if the crop is exactly centered there really is no noticeable difference. The field of view is now that of a 75mm lens if I used a 50mm lens. If I crop by half (2x crop) i'm at the size of an m43 sensor a quarter of the area. 36, 18, 9mpix left in the image so still enough for an 8 by 10 and a field of view of 100mm from that same 50mm lens.

I don't think it's going to be acceptable to crop much further but still that's taken a 50mm lens and allowed a zoom to a 100mm field of view and still given an acceptable result.

You would probably want to use a shorter shutter speed if you were cropping to a 100mm field of view say 1/100th minimum for the 50mm lens as opposed to 1/50th with no crop but that's just 1 stop difference on the minimum 1/2 a stop if you just go to the crop sensor sensor size.

Even with a Zoom lens with a variable max aperture might it be better to shoot wider and crop rather than zoom in and maybe lose a couple of stops of light. You might compensate with ISO but you will be losing dynamic range and increased noise.

So can a shorter fast lens, replace a longer lens, a teleconverter or a zoom? Might it even be better?
What do you think?

mrpentaxk5ii

I have been using Pentax DSLRS for about 12 years, I started with the Pentax 100 D-Super. I know own and use the following Pentax bodies : K10 D, Kr. K5II, K3, K3II, KP, and now the K1 MK II. The K5II is set up with a Sigma 120-400 mm F4.5-5.6 it is my wildlife setup that I used to take the photos posted about a week ago at Bombay N.W.R in DE, of snow geese and and a eagle and also the herons at Assatague state park. The K3, K3II and the K1 I use for event photography. The K1 in crop mode is about 15 mega pixels about equal to the K5 but the pixels in the K1 and Ki MKII are larger than the K5 in both full frame and crop mode, you will loose the amount of pixels used when the K1is in crop mode but the size does not change.

bleirer

One thing that could be relevant is the number of photosites on the sensor that record a given area in the 'world.' So the eye of a bird in the distance would be covered by a certain number of photosites on the 50 mm lens but by many more on a 200 mm lens, assuming the lens is capable. So would the one with more pixels per subject area be better? I think that at 100% pixel peeping you could see the difference but for display the eye can't see any difference unless you fall below a certain number of pixels per inch, let's say 320 for someone with 20 20 vision and a close near vision limit.

blackest Loc: Ireland

K1
Pixel or photosite area is 23.62 µm². The larger the photosite, the more light it can capture and the more information can be recorded. Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor. Pentax K-1 has a pixel density of 4.24 MP/cm².
Sensor: 35.9 x 24 mm
Megapixels: 36.40

K5
Pixel or photosite area is 22.75 µm². The larger the photosite, the more light it can capture and the more information can be recorded. Pixel density tells you how many million pixels fit or would fit in one square cm of the sensor. Pentax K-5 has a pixel density of 4.39 MP/cm².
Sensor size: 23.6 x 15.7 mm
Total megapixels: 16.90

In English The k1 has slightly bigger pixels so cropping to the same angle of view the k1 would have less pixels for the same sensor area and a little less noise but in practice you wouldn't be able to tell which was which. So saying the AA filter may soften the K5 image enough so the k1 looks like it has more detail despite the slightly lower pixel count for the same crop.

I don't feel it's enough of a distinction to make a noticeable difference.

use of a teleconverter 1.4 and 2x results in the loss of 1 and 2 stops of light respectively as well as some image degradation due to the increase in elements and tolerances.
Zoom lenses can be slower and softer , so it may be a well judged crop could result in a better photograph.

jcboy3

It can’t replace it, but it can be used as long as it’s sharp enough.

bleirer

The larger photosite definitely helps with diffraction and noise, as you say gathering more light. But the part I'm not sure about is the 'recording more information' part. A photosite no matter what it's size contributes just a single number to the raw file to represent it's position in the image array. you can view the numbers in programs like rawdigger, but big photo site or small will still give you only one number.

blackest Loc: Ireland

If you are cropping from full frame to the angle of view of a crop sensor dslr if the pixel sites are bigger on the full frame then there will be less of them compared to the crop sensor with the k1 and k5 at crop size its about 15mpix v 16.8mpix so theres potentially more detail in the k5 image. To be fair with the k5 having an AA filter and the K1 not it's probably a wash.

There is no need to get hung up too much with pixel counts as long as there is enough that we don't see individual pixels. Trying to get a field of view of a 200mm lens out of a 50mm would be a crop factor of 4 or 1/16th of the sensor area. divide 36 by 16 gives about 2.25 Mpix way less than the 8mpix needed for an acceptable resolution.

imagemeister Loc: mid east Florida

YES, you have the correct idea here !

I have been using Sony's Clear Image Zoom for about 5 years now and I love it ! You do need to Maximize/optimize the native IQ of whatever you are using to get best acceptable results. You can do the same as CIZ with a non-Sony camera by cropping out side the camera and use well applied pixel enlargement software also.
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Picture Taker Loc: Michigan Thumb

I have two cameras that are my most carried cameras. I have a 5DIV and a 7DII I think of my 5b as the wide angle and my 7 as my telephoto camera. This is not factual but I 1.6 times the length with the 7.

RGG

Only reason I can think of to use digital zoom is if there would be no way to crop the image later in a photo editor. Otherwise the photographer can make a more creative crop later in an editor than the camera ever could on its own.

Picture Taker Loc: Michigan Thumb

Digital ZOOM IS the camera going the crop.

RGG

That's the point. All the camera does is crop. Its not really any kind of zoom at all, and crops are more flexible and effective in Post Processing unless one does not have the tools.

blackest Loc: Ireland

Really in post is where to do it. Our cameras have enough resolution that we can crop to what we want.

E.g you could have an f1.4 50mm and be able to crop up to a field of view of a 100mm with no visible degradation. Admittedly if that is your intention you might want to restrict your minimum shutter speed to 1/100th. If your best 100mm is F2.8 then you gain 2 stops by using the 50mm and cropping, now that can be useful.

imagemeister Loc: mid east Florida

The Sony CIZ goes to 2X with pixel enlargement IN CAMERA - no pixel loss - uses an AI algorithm to do it.
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