lunar module wrote:
Question (for my education, if anyone is willing): Is there any technical difference (such as effective dynamic range, DOF, high iso noise) between acquiring an image on a high res FF sensor in crop mode vs acquiring the same image in FF mode and then cropping the FF image to the exact same boundaries as the image acquired in crop mode? Are these technically identical images or fundamentally different?
No, you won't lose any DR etc. However, you're obviously much, much better off capturing, even roughly, using the entire sensor and you'll technically achieve a better result as you're working with more data.
I've been through this for years as I, like a thousand others, need a fast-ish, ,small-ish 35mm ish lens for Sony.
I've concluded a crop sensor body with something like a Sigma 1.4/35 would be better than an S35 crop on a 7R.
Or, gulp, an RX1R, which always seemed so, so silly to buy an expensive camera solely for the purpose of attaining a particular lens.
But if you only have one body and don't want to add another, yeah, an 16mp (or whatever it is) crop 'will do'.
Melindra wrote:
I've concluded a crop sensor body with something like a Sigma 1.4/35 would be better than an S35 crop on a 7R.
Isn't there a bit of a tradeoff between resolution and noise/high ISO performance between these two options?
For example, compare the results of using the Sony 24mm 1.4 on an A6500 vs on an A7R3 in crop mode.
The A6500 would have 24MP resolution while the cropped A7R3 would have 18MP, right? So resolution would be better on the crop sensor body.
But the photosites on the crop sensor body are physically smaller than the photosites on the cropped FF sensor, so the noise and high ISO performance should be better on the cropped FF images than on those from the crop body.
I usually use crop mode (A7R3) and take portraits of my sons, with Eye AF and face detection ON.. As far as I see at 200% zoom in Photos, on LG 4K monitor, the eyes look so sharp, at least sharp enough for me.
Crop mode at 1.4, shot RAW and converted to JPEG by Apple Photos, no change.
FYI, if you shoot RAW at crop mode with A7r3, the file size gets around 18.5 MP... perfectly fine for me, since sometime I see 42MP is huge and overkill.
Melindra wrote:
But if you only have one body and don't want to add another, yeah, an 16mp (or whatever it is) crop 'will do'.
For me this is more of theoretical interest than based on trying to make do with limited options. I own an A7R3, A9 and A6500 and I also have both the Sony 24mm 1.4 GM and the Zony 35mm 1.4 ZA lenses. I am happy with both of them, but I find the 35 to be bigger and heavier than I prefer for carrying around for hours at a time whereas the 24 is a featherweight and a pleasure to carry around for extended periods of time.
The genesis of my original question was me doing a thought experiment as to whether the 24 could be effectively used as a "twofer" lens without sacrificing too much in the way of quality (understanding that it could not be used in crop mode as a landscape lens or in other high res applications). In my dreams, I could walk around with the wonderfully lightweight 24 lens on the camera and simply push the crop button whenever I wanted a 35mm FOV and still get high quality images. And when I wanted the wider FOV, I could just push the crop button again and be shooting high resolution shots at 24mm. I know there is no free lunch, but it seems as though this might be a compromise worth making in some circumstances.
I guess what I was really hinting at is that I would love to see one of Fred's detailed lens comparos in which he compared the Zony 35mm 1.4 ZA in FF mode vs the Sony 24mm 1.4 in crop mode, but I don't want to seem presumptuous since I know that these comparos require significant time and effort. I would do it myself, but I don't have a clue as to how to do it properly. If it is obvious that such a comparison would be silly, I apologize. Curiosity/cat.
lunar module wrote:
Isn't there a bit of a tradeoff between resolution and noise/high ISO performance between these two options?
For example, compare the results of using the Sony 24mm 1.4 on an A6500 vs on an A7R3 in crop mode.
The A6500 would have 24MP resolution while the cropped A7R3 would have 18MP, right? So resolution would be better on the crop sensor body.
But the photosites on the crop sensor body are physically smaller than the photosites on the cropped FF sensor, so the noise and high ISO performance should be better on the cropped FF images than on those from the crop body.
Yes, not only does the A6xxx has slightly more resolution, it's capturing more light because the whole lens is being used. The 7R in S35 is throwing away most of the imaging circle.
Sometimes that doesn't translate into actual real-world results, however, when I tested my 7R2 (a few years ago) to my A6K, the A6K delivered better images. Better means, they may be more noisy or have less DR, but looked better somehow.
The lens on the 7R2 was the Sigam 1.4/35 (via MC-11) and the A6K, iirc, was a Sigma 1.4/35 DC (crop lens), or, a 1.8/50, sorry, I can't remember, I tried to match the FOV, I remember that and remember it being very close, so probbaly the 50 on the crop.
I'm not much of a technical guy, because none of that matters, I just go and test and see what the results are, but, this test showed what I think was brought on as a result of 'throwing away' all the light the lens was delivering, but the cropped portion of the 7R couldn't capture, because it was in crop mode.
Now, if I had a SpeedBooster™ on the 7R between the body and the lens, that would help to mitigate the difference in FL/FOV and funnel more of that light toward the area of the sensor that is switched on.
I still have the A6K somewhere and some crop lenses, but I don't have much time, I may attempt to re-do the test and post the results here for you if you're interested?
umsl12 wrote:
Crop mode at 1.4, shot RAW and converted to JPEG by Apple Photos, no change.
FYI, if you shoot RAW at crop mode with A7r3, the file size gets around 18.5 MP... perfectly fine for me, since sometime I see 42MP is huge and overkill.
Thanks for posting that image. Appreciate it.
I'm going to go out and shoot some similar shots when I can and if I can figure out how to post images on this site I'll put some up.
Unfortunately, our skies here in San Francisco have been severely impacted by the tragic Camp fire which is actively burning near Chico, CA. The fire is over 100 miles away, but the smoke has blanketed most of the state and has really fouled our air for the last several days, so just being outdoors (let alone photography) has been difficult.
BTW, my thoughts go out to anyone directly affected by the fires burning in our state - we lost a home last year at this time in the Tubbs fire outside of Santa Rosa under very similar conditions so I know what it's like. Condolences to anyone who may have lost a loved one in these fires. Hopefully the fires will be extinguished soon and people can begin the long and challenging process of putting their lives back together again.
Melindra wrote:
Yes, not only does the A6xxx has slightly more resolution, it's capturing more light because the whole lens is being used. The 7R in S35 is throwing away most of the imaging circle. x
So I'm trying to understand the impact of throwing away part of the imaging circle on the photosites that remain within the imaging circle when using crop mode on a FF camera.
On a FF camera, the entire imaging circle of the lens (or at least most of it) is falling onto photosites in FF mode. Each photosite is getting X amount of light falling onto it.
If you go into crop mode and throw away over half of the photosites I understand that you are also throwing away more than half of the light entering into the camera because the photosites outside of the crop area are no longer being used.
But wouldn't the amount of light falling onto each photosite inside the crop area be unchanged? In other words, wouldn't the illumination of each photosite be the same regardless of whether the camera is being operated in FF vs crop mode?
If this is the case, then wouldn't the light being "thrown away" by going into crop mode be more or less irrelevant in terms of exposure, noise and high ISO performance? The only thing any single photosite "sees" is what strikes it. Whether other photosites are being thrown away wouldn't affect what that photosite sees and therefore shouldn't have any impact on the output of the sites included within the crop zone.
I'm not sure if I'm explaining myself very clearly. Apologies if I'm not.
I guess on a pixel level, no, there shouldn't be any difference, however, if you had a 42mp image and re-sampled (over-sampled?) it to 16 or 18 or whatever the crop is, the resulting image would be significantly more rich in terms of detail, higher signal to noise and possibly (I'm not sure on the technicalities here) even DR as I understand it, down sampling increases DR and/or colour depth.
I once heard an engineer (I think it was Blackmagic Design) explain how an 8K 4:2:2 file can become a 4K 4:4:4 file, because, maths.
All I know is that a 7R2 is very average in S35 in comparison to its FF mode and it's also quite average comapred to an A6K which is a quarter the price, has less weight, is more compact etc.
lunar module wrote:
I think it would be kind of interesting to compare the performance of these two options in the manner that Fred does for other lenses just to see what kind of performance hit, if any, one might see using the 24 in aps-c mode compared to the FF 35 1.4. I don't know how to do this kind of comparo but I might take a stab at it just for fun.
Add me to the list of people thinking about this! I am debating the 24GM vs the 35/1.4 and would love to see a direct comparison between these two. I have the 85GM and love that lens! After seeing some of the samples I am thinking about going the 24GM route now but not sure if 24mm is going to be too wide. Decisions to make.
Might be an apple to orange comparison, but how does the 24GM compare to the 16-35GM at the same focal length in flaring and sharpness at stopped down apertures?
Melindra wrote:
I guess on a pixel level, no, there shouldn't be any difference, however, if you had a 42mp image and re-sampled (over-sampled?) it to 16 or 18 or whatever the crop is, the resulting image would be significantly more rich in terms of detail, higher signal to noise and possibly (I'm not sure on the technicalities here) even DR as I understand it, down sampling increases DR and/or colour depth.
I once heard an engineer (I think it was Blackmagic Design) explain how an 8K 4:2:2 file can become a 4K 4:4:4 file, because, maths.
All I know is that a 7R2 is very average in S35 in comparison to its FF mode and it's also quite average comapred to an A6K which is a quarter the price, has less weight, is more compact etc....Show more →
I may be wrong, but I don't think there is any downsampling going on in crop mode. When the FF sensor is operated in crop mode, the pixels outside of the crop area are simply thrown away. The remaining pixels inside the crop area are no different than they were before the crop. Same size. Same amount of illumination per pixel. There are just fewer of them. So (at least the way I understand it), the cropped image shouldn't have any better DR or signal to noise ratio on a per pixel basis than the FF image.
lunar module wrote:
I may be wrong, but I don't think there is any downsampling going on in crop mode. When the FF sensor is operated in crop mode, the pixels outside of the crop area are simply thrown away. The remaining pixels inside the crop area are no different than they were before the crop. Same size. Same amount of illumination per pixel. There are just fewer of them. So (at least the way I understand it), the cropped image shouldn't have any better DR or signal to noise ratio on a per pixel basis than the FF image.
This is my understanding too. And why I don't bother crop in camera and just do it in post cause sometimes I decide to crop differently later.
I didn't say the crop mode is down-sampled, I said if you normalised the 42mp file by down-sampling, you would end up with an image that is superior to the crop image, even at the pixel level.
The proof is in the pudding though, the best way to prove this is to actually carry out the tests.
seurot wrote:
This is my understanding too. And why I don't bother crop in camera and just do it in post cause sometimes I decide to crop differently later.
But if your shooting 20k images in a few days that is not a option. In all my years I rarely if ever have cropped in post. It’s just something I trained myself to do is use the full frame even regardless of aspect ratio. I shot medium format and 4x5 for years as well all different aspect ratios. Sometimes I have to shoot in crop mode to get a 300mm . One thing not brought up here. Forget the file for a second. Let’s say in my case shooting runway with a 70-200 in crop mode which gives me a 300. Now my lens if filling the frame more so now my AF system is closer to subject and can read faces better for focusing. If not in crop mode and going at 200 your AF won’t be as accurate. Basically your bringing your subject closer in which gives your AF system a better chance to see better and be more accurate. Everything now is 1.5 times closer. Files are not downsampled or anything else it’s just cuts off that extra bit of data now. Folks are making this too complicated it’s like putting a 1.5 black mask over your sensor. You don’t see it but just cuts that off.turns out it’s a 18.5 max file now
I’ve been doing this crop mode on this gig for at least 4 years now as Sony forgot to make a 300mm fast lens. Idiots
Seriously they need to get it together as I hate the 70-200 zoom. I would never buy it as the copy variance sucks on it. I’ve rented it at least 10 times and really only once was it good at 200mm. I’ve have had to back off to 193mm most times. Not sure what’s up with that but we are going OT here.
Now back to subject . I plan on using this 24 in crop mode , I don’t need more than 18 max doing PR crap and it eliminates a zoom for me. In post I just make all files 300 Dpi and 12 inches wide let’s say. My final file will be exactly the same as my crop shots and client would never know. If your doing landscape work than 18 may not be enough for you. That’s your call but for certain venues it’s a very useful feature set. For a wedding shooter this could really work well doing reception stuff as it is for me doing commercial events. Basically same thing different cloths. Lol
NCBY wrote:
I've been waiting for Sony to release a 35mm 1.8 so I can buy a second A7III - got a 85mm 1.8 glued to the first one. This lens though... It seems to open up some new possibilities.
In theory, a 24mm 1.4 on an A7RIII in crop mode would look about the same, right? Has anyone spent some time with this combination in crop mode? I mostly do wedding work and I can live with 18mp, but I can't compromise on AF. The ability to zoom out to 24mm would be a nice bonus.
Works great. I have my C1 button set for crop. I recently compared the cropped (36mm eqiv. ) files from the 24GM against my 40mm 1.2 CV both at 1.4. The GM was sharper so I just sold my 40mm and that was my favorite lens. The 24GM is great on the A7riii, like having two lenses for the price of one. 18mp at 36mm is enough for me. Very light and compact for a GM. Just got my 6.00 screw in metal hood today thanks to Guy's suggestion. Works great.
Back to shooting . I went out today it should I say I escaped all the husband, father, grandkid stuff and told everyone to go pound sand. I’m off so there.
So I went up North and shot 4 of my lenses CV21,35,50 and the Sony 24. I did several shots against each other between the CV 21 and the Sony 24. I’ll get them up soon.
In all seriousness I tested all of these and really have yet to go play in my sandbox with them. I went to my junkyard up in Jerome.
Btw I found some new hoods they are by Haige or Houge but they are rectangular metal screw ins there not cheap like 40 bucks but they screw in and have a locking ring. Waiting for a 52 for my CV 21 which is hard to get off and on but this hood maybe stable enough to use. I’ll report more on this as I try them out in the next couple days
